Publication - Strategy/plan

UK dolphin and porpoise conservation strategy: technical report

Published: 22 March 2021
Directorate: Marine Directorate
Topic: Economy, Environment and climate change, Marine and fisheries
ISBN: 9781800048522

The technical report for the proposed UK Dolphin and Porpoise Conservation Strategy, describing the process used to assess the vulnerability of the populations of the nine named species of cetaceans to current pressures in UK waters.

Supporting documents

Section 5 – Confidence Scores and Supporting Evidence

Confidence

30. The confidence in the resulting vulnerability score has been assessed with the aid of a confidence decision tree (Figure 2). The confidence in the vulnerability assessment is based on the available evidence, as to whether the UK population of a species is impacted, or not, by a pressure.

31. There are two main sources of evidence:

the published literature and, specific to the UK,
through UK monitoring of pressures impacting cetaceans.

Evidence

32. At the UK scale, the main sources of evidence regarding the impacts of pressures arise from the Cetacean Strandings and Investigation Programme (CSIP) and associated partners, the Bycatch Monitoring Programme, published and “grey” scientific literature.

33. The level of evidence that these sources provide varies by species; for example, the UK CSIP provides robust evidence for harbour porpoises and common dolphins, and less robust evidence for some other species due to the lower numbers of strandings. A summary of the evidence provided by CSIP is given in Table 3. The evidence is considered robust if there have been more than 100 post mortem examinations (PMEs) over a five-year period for a single species.

34. The bycatch monitoring scheme targets fisheries and areas where the bycatch risk posed to harbour porpoises and common dolphins is highest; therefore, sampling for these species is likely to be much more adequate than for some other species.

35. Table 3 sets out the number of PMEs carried out between 2007 – 2016, inclusive, by CSIP and the Scottish Marine Animal Strandings Scheme (SMASS). Numbers are split by species and the cause of death (where one could be attributed) is provided as a percentage of all PMEs for that species.

Table 3: Summary of evidence from the PME work of the CSIP and SMASS
	Harbour porpoise	Common dolphin	White-beaked dolphin	Atlantic white-sided dolphin	Risso’s dolphin	Bottlenose dolphin	Long-finned pilot whale	Killer whale	Minke Whale
Number of PMEs	691	227	53	27	17	31	68*	4	30
Percentage (%) of PME identifying the particular cause of death
Physical trauma due to vessel collision	2	4	0	0	6	0	0	0	1
Entanglement	0	0	0	0	0	0	0	25	5
Starvation	23	10	20	11	17	10	1	50	0
Bycatch	14	23	2	0	6	10	0	0	0

Note the percentages do not sum to 100; the remainder are causes of death that could not be attributed.

* the high number is the result of three mass stranding events in Scotland involving long-finned pilot whales - Kyle of Durness (2011), Pittenweem (2012) and Western Isles (2015).

Assessing confidence

36. Confidence in the vulnerability assessment has been derived from consideration of the actual impact of a pressure on a species driven by the identified activities, as evidenced by the available literature and monitoring data. In the absence of evidence about the impact, the confidence in the vulnerability score would not necessarily be low, if we have good evidence of the exposure. Evidence of exposure is clearly an important consideration if the pressure/species vulnerability scores are to be appropriately prioritised for action.

Confidence Decision Tree

37. Figure 2 details the Confidence Decision Tree and how the scoring is derived from it. The scoring for confidence is:

H= High;
M= Moderate;

38. The bottom row of the decision tree (Figure 2) indicates the nature of the measure that will be considered for each vulnerability/confidence combination. These outcomes were then considered in the context of current research and the measures already in place to identify where the gaps remain and how best these can be addressed. The nature of the measures refers to:

1 = current measures considered adequate/no measures required;
2 = Further research required;
3 = Additional/new wider-measures to be considered for medium vulnerability;
4 = Additional/new wider-measures to be considered for high vulnerability.
1/2 – indicates that no measures are likely needed but some research may be required to verify that current measures are adequate.

Figure 2: Decision tree used to grade confidence in the vulnerability assessment outcomes.

Table 4: UK Vulnerability assessments and supporting evidence for each species covered by the strategy
Harbour porpoise
Pressures and activities		Evidence supporting the UK assessment	Regional/Local variations where vulnerability likely higher than UK assessment due to increased exposure
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Bycatch in fishing gear (particularly bottom set gillnets) is recognised as the greatest anthropogenic pressure in UK and adjacent waters (Read et al, 2006; ICES 2015a; Northridge et al. 2016), but this varies by region, with the South West being of greatest concern, followed by the North Sea (Northridge et al., 2016). Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. There has been no targeted monitoring of creeling/pots through the current monitoring scheme but evidence from the strandings scheme and of anecdotal records suggest bycatch events in creels and pots are very rare (Northridge, 1988); porpoises may be able to avoid them and therefore this activity is not considered a high risk. There has been some monitoring of drift net fisheries and interactions recorded. No harbour porpoises have been recorded as bycatch in pelagic trawls, despite considerable monitoring. Bycatch is greatest in set nets and these are the focus of the UK bycatch monitoring scheme. There are some regional variations from the UK assessment (Table 4) where exposure and vulnerability are likely higher.
	Drift net fishing		Driftnet fishing is highest in the southern part of the North Sea
	Trawling and purse seining
	Set (fixed) net fishing		Set net fishing is highest in the southwest approaches of the Celtic and Irish Seas.
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time or over an extended time period, the impact is likely to be greater. However, evidence on the population level impacts of cumulative noise (across industry sources) in lacking.	West Scotland
	Seismic or geophysical surveys	Behavioural response of harbour porpoises to noise (pile driving: Carstensen et al., 2006; Brandt et al., 2011; Teilmann and Carstensen, 2012; seismic surveys: Stone & Tasker, 2006; Stone, 2015; Thompson et al., 2013: Deaville and Jepson, 2011; ICES, 2012; Shipping: Heinänen and Skov, 2015). The density of harbour porpoises tends to recover in an area when the disturbance has ceased (Thompson et al., 2013; Brandt et al., 2011). However, the impact of disturbance on fecundity and survival of the species is not well understood.	North Sea
	Underwater explosions		Southern North Sea
	Pile driving		Southern/central North Sea
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al.,2013) to marine mammals. Installations may create foraging opportunities (Scheidat et al., 2011) and return post-construction can be quick; however, there is a single example from long term monitoring of Nysted Offshore windfarm where porpoises had not returned to ‘baseline densities’ 10 years on from construction (Tougaard et al., 2005; Teilmann et al., 2012).
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms. However, the exposure to the pressure is limited.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently placed ADDs associated with aquaculture can show impacts on movement patterns, local density and may cause habitat exclusion (Gӧtz & Janik, 2013; ICES, 2015b). The extent of the impact varies with device (e.g. see Northridge et al. 2013b) with some having greater potential to impact than others. ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels. However, the noise produced from currently used devices, although audible, is at frequencies that are not a significant concern (DeRuiter & Lurton, 2011; Deng et al., 2014) in the context of causing impacts to marine mammals However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce the risk of bycatch. Their effectiveness in reducing harbour porpoise bycatch, effectively by causing a behavioural response, is well documented (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). Extensive pinger use could have detrimental effects through habitat exclusion. However, pingers are currently used only on gillnet vessels ≥12m in length, which is a very small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes, including disturbance, are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Behavioural reactions have been observed in response to shipping (Richardson, 1995; Skov et al., 2014) and reduced porpoise density around shipping lanes of the UK was shown in Heinänen and Skov (2015). Smaller vessels and recreational craft may produce higher frequency noise than shipping and these may also be expected to lead to area avoidance behaviour (IAMMWG et al. 2015). Regionally, vulnerability is highest in areas of busy shipping lanes, such as the southern North Sea. Vulnerability may be higher locally at certain times of the year.	Southern North Sea
	Military activity and sonar	A single case proposes a link with military activities and harbour porpoise mortality (Wright et al., 2013; Siebert et al., 2013) although there are numerous cases in other species, particularly beaked whales. Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall, there is low vulnerability across the UK but regionally high at certain times when operations are occurring.	South west approaches Cardigan Bay and South Pembrokeshire, Wales West Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. The elusive nature of harbour porpoises means it has rarely been subjected to more invasive scientific studies in the UK. Some tagging has taken place in Denmark (e.g. during the DEPONS project, Nabe-Nielsen et al. 2018) and tagging feasibility is being investigated in the Netherlands (Scheidat et al., 2016). Disturbance from research vessels is a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	There are many studies that indicate behavioural impacts from tourist vessel interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). Harbour porpoises are not typically targeted for tourism, but potentially some local disturbance impacts as a consequence of activities targeting other species.
Change to habitat	Barrier to movement	Evidence of changes in habitat due to barriers to movement (e.g. from placement of structures on the seabed) of cetacean species is very limited (ICES, 2015b). In the UK, there is potential for higher exposure to this pressure on the west coast of Scotland due to its complex coastline and impacts on movement that ‘barriers’ might cause. ICES (2015b) recognised that barrier effects may be locally significant but at the UK scale, there is negligible overlap of the pressure and the species.
	Change / removal of supporting habitat	Very few studies of effects on harbour porpoises from changes to or removal of supporting habitat, but may be locally significant. Potential for higher exposure to this pressure and therefore greater vulnerability in the North Sea and Celtic and Irish Seas, where activities such as aggregate extraction and bottom fishing are more concentrated.	North Sea Celtic Sea Irish Sea
	Reduction in availability of prey	Changes in prey availability, due to: competition with other marine predators, fishing or climate change, may have an impact on porpoises (Santos and Pierce, 2003; Santos et al., 2004; MacLeod et al., 2007a; MacLeod et al., 2007b; Thompson et al., 2007). Starvation is a commonly recorded cause of death in stranded individuals (see UK CSIP annual reports: https://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population. There is some recent information on prey preferences (Hernandez-Milan 2014; Andreasen et al., 2017), but information on the implications of changes in prey availability is lacking.
	Localised temperature change	Local water temperature changes (e.g. cooling water discharges from power stations), is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Harbour porpoises tend to avoid vessels (e.g. Heinenan and Skov, 2015) and this may mediate their exposure to the pressure to some degree. However, monitoring of stranded animals shows that vessel strikes are identified as a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). There is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land and so the true extent of this pressure is likely underestimated.
	Collision with renewable energy devices	Few wet renewable devices are currently in place, therefore limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. The demonstration project at MeyGen is carrying out acoustic monitoring around the turbine, collecting data on cetaceans including harbour porpoise, with further surveys planned. Potentially locally significant.
	High energy, acoustic events e.g. explosions	Loud noise explosions can result in injury to cetaceans (NOAA, 2018). For example, the clearance of unexploded ordinance has the potential to cause permanent hearing loss to those harbour porpoise within range of the blasts (von Benda-Beckmann et al. 2015).	Southern North Sea Cardigan Bay and South Pembrokeshire, Wales
Marine pollution	Oil pollution	There are no published records of any spills in which a harbour porpoise was affected. No measurable effect of the "Erika" oil spill was found (Ridoux et al 2004) or the "Braer" spill (Kingston, 1999).
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Jepson et al., 1999, 2005; 2016; Hall et al., 2006; ICES, 2015b). These include impacts on reproductive abilities of harbour porpoises (Murphy et al., 2015).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. Its presence has been noted in harbour porpoises but has not been identified as the acute cause of death (Deaville, 2016).
	Entanglements in marine litter & ghost nets	Little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Common dolphin
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment due to increased exposure
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in the current bycatch monitoring scheme. Bycatch occurs mainly in trawls, but also in set net fisheries, with the primary area of concern being the south west approaches (Deaville and Jepson, 2011; Deaville and Jepson, in press; Murphy et al., 2013; Northridge et al., 2016). Evidence from the strandings scheme or anecdotal records suggest bycatch events in creels and pots are very rare and therefore this activity is not considered a high risk.
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing		South west approaches
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced into the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Goold, 1996; Stone and Tasker, 2006; ICES, 2012; Stone, 2015). Whilst the impact of disturbance on fecundity and survival of this species is not well understood, the distribution of the species means their exposure to the pressure may be less than other species that occur year-round in the industrialised North Sea for example.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) to marine mammals. There is currently negligible overlap of this species and pressure.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there is no evidence to suggest operational platforms have a significant impact on this species. Other studies have indicated that offshore installations may create foraging opportunities for some species (Todd et al., 2009) but there is little overlap of this species with the UK oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently located ADDs associated with aquaculture shows that they can effect cetacean movement patterns (this data is mainly related to harbour porpoise), local densities and lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.	West Scotland
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch. Their effectiveness in reducing bycatch of common dolphin is less well understood (e.g. Northridge et al., 2011) and their success at ‘deterring’ animals from nets is dependent on the signal type and source level (Berrow et al. 2008). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet and hence exposure at UK scale is low.	South west approaches
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Disturbance reactions in cetaceans have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes. Ansmann et al. (2005) reported that common dolphin change the frequency of their whistles in the English Channel, possibly as a response to shipping noise.
	Military activity and sonar	Links have been drawn between mass stranding events and acoustic activity such as military operations (Jepson et al., 2013). Cases of acute and chronic forms of gas embolism, similar to those found in beaked whale strandings associated with sonar exercises, have been recorded, although the cause is unknown (Jepson et al., 2003; Deaville & Jepson 2011). Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	South west approaches North west Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. Disturbance from research vessels is a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with common dolphins elsewhere (e.g. Neumann and Orams, 2006; Stockin et al., 2008; Meissner et al., 2015). However, within the UK the highest risk areas are south-west Wales and south-west England where tourist operations coincide with distribution.	South west
Change to habitat	Barrier to movement	Evidence of changes in habitat due to barriers to movement of cetacean species is very limited (ICES, 2015b). In the UK, there is potential for higher exposure to this pressure on the west coast of Scotland due to its complex coastline. ICES (2015b) recognised that barrier effects may be locally significant but at the UK scale, there is negligible overlap of the pressure due to barrier creating activities and the species.
	Change / removal of supporting habitat	Very little evidence of effects on common dolphin from changes to or removal of supporting habitat, but may be locally significant.	Celtic and Irish Seas
	Reduction in availability of prey	Changes in prey availability due to: competition with other marine predators, fishing or climate change, may have an impact on common dolphins. Starvation is a recorded cause of death in stranded individuals (see http://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population. Common dolphins are opportunistic feeders (Young & Cockcroft 1994) and tend to select prey based on energy densities (Santos et al. 2004, Brophy et al. 2009, and Spitz et al. 2010). They show seasonal changes in prey preferences (Murphy et al. 2013).
	Localised temperature change	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Common dolphins are often attracted to vessels (Canadas et al., 2004). Monitoring of stranded animals suggests that vessel strikes area not a major cause of death for this species (Deaville and Jepson 2011; Deaville 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land, which means events are likely underreported.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.
	High energy, acoustic events, for example removal of unexploded ordnance	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil Pollution	There are no published records of any spills in which a common dolphin was affected. No measurable effect of the "Erika" oil spill off Brittany was found on common dolphin (Ridoux et al., 2004).
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Jepson et al., 1999, 2005; 2016; Hall et al., 2006; ICES, 2015b) with high PCB burdens thought to impact upon foetal survival in common dolphins (Murphy et al., 2012). The levels recorded in common dolphin are not as high as those recorded in other species in UK waters (Jepson et al., 2013).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters (Deaville, 2016).
	Entanglements in marine litter and ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern. Offshore distribution of this species limits their exposure.
Atlantic white sided dolphin
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment due to increased exposure
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Bycatch occurs in midwater trawls (Ross, 2003) and demersal gill nets (Reeves et al., 1999; Morizur et al., 1999; Couperus, 1997, Northridge et al., 2014) although evidence for significant bycatch in UK waters is limited. Bycatch events of small cetaceans in creels and pots are very rare but there has been limited monitoring of these gears. However, given the predominately offshore distribution of this species and coastal nature of creeling and potting and drift-netting, we are confident that exposure is low and these are not considered a high risk to this species.
	Drift net fishing
	Trawling and purse seining		West Scotland
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Stone and Tasker, 2006; ICES, 2012; Stone, 2015). Detections of Atlantic white-sided dolphins were significantly lower during large airgun and avoidance of vessels (Stone et al. 2017). However, it is not well understood what the impact of disturbance is on fecundity and survival of this species.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013). Installations may create foraging opportunities for some species (Scheidat et al., 2011). Offshore nature of this species limits their exposure.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms. Other studies have indicated that offshore installations may create foraging opportunities for some species (Todd et al., 2009).
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently located ADDs associated with aquaculture is limited (this data is mainly related to harbour porpoise) but has potential to effect cetacean movement patterns (ICES, 2015b). Disturbance impacts have been demonstrated for other species (Risch et al., 2017). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury. However, the offshore distribution of Atlantic white sided dolphin limits their exposure.
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet. The predominantly offshore distribution of this species means there is limited overlap with pressure.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015). Dredging and mining are generally a more inshore operation and therefore there is limited overlap with Atlantic white sided dolphin distribution.
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes. However, the predominantly offshore distribution of this species means overlap with busy sea areas is low.
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	North west Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. The offshore nature of the Atlantic white sided dolphin means it is not normally subject to more invasive scientific studies.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist vessel interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). This species is not normally targeted due to the offshore nature of its distribution.
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b) although unlikely to occur given offshore nature of the species.
	Change / removal of supporting habitat	Very little evidence of effects on Atlantic white-sided dolphin from changes to or removal of supporting habitat and are unlikely due to offshore distribution.
	Reduction in availability of prey	Changes in prey availability due to: competition with other marine predators, fishing or climate change, may have an impact. Starvation has been recorded as a cause of death in stranded individuals (UK Strandings annual reports: http://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population. The species has a varied diet with a preference for gadiformes and they adapt their feeding seasonally depending on movement of prey species (Hernandez-Milian et al, 2016).
	Localised temperature change	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature and the offshore distribution of this species; exposure and vulnerability is therefore low (localised).
Physical Injury/mortality	Vessel strikes	Monitoring of stranded animals shows that vessel strikes rarely are a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant. Exposure considered unlikely due to the offshore nature of the species.
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	There are no published records of any spills in which Atlantic white-sided dolphin were affected. Atlantic white-sided dolphins were observed swimming and foraging in the oil slick caused by the Regal Sword (Goodale et al., 1981); however, it is noted that this does not exclude the possibility of short- or long-term health impacts.
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Contaminants have been recorded in Atlantic white-sided dolphin (Reeves et al., 2009) although generally in lower concentrations than in more coastal species (Van De Vijver et al., 2003). However, in blubber samples taken around Greenland, Finland, and the Faroe Islands, PDBE levels in Atlantic white-sided dolphins were markedly higher in the males sampled than in some other cetacean species (Rotander et al., 2012), and varied across years with the peaks around 2000 when production levels were at their highest, indicating the species is susceptible to certain contaminants. In other species, immunosuppression has been reported as a consequence of high contaminant burdens.
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters.
	Entanglements in marine litter and ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), however, exposure to the population is unlikely to be a concern due to their offshore distribution.

White-beaked dolphin
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment due to increased exposure
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in current monitoring scheme. Evidence from the strandings scheme or anecdotal records suggest bycatch events in creels and pots are very rare which suggests that individuals may be able to avoid them and therefore this activity is not considered a high risk. Bycatch events have been recorded in gillnets and cod traps out with the UK (Reeves et al., 1999) and bycatch in pelagic trawl nets in the North Sea has historically been noted as a risk for white-beaked dolphins (Morizur et al., 1999). For the UK, there have been reports of bycatch as a cause of death in stranded animals (Deaville & Jepson, 2011), and a single report of a probable white-beaked dolphin bycaught in a mid-water trawl recorded through the UK bycatch observer programme (Northridge et al., 2016).
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Stone and Tasker, 2006; ICES, 2012; Stone, 2015). Stone et al (2017) document a significant reduction in detection rates and vessel-approaches of the species in response to firing of ‘large seismic arrays’. Rasmussen et al. (2016) reports behavioural responses to a range of sounds elicited during playback experiments. However, the impact of these and disturbance on fecundity and survival of this species is not well understood.	North Sea
	Underwater explosions
	Pile driving		North Sea
	Operational offshore wind farms	Noise from operational wind farms are produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) for marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently located ADDs associated with aquaculture shows that they can affect cetacean movement patterns (this data is mainly related to harbour porpoise), local density and may lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.	West Scotland
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015)
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes.
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. There is some dedicated photo ID surveying occurring in the English Channel. Disturbance from research vessels is a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). Dedicated tours for white-beaked dolphin occur in Lyme Bay and in Northumberland which coincide with their distribution.	Lyme Bay, south coast England North east England
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b).
	Change / removal of supporting habitat	Very little evidence of effects on white-beaked dolphin from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability due to: competition with other marine predators, fishing or climate change, may have an impact. Starvation has been recorded as a cause of death in stranded individuals (see UK Strandings annual reports: http://ukstrandings.org/csip-reports) but there is no understanding of cause in the population. White-beaked dolphins have a varied diet (Fall and Skern-Mauritzen, 2014) and are known to feed on at least 25 different fish species, many of which are commercially targeted by fisheries (e.g. whiting and cod) (Jansen et al, 2010; Jansen, 2013).
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Monitoring of stranded animals shows that vessel strikes rarely are a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.	Scotland
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	There are no published records of any spills in which white-beaked dolphin were affected.
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Jepson et al., 1999, 2005; 2016; Reeves et al., 2009; ICES, 2015b). White-beaked dolphins were found to have one the highest levels of perfluorinated organochemical loads of the marine mammal species stranded along the southern North Sea coast (Van De Vijver et al., 2003).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters.
	Entanglements in marine litter & ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Bottlenose dolphins (offshore)
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in the current monitoring scheme. There have been reports of bycatch of bottlenose dolphins occurring in static nets (Reeves et al., 2009; Deaville & Jepson, 2011; Northridge et al., 2016). Evidence from the strandings scheme and anecdotal records suggest bycatch events in creels and pots are very rare.
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Stone and Tasker, 2006; ICES, 2012; Stone, 2015). However, the impact of disturbance on fecundity and survival of this species is not well understood.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013).
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently located ADDs associated with aquaculture show they can effect cetacean movement patterns (this data is mainly related to harbour porpoise), local density and may lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al, 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). They have proved to be effective in disturbing bottlenose dolphin away from nets (Leeney et al., 2007). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes.
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring .	North west Scotland South West Approaches
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Overall, limited in UK waters with certain activities requiring licensing. However, the coastal populations of this species are highly targeted by research. Disturbance from research vessels is, however, a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	The inshore groups are heavily targeted by wildlife watching boat tour; the offshore bottlenose is not.
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b).
	Change / removal of supporting habitat	Very little evidence of effects on bottlenose dolphin from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability, due to: competition with other marine predators, fishing or climate change, may have an impact. Starvation has been recorded as a cause of death in stranded individuals (see UK Strandings annual reports: http://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population or whether the sampled individuals are from the offshore or inshore population. There is some recent information on prey preferences (Millian-Hernandez et al., 2015) but information on effects of changes in prey is lacking.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Bottlenose dolphins are often attracted to vessels. Monitoring of stranded animals shows that vessel strikes are rarely a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	There are no records of bottlenose dolphin populations being impacted by oil spills in the UK. The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 was linked with unusual mortality events of bottlenose dolphins between 2010 and 2014 (Graham et al., 2017).
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Jepson et al., 1999, 2005; 2016; Hall et al., 2006; ICES, 2015b) with bottlenose dolphin exhibiting some of the highest levels ever recorded. Such burdens are considered likely to have a significant effect at the population level (Jepson et al., 2016).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters.
	Entanglements in marine litter & ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Bottlenose dolphins (inshore)
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in the current monitoring scheme. There have been reports of bycatch of bottlenose dolphins occurring in static nets (Reeves et al., 2009; Deaville & Jepson, 2011, Northridge et al., 2016). Evidence from the strandings scheme and anecdotal records suggest bycatch events in creels and pots are very rare which suggests that individuals may be able to avoid them and therefore this activity is not considered a high risk.
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater (Heiler et al, 2016)..	East Scotland
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Seismic: Stone and Tasker, 2006; ICES, 2012; Stone, 2015; Pile driving: Bailey et al., 2010; Graham et al., 2017). However, the impact of disturbance on fecundity and survival of this species is not well understood.	Cardigan Bay, Wales East Scotland
	Underwater explosions		Cardigan Bay, Wales East Scotland
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms are produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) to marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently located ADDs associated with aquaculture shows they can affect cetacean movement patterns (this data is mainly related to harbour porpoise), local density and may lead to habitat exclusion (ICES, 2015b). Exposure and vulnerability is considered highest on west coast of Scotland. ADDs are sometimes used to exclude animals from an area as a means of mitigating against injury prior to offshore construction and for ordnance detonation.	West of Scotland
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013; Larsen and Eigaard 2014, Northridge et al., 2011). They proved effective in disturbing bottlenose dolphin away from nets (Leeney et al., 2007). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015). Commercial activities such as a dredging have the potential to cause displacement of coastal bottlenose dolphin populations (Pirotta et al., 2013).
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes.
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland Cardigan Bay, Wales
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Certain activities require licensing. The coastal populations are targeted by research and are subject to long-term monitoring. The species has rarely been subjected to more invasive scientific studies (e.g. tagging) in the UK. Disturbance from research vessels is, however, a small component of all vessel traffic.	East Scotland Cardigan Bay, Wales
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with bottlenose dolphins (e.g. Hastie et al., 2003; Bejder et al., 2006; Meissner et al., 2015). Exposure to this pressure is limited both spatially and temporally, although it may be regionally significant when occurring e.g. for coastal populations (Lohrengel et al 2018). Boat presence is associated with a short-term reduction in foraging activity in bottlenose dolphins (New et al., 2013). Physical boat presence alone, as opposed to noise, is enough to cause short-term disruption (Pirotta et al., 2014) and impacts distribution and communication between bottlenose dolphins (La Manna et al., 2016. Heiler et al., 2016).	East Scotland Cardigan Bay, Wales South west England
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b).
	Change / removal of supporting habitat	Very little evidence of effects on bottlenose dolphin from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability, due to: competition with other marine predators, fishing or climate change, may have an impact. Starvation has been recorded as a cause of death in stranded individuals (see UK Strandings annual reports: http://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population. There is some recent information on prey preferences (Millian-Hernandez et al., 2015) but information on changes in prey is lacking. Lassalle et al (2012) noted that bottlenose dolphin may be more susceptible to a decline in food source due to the required prey biomass for their survival in comparison to other species.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Bottlenose dolphins are often attracted to vessels but monitoring of stranded animals shows that vessel strikes are not a typical cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure of small populations. Off Wales, the bottlenose dolphin population would potentially be at risk from collision with sub-surface marine renewable devices such as tidal turbines (Malinka et al, 2018) and these impacts may be locally significant.	Irish Sea
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	There are no records of bottlenose dolphin populations being impacted by oil spills in the UK. The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 was linked with unusual mortality events of bottlenose dolphins between 2010 and 2014 (Graham et al., 2017).
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Jepson et al., 1999, 2005; 2016; Hall et al, 2006; ICES, 2015b) with bottlenose dolphin exhibiting some of the highest levels ever recorded. Bottlenose dolphin was one of four species found to have PCB levels significantly higher than other species, which is linked with possible low reproductive capacity consistent with PCB-induced toxicity (Jepson et al, 2016).	East Scotland Cardigan Bay, Wales
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters.
	Entanglements in marine litter & ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Risso’s dolphin
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in the current monitoring scheme. Evidence from the strandings scheme suggest bycatch events of small cetaceans in creels and pots are very rare which suggests that individuals may be able to avoid them and therefore this activity is not considered a high risk. There have been reports of bycatch for this species through the stranding scheme (Deaville & Jepson, 2011), and a single record of a Risso’s dolphin bycaught in static nets through the UK bycatch observer programme (Northridge at al 2013).
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operations and/or different activities occur at the same time, or over an extended time period, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Stone and Tasker, 2006; ICES, 2012; Stone, 2015). However, it is not well understood what the impact of disturbance is on fecundity and survival of this species.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) to marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently placed ADDs associated with aquaculture shows they can affect movement patterns (this data is mainly related to harbour porpoise), local density and lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.	West Scotland
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). Pingers are currently used only on gillnet vessels >12m in length, which is a small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes.
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Cases of gas embolism have been identified in this species although it is unclear whether these were associated with particular noise events (Jepson, 2003; Jepson, 2004; Jepson et al., 2005; Deaville and Jepson, 2011). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters with certain activities requiring licensing. Scientific studies focus on photo ID and genetics. Disturbance from research vessels is a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). This species is not normally targeted but potentially some local disturbance as a consequence of activities targeting other species may occur.
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b). Potential for higher exposure to this pressure may be locally significant.
	Change / removal of supporting habitat	Very little evidence of effects on Risso’s dolphin from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability due to: competition with other marine predators, fishing or climate change, may have an impact on individuals. Starvation is a commonly recorded cause of death in stranded individuals (see UK Strandings annual reports: http://ukstrandings.org/csip-reports) but there is no understanding of its cause in the population.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical injury/mortality	Vessel strikes	Monitoring of stranded animals shows that vessel strikes are a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). There is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.	West Scotland Wales
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	There are no published records of any spills in which dolphin Risso’s dolphin were affected. Risso’s dolphin were observed swimming in oiled waters following the Deepwater Horizon oil spill (NEFCE/NOAA, 2015); however, it is noted that this does not exclude the possibility of short- or long-term health impacts.
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Risso's dolphins accumulate contaminants (Kim et al., 1996, Capelli et al., 2008). Cadmium, copper and zinc are found in high concentrations in squid, the preferred prey of Risso’s dolphin (Storelli et al., 1999; Blanco et al., 2006; Gaspari, 2004) indicating a potentially higher level of exposure than other species. Although metallothioneins plays an important role in controlling and detoxifying non-essential heavy metals in cetaceans (see Roesijadi, 1992), high levels can lead to renal failure and bone malformity in other species (Lavery et al., 2009). However, evidence for contaminant accumulation in the UK population is currently limited.
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. As squid are the preferred prey, the risk of plastic ingestion is potentially higher. No evidence of direct plastic ingestion has been recorded in UK waters but there has been in the Mediterranean (Bearzi et al., 2010).
	Entanglements in marine litter and ghost nets	Very little evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Long-finned pilot whale
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in the current monitoring scheme. Bycatch events of small cetaceans in creels and pots are very rare but there has been limited monitoring of these gears. However, given the predominately offshore distribution of this species and coastal nature of creeling and potting, we are confident that exposure is low and it is not considered a high risk to this species. Bycatch of long-finned pilot whales has been recorded in gillnets, purse seines and in trawl fisheries (Northridge, 1991; Reyes, 1991; Leeney et al., 2008; Northridge et al., 2017).
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operation and/or different activities occur at the same time, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (Stone and Tasker, 2006; Brownlow et al., 2011, 2014; ICES, 2012; Stone, 2015). However, it is not well understood what the impact of disturbance is on fecundity and survival of this species.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) to marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have investigated negative impacts from operational oil and gas platforms.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently placed ADDs associated with aquaculture shows they can affect movement patterns (this data is mainly related to harbour porpoise), local density and lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury. However, the offshore distribution of this species means they have limited exposure.
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed. The offshore distribution of the species will reduce exposure.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard 2014, Northridge et al., 2011). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet. The offshore distribution of this species means there is limited exposure.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015). Dredging and mining are generally a more inshore operation and therefore there is limited overlap with pilot whale distribution.
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes. However, the offshore distribution of this species means overlap with busy sea areas is low.
	Military activity and sonar	Behavioural impacts have been recorded (Rendell and Gordon, 1999; Antunes et al., 2014; Wensveen et al., 2015). Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). However, overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. The offshore nature of the pilot whale means it is not normally subject to more invasive scientific studies.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). Species is not normally targeted due to the offshore nature of its distribution.
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b) although unlikely to occur given the offshore nature of the species.
	Change / removal of supporting habitat	Very little evidence of effects on long-finned pilot whales from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability due to: competition with other marine predators, fishing or climate change, may have an impact. Starvation has not been recorded as a cause of death in stranded individuals.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Vessel strikes have not been recorded as a cause of death in long finned pilot whales in UK waters (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). However, there is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant. Exposure considered unlikely due to the offshore nature of the species.
	High energy, acoustic events, for example removal of unexploded ordnance/ explosions	Loud noise can result in injury to long finned pilot whales, particularly to their hearing (NOAA, 2018). In 2011, clearance of unexploded ordnance from a practice range was thought to have triggered a mass stranding event of long finned pilot whales (Brownlow et al., 2015).
Marine pollution	Oil pollution	There are no published records of any spills in which long-finned pilot whales were affected.
	Chemical pollution (e.g. CBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented. Levels of PCBs in long finned pilot whales are not as high as those recorded in other species in UK waters (Brownlow et al., 2011).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. As squid are the preferred prey, the risk of plastic ingestion is potentially higher. No evidence of direct plastic ingestion has been recorded for this species in UK waters.
	Entanglements in marine litter and ghost nets	No evidence of impacts in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Killer whale
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls. Limited monitoring of drift nets and none of creeling/pots in current monitoring scheme. Globally there are very few records of this species being bycaught although some cases of entanglement have been reported. It is unclear whether such entanglements are linked specifically to fishing activities. There has been a single case to date of a killer whale caught in a creel off the west coast of Scotland.
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operation and/or different activities occur at the same time, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (e.g. Stone and Tasker, 2006; Stone, 2015). It is not well understood what the impact of disturbance is on fecundity and survival of this species.
	Underwater explosions
	Pile driving
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) for marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have demonstrated such an impact.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently placed ADDs associated with aquaculture shows they affect movement patterns (this data is mainly related to harbour porpoise), local density and can lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury.
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. Evidence shows they can be effective for some species (e.g. Larsen et al., 2013, Larsen and Eigaard, 2014, Northridge et al., 2011). Pingers are currently used only on gillnet vessels >12m in length, which is a very small proportion of the UK gillnet fleet.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Vulnerability is highest in areas of busy shipping lanes. Background noise can interfere with communication between killer whales, possibly affecting activities such as cooperative foraging (Foote et al., 2004).
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Limited in UK waters, with certain activities requiring licensing. Population identification focuses on photo ID and biopsy work (e.g. Foote et al., 2010, 2011). Disturbance from research vessels is a small component of all vessel traffic.
Physical disturbance	Recreation and Wildlife tourism	There are multiple studies indicating behavioural impacts concerning tourist boat interaction with other species, e.g. bottlenose dolphin and common dolphin (e.g. Hastie et al., 2003; Neumann and Orams, 2006; Bejder et al., 2006; Stockin et al., 2008; Meissner et al., 2015). Species is targeted in the regions in which they occur, this can have implications for conservation (Jelinski et al., 2002).
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b). Potential for higher exposure to this pressure in West Scotland.	West of Scotland
	Change / removal of supporting habitat	Very little evidence of effects on killer whale from changes to or removal of supporting habitat, but may be locally significant.
	Reduction in availability of prey	Changes in prey availability, due to competition with other marine predators, fishing or climate change, may have an impact. Although based on limited data, starvation has been recorded as a cause of death in stranded individuals (Deaville and Jepson, 2011), but there is no understanding of cause in the population.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Monitoring of stranded animals shows that vessel strikes are a cause of death for this species, although there have been very few post mortems (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b). There is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to cetaceans, particularly to their hearing (NOAA, 2018).
Marine pollution	Oil pollution	Although evidence is limited, oil spills have resulted in increased death rates for killer whales out with UK waters (Matkin et al., 2008).
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented with killer whales having the highest recorded exposure to contaminants such as PCBs (Ross 2000; McHugh et al., 2007; Wolkers et al., 2007; Law et al., 2012; Jepson et al., 2016).
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters although there have been few post mortem investigations.
	Entanglements in marine litter and ghost nets	Single case of entanglement in UK waters from strandings data (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b).
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to individuals (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

Minke whale
Pressures and activities		Evidence supporting the assessment	Regional variations where vulnerability likely higher than UK assessment
Removal of non-target species (i.e. bycatch or entanglement)	Creeling and potting	Monitoring of bycatch (Northridge et al., 2016) has focused on set nets and until recently, pelagic trawls, and minke whales have not been reported as captured in these gear types. Limited monitoring of drift nets and none of creeling/pots in current at-sea bycatch monitoring scheme. However, available information in strandings and reported records suggest that minke whale deaths due to entanglement in fishing gear, principally in creel lines, represent the single most frequently documented cause of anthropogenic mortality in Scottish and UK waters (Northridge et al, 2010; Pierce et al., 2004; Deaville and Jepson, 2011).	West Scotland
	Drift net fishing
	Trawling and purse seining
	Set (fixed) net fishing
Acoustic disturbance	Cumulative impacts of acoustic disturbance	Sound introduced in the marine environment by human activities is one of the key areas of concern with regards to potential detrimental effects. Whilst the vulnerability to a particular activity may be low, when multiple operation and/or different activities occur at the same time, the impact is likely to be greater.
	Seismic or geophysical surveys	Disturbance is a documented response of cetaceans to noise (e.g. Stone and Tasker, 2006; Stone, 2015). Minke whales showed strong behavioural responses to a large, active airgun array in UK waters (Stone, 2015; Stone et al. 2017). Repeated exposure to noise generating activities may therefore have the potential to cause longer term impacts on minke whale populations, although it is not well understood what the impact of disturbance is on fecundity and survival of this species. Minke whales are likely to be sensitive to lower frequency noise (Nowacheck et al. 2007). Behavioural disturbance of minke whales from pile driving may be expected up to 40km from the source (Bailey et al. 2010). At the UK scale, exposure of minke whales to pile driving is low although it may be regionally significant in some areas/seasons.	North Sea
	Underwater explosions
	Pile driving		North Sea
	Operational offshore wind farms	Noise from operational wind farms is produced at frequencies that are not thought to be a significant concern (Marmo et al., 2013) for marine mammals.
	Operational oil and gas platforms	Whilst the impact of drilling is potentially high (Boyd, 2008), there have been no studies that have demonstrated such an impact.
	Acoustic deterrent devices (ADDs)	Evidence for the effect of permanently placed ADDs associated with aquaculture shows they affect movement patterns (this data is mainly related to harbour porpoise), local density and can lead to habitat exclusion (ICES, 2015b). ADDs are also used as mitigation prior to offshore construction and for ordnance detonation; they are used to exclude animals from the area as a means of mitigating against injury. A study on the effects on minke whales, in Iceland, was investigated through controlled exposure experiments of tagged animals. Both speed and the directness of their path increased in relation to exposure to the ADD signal (McGarry et al. 2017). Whilst at the UK scale, exposure is low, it may be regionally/locally significant during summer when minke whale density is greatest around the UK.	West Scotland North Sea
	Fish finders and depth sounders	Fish finders and depth sounders occur on almost all vessels but the noise produced at these frequencies, although audible, are not a significant concern (Deng et al., 2014). However, new devices are being introduced and the sensitivity to such and potential impacts should be regularly reviewed.
	Pingers	Pingers are used to alert animals to the presence of nets to reduce bycatch risk. There is no evidence in the UK as to their impact on minke whales; however, given the limited of use of pingers in the UK gillnet fleet, confidence in low exposure is high.
	Mining and dredging activities	Noise emitted during dredging operations is broadband and is unlikely to cause damage to marine mammal auditory systems, but masking and behavioural changes are possible (Tillin et al., 2011; Todd et al., 2015).
	Vessel noise	Disturbance reactions have been observed in response to shipping (Richardson, 1995). Noise from shipping vessels is thought to affect baleen whales in particular, due to their good hearing at low frequencies (Götz et al., 2009). Increased vessel traffic from marine construction activities was correlated with a decrease in minke whale presence off the northwest coast of Ireland, suggesting they were displaced by the high levels of vessels presence (Anderwald et al., 2013). Vulnerability is highest in areas of busy shipping lanes.	North Sea
	Military activity and sonar	Activities are likely to cause behavioural responses such as disturbance, which are energetically costly but whether these lead to long-term population level impacts is poorly understood (Harris et al. 2017). Responses vary between and within individuals and populations (Harris et al. 2017). Studies out with the UK of tagged minke whales, showed strong avoidance behaviour in response to naval sonar (Sivle et al. 2015; Kvadsheim et al., 2017). Overall low vulnerability across the UK but regionally high at certain times when operations are occurring.	West of Scotland
Physical disturbance	Scientific studies (e.g. tagging, photo ID, biopsy)	Focussed on two main areas of their UK distribution in Moray Firth (e.g. Robinson et al. 2009) and west of Scotland (e.g. Macleod et al. 2004). Disturbance from research vessels is a small component of all vessel traffic and exposure in relation to their range is relatively low.
Physical disturbance	Recreation and Wildlife tourism	Reported impacts of whale watching vessels on minke whales include avoidance and disruption of feeding (Christiansen et al. 2013; Christiansen and Lusseau, 2015). However, Christiansen and Lusseau (2015) reported that cumulative exposure to whale watching vessels had no impact on female reproductive success. At the UK scale, exposure is low although may be locally significant where targeted tourism occurs.	West Scotland
Change to habitat	Barrier to movement	Evidence of barrier to movement is very limited but may be locally significant (ICES, 2015b). Potential for higher exposure to this pressure in West Scotland.	West of Scotland
	Change / removal of supporting habitat	No evidence of changes to or removal of supporting habitat.
	Reduction in availability of prey	Changes in prey availability, due to competition with other marine predators, fishing or climate change, may have an impact. Although based on limited data, starvation has been recorded as a cause of death in stranded individuals (Deaville and Jepson, 2011); 11% of all minke whales examined post-mortem between 2000 and 2017 reported to have died due to starvation (CSIP annual reports, http://ukstrandings.org/csip-reports). There is no understanding of the cause of this in the population.
	Localised temperature changes	Local water temperature changes from, for example, cooling water discharges from power stations, is unlikely to have population level effects due to its localised nature.
Physical Injury/mortality	Vessel strikes	Monitoring of stranded animals shows that vessel strikes are a cause of death for this species (Deaville and Jepson 2011; Deaville, 2016; ICES, 2015b); 7% of minke whales necropsied by CSIP between 2000-2017 had a cause of death of physical trauma due to the ship strike (CSIP annual reports, http://ukstrandings.org/csip-reports). There is no requirement for vessels to report strikes occurring at sea, and carcasses may not wash up on land.
	Collision with renewable energy devices	Few wet renewable devices in place, limited efforts to measure impacts and thus little understanding or evidence of impact. Where such projects are implemented, vulnerability will be higher due to increased exposure. Potentially locally significant.
	High energy, acoustic events, for example removal of unexploded ordnance.	Loud noise can result in injury to minke whales, particularly to their hearing (NOAA, 2018). At the UK scale, exposure is low compared to the range of this species.
Marine pollution	Oil pollution	There is no evidence within the UK on the impacts of oil on minke whales; however, exposure is low.
	Chemical pollution (e.g. PCBs, butyltins, PAHs, Radionuclides, heavy metals)	Impact of contaminants on cetaceans is well documented (Ross 2000; McHugh et al., 2007; Wolkers et al., 2007; Law et al., 2012; Jepson et al., 2016). However, whilst evidence of persistent organic pollutants (POPs) has been found in minke whales in the northeast Atlantic (Kleivance and Skaare, 1998; Rotander, Kärrman, et al., 2012; Rotander, van Bavel, et al., 2012), there is minimal information on how pollutants currently affect minke whales in UK waters.
	Plastic pollution (ingestion)	Plastic ingestion is monitored through post-mortem examination of stranded animals. No evidence of direct plastic ingestion has been recorded for this species in UK waters but there are records elsewhere (e.g. Normandy coast - de Pierrepont et al. 2003)
	Entanglements in marine litter and ghost nets	Entanglements of this species occur, but it is not always possible to determine whether it ghost gear or fixed gear that has caused the mortality.
	Eutrophication, sewage pathogens	Nutrient enrichment in areas of agriculture, aquaculture or sewage may pose a threat to cetaceans (Simeone et al., 2015), but the consequence of exposure to the population is unlikely to be a concern.

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Information

Section 5 – Confidence Scores and Supporting Evidence

Confidence

Evidence

Assessing confidence

Confidence Decision Tree

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