Scottish Marine Protected Areas (MPA) monitoring strategy: supporting annexes 1 to 6

Annex 4: Monitoring methods - considered by feature groups

Mobile Species

This annex provides a summary of monitoring methods used for the different feature groups and provides links to further detailed information.

Marine Mammals

Seals

The methods used for monitoring harbour and grey seals in Scotland are routinely set out in the annexes to the annual SCOS (Special Committee on Seals) advice provided to government on matters related to the management of UK seal populations. The annual SCOS reports are available online^[43].

The Sea Mammal Research Unit (SMRU) provide a summary of annual seal monitoring through the SNH commissioned report series^[44]. SMRU are leading the development of the UK monitoring options for seals.

Cetaceans

Hammond et al. (2013) describe the aerial and shipboard survey methodologies used in the decadal, broad scale SCANS (Small Cetaceans in the European Atlantic and North Sea) surveys, undertaken to estimate the population abundance of the most common cetaceans (including bottlenose dolphins, harbour porpoise and minke whales). However, this large scale survey is a snapshot and cannot provide details on inter-annual variation, distribution or seasonal use

An overview of the different sampling methodologies relevant to cetaceans (and basking sharks) is provided in MacLeod et al. (2011). All future MPA-related cetacean studies should contribute to the Joint Cetacean Protocol (JCP) or subsequent collaborative data collation programme^[45]. A combination of all methods may be needed to meet MPA monitoring and reporting obligations.

Bottlenose dolphins

Large scale surveys such as SCANS provide information about the overall abundance and distribution of bottlenose dolphins throughout their range. Additional focused methods are used for collecting data on individual movements and survival to understand how bottlenose dolphins are using the area. Details of the photo-ID survey protocols and associated mark-recapture analyses used in the Moray Firth SAC to monitor the status of the bottlenose dolphin population are set out in Cheney et al., (2014). Similar methods are used in the Tay by St Andrews University. The SAC monitoring is of sufficient resolution to detect trends in abundance and allow population demographics to be studied. The 2014 report also presents summary information on the role and design of passive acoustic monitoring (C-PODs) undertaken to enable a more detailed assessment of patterns of usage of the SAC. The current Moray Firth SAC monitoring programme was devised following a detailed review of different options as presented in Thompson et al. (2004).

Marine birds

Seabirds

Breeding populations on land - The SMP uses agreed methods as set out in the SMP Handbook^[46]. This applies solely to breeding distribution, abundance, survival and productivity.

Non-breeding seabirds - Seabird population distributions at sea in the UK have been monitored previously under the ESAS. Agreed ESAS standards and protocols^[47] typically involved bespoke surveys undertaken from suitable vessels. JNCC are currently assessing whether information could be collected using volunteers and a network of Vessels of Opportunity (VoO).

Marine waterbirds

Breeding populations - Surveys vary in the geographical coverage, though most focus on protected areas (especially SPAs and SSSIs). Methods vary between species and cannot be generalised, though most require a sampling regime (e.g. red and black-throated diver), often suitably stratified. Some surveys are carried out on the whole population (e.g. common scoter).

Non-breeding populations - WeBS surveys are volunteer based counts, usually (but not always) undertaken on a monthly basis. Details of the methods used for the Core Counts^[48] and the Low Tide Counts^[49] are available online via the BTO website^[50].

NEWS surveys^[51] are volunteer based counts, undertaken roughly every decade.

Surveys can either be undertaken by boat using ESAS-type survey methods, or using aerial surveys as carried by JNCC for SPA identification. Light aircraft can survey large and inaccessible areas in a short space of time. This reduces the risk of double counting and can sometimes be more cost effective than boat surveys. A line-transect sampling method is used which allows the use of distance sampling^[52] to calculate more accurate population estimates. The sampling method allows bird distribution data to be collected at a very fine spatial scale. The line-transect method used by the JNCC Seabirds at Sea Team, and a full description of the methods used can be found in Dean et al. (2003)^[53]. It should be noted that digital aerial survey methods have now largely superseded visual aerial survey methods, and there is evidence that the two methods can differ in their results (Buckland et al., 2012).

Fish

A range of survey methods can be utilised to monitor and study fishes within and outside MPAs. Two main types of survey method are available. Which is most appropriate will depend on the objectives of the study, reporting obligations and the particular environmental circumstances and conservation objectives.

1) Methods for collecting data on species diversity, abundance and distribution.

If the MPA is large and covers a range of environmental conditions (e.g. depths) and habitats then some form of fish capture methods are generally required. In some areas, trawling will yield the most representative sampling of fish. Good trawl data will give excellent information on species diversity, abundance and distribution. However trawling can be destructive and would not be appropriate for areas of high seabed sensitivity. Trawling is also not possible in some areas, e.g. very steep slopes or rock reef habitats. In such cases alternatives methods are required. These may include baited traps and cameras which will give estimates of those species attracted to bait (generally scavenger species). Fish traps are generally preferable as they provide reliable species identification and the same individuals are not repeatedly sampled which can be a problem with baited camera systems. Fish traps do however have the draw back that large species can consume smaller species within the trap and are restricted to relatively shallow areas. A less selective method that can be used is a towed camera system that will be unbiased with respect to species feeding habits. Towed camera systems can cover large areas, but can have problems with identification of species, most notably small species. Towed camera systems can be used to survey areas where trawl surveys are not possible or desirable (McIntyre et al., 2014) and do not cause adverse impact to the seabed. They can also be useful for identifying essential fish habitat, for example juvenile areas or areas where egg cases are deposited. Diver surveys (visual recording) of species can be effective in some situations, but have limitations of depth and sampled area.

Each of these methods carried out in a systematic way and over a suitably long time period can provide indices to monitor change in fish diversity and abundance. They are each subject to their own sampling caveats. Often a combination of methods is required to cover all areas within a site.

2) Methods for collecting data on individual movements and survival.

A range of tagging methods is available to study individual movements. Depending of the level of sophistication and expense these range from conventional ‘flag’ tags to electronic satellite tags. Simple flag tags can provide estimates of movement and survival if catch and release is done in a systematic way (repeat sampling) and is carried out on a large number (> 100) of individuals over a long period of time (at least 6 sampling periods). PIT (passive integrated transponder) tags are a slightly more expensive, but more reliable way to infer survival probabilities than conventional tags. Electronic tags can provide much more detailed information of space use between release and recapture and give insight into habitat preferences, e.g. depth. Depending on the species and its range of movements different tags are preferable. For resident species, acoustic tracking with individually coded transmitters is the best option for defining home ranges and movements. If the species is more wide ranging and likely to move out of the study area then data storage tags or satellite tags provide a better option. However, these more sophisticated tags are very costly.

Common skate

A combination of all methods described above may be needed to meet MPA monitoring and reporting obligations. For example, recent work on common skate has relied upon trawl data to generate initial, broad-scale distribution maps. Within the Loch Sunart to the Sound of Jura MPA, finer resolution conventional flag tag and PIT tag studies have then been used to infer survival rates, with electronic tracking (acoustic and data storage tags) undertaken to explore habitat usage and home ranges (Neat et al., 2014, Pinto et al., 2016).

Photo-identification techniques (photo-ID) recently applied to manta rays (e.g. Marshall et al. 2009; Marshall et al. 2011) are also being explored to aid individual common skate identification and inform population dynamic studies (see also Annex 6).

Sandeels

There are no plans to monitor sandeels at inshore grounds. MSS have a long survey time series for the Mousa to Boddam MPA area prior to 2008. Any monitoring would only inform on environmentally driven changes in sandeel numbers.

MSS monitor the Turbot Bank MPA, where there can be a directed fishery, as part of a winter dredge survey of sandeel assessment area 4. Given the dynamic nature of sandeel habitat this is not monitored. There is no MSS monitoring of NW Orkney MPA as that is not fished. There have been occasional larval surveys - the last in 1994 and the area is partly covered by the Continuous Plankton Recorder (CPR) survey^[54].

Seabed habitats and species

Details of methods applied in previous CSM work undertaken in nearshore MPAs is provided in relevant site or method specific reports published on the SNH website^[55].

Noble-James et al., (in prep.) introduces a stepwise framework by which to plan and design a benthic habitat monitoring programme, from setting objectives to statistical analysis. Each section provides background information and guidance on best practice for each stage of the design process, with specific guidance for Type 1, 2 and 3 monitoring where appropriate.

Large-scale features

Five large-scale features of potential wider significance to the overall health and biodiversity of Scotland’s seas were included in the development of the MPA network. These features are seamounts; continental slope; shelf deeps; shelf banks and mounds; and fronts^[56].

Specific examples of each of these features are now incorporated within the existing site series in locations where evidence was available to suggest that they contribute to ecosystem function, for instance in terms of playing a key supporting role within the site or in supporting linkages within the network and across the wider seas.

In light of the significant scale, envisaged role and generally robust nature of the large-scale features themselves, future monitoring effort is directed at the habitats and species they support. For many of the examples currently represented within the network this entails work on specified benthic habitats mainly identified as protected features of the site in their own right (e.g. the fan mussel aggregation and burrowed mud protected features situated within the shelf deep at the heart of the Small Isles MPA).

Further consideration will be given on a site-by-site basis to the relative merits of monitoring persistent aggregations of mobile species if they are associated with the large-scale feature, for example due to the influence of local topography on hydrographic conditions and elevated productivity^[57].

Pressure Monitoring

Mobile species

Strandings

Investigation of the major causes of death in marine mammals (cetaceans and seals) and basking sharks is monitored through the Scottish Marine Animal Strandings Scheme (SMASS^[58]) and the UK Cetacean Strandings Investigation Programme (UK CSIP)^[59] through targeted necropsy examinations and ad hoc biopsy sampling. The programmes are sufficient for determining and detecting changes in the relative causes of death for the most commonly stranded species, as well as providing an effective route for identifying any substantial new threats through surveillance on the incidence of disease.

Bycatch

The UK Bycatch Monitoring Scheme^[60] undertakes observations of incidental cetacean bycatch by commercial fishing vessels in relation to EU Regulation 812/2004 and the Habitats Directive. The scheme is currently operated by SMRU and focuses on certain gears, areas and species with known bycatch or risk of bycatch.

Seabed abrasion and other pressures from fisheries activity

Abrasion pressure on the sea bed from demersal fishing gear is one of the primary pressures identified for sea bed habitats and needs to be inferred from data collected on the activity of the relevant fishing fleets. This is achieved using position data collected from vessel monitoring systems (VMS) required to be fitted to all registered fishing vessels operating in UK waters over 12 m in length (overall). These data are centrally collated by the Marine Management Organisation and Marine Scotland and can be used to infer vessel tracks and trawling activity using likely towing speed as a proxy. Individual “pings” of vessel location are transmitted every 2 hours, meaning that vessel tracks need to be inferred and that changes in direction by vessels can result in activity away from inferred tracks.

Monitoring of activity can be utilised in 2 ways:

a) ad hoc site specific analysis of “ping” data to infer the potential historic and current level of fishing activity relevant to a protected area. This can be used to consider for example prioritisation of monitoring effort and may be used to inform changes to management measures relevant to a feature or a site.

b) The development of a derived “pressure layer” for seabed abrasion which can be collated periodically (e.g., annually) and provides a quantified estimate of the abrasion experienced by a specific area of sea bed. Such an approach is being used as part of the process to assess whether sea bed integrity (Descriptor 6) is at “Good Environmental Status” for the Marine Strategy Framework Directive. This process involves combining the VMS data from appropriate portions of the fishing fleet where contact with the seabed is likely during trawling and calculation of indices of abrasion such as the “swept area ratio” (Church et al., 2015). The outputs are gridded at high resolution and can be used to provide an indication of any spatial or temporal changes to abrasion pressure (or other pressures directly relating to activity of portions of the fishing fleet) relative to protected areas or features.

Unfortunately, these data miss those vessels that have an overall length less than 12 m which also engage in fishing practices that result in abrasion of the seabed. Although the majority of vessels in this size class operate static gear with much lower pressure on sea bed habitats, different data would need to be used to monitor these pressures. “ScotMap” was an attempt to map the activity, value and spatial usage of the non-VMS fishing fleet in Scottish inshore waters and provides some data, but as no data on effort were collected it is not possible to directly or quantitatively derive pressure from the data set. The data were also collected as a snapshot in 2011 and is not planned to be repeated (Kafas et al., 2017)^[61].

Various efforts are underway to roll out new technologies for the recording of vessel position for inshore small vessels (<12 m) including the roll out of AIS (automatic identification system), allowing the future recording of position, tracks and speed from this previously unrecorded portion of the Scottish fleet. Such data together with information on the gear being used will allow improved monitoring of pressures from fishing activities on MPAs and PMFs.

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