Crab and lobster fisheries - stock assessments: results 2016 to 2019

3. Results and Discussion by Species

3.1 Brown Crab

3.1.1. The Fishery

The brown crab fishery is long established and landings, although variable, have increased significantly over the last 40 years (Figure 2 a). Reported landings averaged around 2,000 tonnes in the late 1970s, increased to a maximum of about 12,000 tonnes in 2007 and fluctuated between 11,000 tonnes and 12,000 tonnes until 2015. In recent years, landings of brown crab into Scotland have decreased to around 7,000 tonnes. In 2020, a reduction of over 30% was recorded in relation to 2019. It is difficult to establish how accurate the pre 2006 data are, as landings are thought to have been under-recorded before the introduction of the UK ‘buyers and sellers’ legislation. The value of landings has increased in line with the tonnage landed. However, the price per kilogram changed little until the recent ~5 years when there has been a significant increase. (Figure 2 b and Figure 2 c). One kilogram of brown crab was sold for an average of £2 at first sale during the period 2016 to 2020, up from the average of £1.3 seen in the period 2013-2015.

The annual brown crab landings by assessment area are shown in Figure 3. The principal fishing areas for brown crab in Scotland are the Hebrides, Orkney, East Coast and South Minch; landings from these areas accounted for over 60% of the total in recent years (Table 8). Landings from the offshore areas of Sule and Papa increased sharply in the 1990s when the fishery expanded, but seem to have decreased in both areas during the last 5-10 years. Substantial declines in landings in recent years are also apparent in the Hebrides, North Coast and Orkney assessment areas. Landings from both the East Coast and South East have shown an increasing trend since the early 2000’s. The spatial distribution of brown crab landings by ICES statistical rectangle (including Irish landings) from 2016 to 2020 is shown in Figure 6. There were no major changes in relation to the most important rectangles for brown crab landings, compared to the previous assessments. Landings by non-UK vessels taken from the Scottish assessment areas were relatively low (mostly by Irish vessels) and usually confined to the South Minch (rectangle 40E3). The Irish fishery in Scottish waters has contracted in recent years with previously fished grounds in the Hebrides, Sule and North Coast not currently fished by Irish vessels. There is an important fishery for brown crab on the Malin shelf (Irish assessment area) that is exploited by Irish vessels, with most landings being taken from the Donegal region (rectangles 40E2, 39E2 and 39E1). There were no other regions of importance for brown crab landings around Scotland outside the Scottish assessment areas.

3.1.2. Sampling Levels

The number of sampled brown crabs, number of trips and percentage of sampled fishing trips are shown in Table 3. Good sampling coverage was achieved for the most important (in terms of landings) assessment areas, with samples being obtained throughout the year in the period 2016-19. A decline in the number of sampling trips was noted in North Coast with no samples collected in 2018, before sampling again in 2019 although at a low level. The percentage of trips sampled was generally less than 3% in assessment areas where daily inshore trips are common. In the Orkney (where OSF has been sharing considerable amounts of data with MSS) and Papa assessment areas, which include offshore grounds, sampling percentages were higher (Table 3) as the fishery is dominated by larger vessels, which tend to make fewer but longer trips. Sampling data from Ullapool (which was not included in the previous round of assessments) for 2016-19 was sufficient to conduct an assessment. Sampling data were considered to be insufficient (low numbers and infrequent sampling) to conduct an assessment in the Mallaig area (Annex A). Amongst the assessed areas, the South Minch, East Coast, South East and the Ullapool areas had the lowest sampling levels with less than 1% of fishing trips sampled in the period 2016-19. However, data included samples from all quarters and the averaged length frequency (Annex B) were similar to those in other adjacent areas and therefore assumed to be representative, despite the low sampling levels.

3.1.3. Size-based Indicators and Sex Ratio

Size-based indicators of brown crab in the landings from each assessment area are shown for males in Figure 9 and for females in Figure 10. The data are typically noisy. In recent years (2016-19), the mean size of males was above the respective reference point in the Hebrides and Papa (Table 11). For females, the mean size was above the reference point in Hebrides, Orkney, Papa and Sule. In several areas, the mean size in the landings appears to have increased (both sexes), which is driven mainly by an increase in size at first capture following the implementation of a MLS in 1998. The MLS for brown crab increased again in 2017 from 140 mm to 150 mm in all areas except Shetland (The Specified Crustaceans Order, 2017) but any potential effect of this change is not visible in any of the size based indicators. In 2016-19, the mean sizes of the largest 5% of males and females were above the reference point in Papa (Table 11). For males, the mean sizes for the largest 5% was also above the reference point in the Hebrides. There is some evidence of a positive trend in the mean size of the largest individuals throughout the time series in Shetland and the Clyde. In Shetland, the mean size of the largest females was close to the reference point in 2018. In all areas, the size at first capture of males was well above the size at first maturity L_mat throughout the time series. For females, in recent years size at first capture was above size at first maturity. In the SE, SH, EC and CL the size at first capture was fluctuating around L_mat prior to the year 2000.

The sex ratio in landings of brown crab varied greatly between assessment areas but in most cases shows no trend over time (Figure 15). Consistently higher percentages of females in landings over the time series are evident in areas, which include offshore fishing grounds such as the Hebrides (70%), Papa (90%), Sule (90%) and North Coast (90%). The only inshore area with a clear predominance of females in landings is the South Minch (55%). The South East is a male dominated fishery (70% males). Orkney has shown a decrease in the male percentage in landings from over 70% in the 1980s to around 40% in recent years, whereas the sex ratio in Shetland and East Coast displayed the opposite trend.

3.1.4. Survey Data Analysis

3.1.4.1. East Coast

The spatial distribution of brown crabs in the East Coast indicated that catch rates for both sexes and all sizes in the dredge survey were higher in coastal areas particularly in the Moray Firth and the Firth of Forth (Figure 21). Towards the south east coast areas of the Tay and the Firth of Forth, high catch rates were also predicted further offshore. Trawl survey catch rates were similar in distribution to the dredge surveys, however, trawl surveys did identify a region of medium density catch rates in Orkney. Male and female brown crabs were similarly distributed in the dredge survey data with juveniles of <100mm CW showing an inshore distribution.

An abundance index for East Coast brown crabs was derived from the dredge model and compared to the index from the trawl model. The abundance index estimated from the dredge model increased gradually from 2008 and peaked in 2015 followed by a decline up to 2019 (Figure 24 a). The trawl catch rate for the same period followed a similar pattern with an increasing trend until 2017 and a subsequent decline.

The GAMs used to derive the recruitment index showed that recruitment was found to be dependent on year, distance to coast and geographical position which were all significant (p<0.05) (Mesquita et al., 2021). The recruitment index shows an increase in the catch rate of juvenile crabs until reaching a peak in 2014. This is then followed by a decline in recruitment until 2019 (Figure 25 a).

The mean length distributions of crabs captured in the East coast surveys are shown in Figure 26. The dredge survey (median=135 mm, mean=136.6 mm) captured generally smaller crabs than the trawl survey (median=162 mm, mean=158.5 mm). The median size per year (for those years where both dredge and trawl surveys were available: 2008-2019) was found to be significantly correlated (Pearson correlation=0.84, p<0.001) in the two surveys but fluctuated with no trend throughout the study period.

3.1.4.2. West Coast

Spatial distribution in the West Coast showed that catch rates in the dredge survey were higher in inshore areas (Figure 22). Male brown crabs had the highest catch rates close into shore particularly in the area of Mull, the Small Isles and around the south east of Barra. Female distribution was more widespread, with moderate to high density catch rates throughout the full dredge survey area in the West Coast. Juveniles showed an inshore distribution similar to that of males. Trawl survey data indicated a consistent moderate density catch rate throughout the whole West Coast, however the trawl survey covers a larger area with lower station density than the dredge survey.

The abundance index estimated for the west coast dredge survey increased gradually from 2008 to 2016 and declined in recent years. The abundance index derived from the trawl survey data is only available since 2011 and shows a fluctuating trend until 2014 and a decline in the last six years (Figure 24 b).

The estimated recruitment index for the West Coast displays a steady trend between 2008 and 2013. Recruitment then rose to a peak in 2015 at near 30 crabs per km² before declining in recent years to just below 10 crabs per km² in 2019 (Figure 25 b).

The mean length distributions of crabs captured in the west coast surveys are shown in Figure 27. The dredge survey (median=127 mm, mean=130 mm) captured generally smaller crabs than the trawl survey (median=170 mm, mean=165.3 mm). The mean size of crabs captured in the west coast was lower than that on the east coast for the dredge survey, however, an opposite trend was found when comparing the mean size of crabs caught in the trawl survey. The median size per year (for those years where both dredge and trawl surveys were available: 2011-2019) was found to be significantly correlated (Pearson correlation=0.74, p=0.02) in the two surveys but fluctuated with no trend throughout the study period.

3.1.4.3. Shetland

Despite the limited spatial coverage of the data (dredge only), there was still a clear propensity for higher catch rates of brown crabs in the most inshore waters around Shetland (Figure 23). Higher catch rates were observed around Yell and Unst and to the southern point of the mainland off Sumburgh. Despite some missing data between 2012 and 2015, the Shetland abundance index appears lower in the most recent 5 years than in 2011 and 2013. (Figure 24 c).

A trawl abundance index was not calculated for Shetland given the low number of trawl stations available close to Shetland. Additionally, a recruitment index was not derived for Shetland due to the very low catch rates of juveniles in the dredge survey.

The mean length distributions of crabs captured in the Shetland surveys are shown in Figure 28. The median size of crabs caught in the dredge survey was 120 mm and the mean size was 120.3 mm. There were very few animals caught in the trawl surveys around Shetland (typically less than three animals, except in 2011, 2012 and 2020) which explains the missing length data in Figure 28. The median and mean size per year in the dredge survey fluctuated with no trend throughout the study period.

3.1.5. Length Cohort Analysis

Results of assessments based on LCAs and per recruit analysis, summarising estimates of fishing mortality in relation to F_MSY, are shown below. Estimated fishing mortalities in relation to previous assessments are presented in Figure 29 (males) and Figure 30 (females). Brown crab biomass and yield-per-recruit plots for each assessment area are shown in Figure 35 (males) and Figure 36 (females).

Brown crab stock status, relationship between F and F_MSY for 2006-08, 2009-12, 2013-15 and 2016-2019.

Assessment period		F (Fishing Mortality)
		2006- 2008	2009- 2012	2013-2015	2016-19
Clyde	Males	no	unknown	no	no	Above FMSY
	Females	no	unknown	no	between	At FMSY
Hebrides	Males	no	ok	between	no	Above FMSY
	Females	no	no	no	no	Above FMSY
North Coast	Males	no	ok	no	no	Above FMSY
	Females	no	ok	no	no	Above FMSY
Papa	Males	unkown	ok	ok	ok	Below FMSY
	Females	unkown	ok	between	ok	Below FMSY
Shetland	Males	unknown	unknown	no	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Sule	Males	no	between	no	no	Above FMSY
	Females	between	no	no	no	Above FMSY
East Coast	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
Mallaig	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Orkney	Males	no	no	no	no	Above FMSY
	Females	no	no	no	between	At FMSY
South East	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
South Minch	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
Ullapool	Males	unknown	unknown	unknown	no	Above FMSY
	Females	unknown	unknown	unknown	between	At FMSY

In the most recent assessments, nine of the eleven assessed areas were fished above F_MSY to some extent (Table 14). Fishing mortality for both males and females was estimated to be above F_MSY in the East Coast, Hebrides, North Coast, South East, South Minch and Sule. In the Clyde, Orkney and Ullapool, fishing mortality for females was at F_MSY while males were fished above F_MSY. In Papa, recent fishing mortality was below F_MSY. Fishing mortality assessment results for Shetland were deemed inconclusive for both males and females due to contradictory results obtained when using the two alternate sets of biological parameters (see section below and discussion). No assessments were performed for the Mallaig area as the sampling data collected were considered insufficient to run LCAs.

3.1.6. Comparison with Previous Assessments

The current assessment uses a fixed length range to calculate an average fishing mortality and can be compared with previous assessments which used the same range (Mesquita et al., 2011; Mesquita et al., 2016; Mesquita et al., 2017; Mill et al., 2009). Estimated F has decreased in relation to the last assessment in all areas except for females in the East Coast. (Figure 29 and Figure 30). The main changes in status in relation to F_MSY are evident in the Clyde and Orkney females, which were both above F_MSY and are now fished at F_MSY while males in Hebrides were previously at F_MSY and are now fished above F_MSY.

Estimates of F for Shetland (using Shetland parameters) are higher than those estimated elsewhere (Table 14, Figure 29 and Figure 30). This is due to the use of different growth rate (K) and natural mortality (M) parameters specific to Shetland (Table 6). To examine what underlies these differences, LCAs were run for all areas using both the Shetland and the rest of Scotland biological parameters and results compared (Annex C). Shetland’s high natural mortality rate results in flat-topped YPR curves with both higher estimates of current F and F_MAX (the F_MSY proxy) compared with other areas, particularly for female brown crab (Figure 30 and Table 14). This is further discussed in section 4.3.

3.2 Velvet Crab

3.2.1. The Fishery

Velvet crab landings increased gradually until the mid-1990s followed by a slight decline up to 2005 and a sharp increase in 2006. It is not clear, however, whether this increase in landings reflects the introduction of the UK ‘buyers and sellers’ legislation or an expansion of the fishery at this time. In recent years, landings have decreased and were around 1,600 tonnes in 2020. The value per unit weight of velvet crab remains higher than that of brown crab and is currently approximately £2.5 per kilogram (Figure 2 b). The three areas that have historically had significant velvet crab fisheries are the Hebrides, Orkney and South Minch, although the fisheries in the two latter areas have shown a marked decrease over the last ten years (Figure 4). Landings in the East Coast increased sharply in 2005 and have been fluctuating ever since but this area remains one of the more important areas for the velvet crab fishery. These four areas accounted for about 80% of velvet crab landings in Scotland in the period 2016-19 (Table 9). Figure 7 shows the spatial distribution of velvet crab landings 2016-19. Most landings were taken from inshore areas; only very small amounts were reported from offshore grounds in Papa and Sule. There were small landings of velvet crab from around Scotland reported from outside the assessment areas including north of the Hebrides and in ICES rectangles 44E9 and 45E8 in 2017.

3.2.2. Sampling Levels

The numbers of sampled velvet crabs, number of trips and percentage of sampled fishing trips are shown in Table 4. The percentage of trips sampled was generally lower than that achieved for other species. In the Clyde, Hebrides and Orkney, temporal coverage was good with samples generally being obtained throughout the year in the period 2016-19. The South Minch is one of the important areas for the velvet crab fishery where the number of samples has been relatively low in the past, although this improved in 2016-19 compared to 2013-15 (Mesquita et al., 2017). Assessments were conducted for the Clyde, Hebrides, Orkney, South Minch, East Coast and South East. Sampling data were considered to be insufficient (low numbers and infrequent sampling) to conduct assessments in the Mallaig and Ullapool areas (Annex A) while there is no fishery for velvet crabs in the offshore areas of Papa, Sule and North Coast. An LCA analysis was attempted for the Shetland area but the results were not conclusive (see section 4.2).

3.2.3. Size indicators and Sex Ratio

Size-based indicators for velvet crab by assessment area are shown for males in Figure 11 and for females in Figure 12. The time series of sampled landings is shorter than for brown crab. The mean sizes of individuals in landings were relatively stable. In 2016-19, the mean size and the mean size of the largest 5% of both males and females were on average below the reference points in all assessment areas (Table 12). However, there is a weak positive trend in the mean size of the largest 5% since 2000 in the Hebrides and in Orkney. A decrease in the mean size and the mean size of the largest 5% of individuals was noted in the East Coast since 2008, before a slight rise in both males and females in 2019. A decrease in the mean size and the size of the largest 5% of males was noted in South Minch and Clyde since 2016. The size at first capture was generally above maturation size L_mat (Figure 11, Figure 12).

The sex ratio for velvet crab showed little evidence of a trend with males dominating in the landings, representing around 60% to 80% (by number) in the well-sampled areas (Figure 16).

3.2.4. Length Cohort Analysis

The results of assessments based on LCAs and per recruit analysis, summarising estimates of fishing mortality in relation to F_MSY are shown below. Estimates of fishing mortality in relation to previous assessments are presented in Figure 31 (males) and Figure 32 (females). Velvet crab biomass and yield-per-recruit plots for each assessment area are shown in Figure 37 (males) and Figure 38 (females).

Velvet crab in the Clyde, East Coast, and Orkney, were fished at levels above F_MSY (both males and females) in the most recent assessments. In the Hebrides and South East, males were fished at F_MSY while females were fished above F_MSY (Table 15). Assessment results for Shetland were deemed inconclusive due to contradictory results in the estimated fishing mortality when using the two alternate sets of biological parameters (see section below and discussion). No assessments were performed for the Mallaig, North Coast, Papa, Sule and Ullapool as the sampling data collected were considered insufficient to run LCAs.

Velvet crab stock status, relationship between F and F_MSY for 2006-08, 2009-12, 2013-15 and 2016-2019.

Assessment period		F (Fishing Mortality)
		2006- 2008	2009-2012	2013-2015	2016-19
Clyde	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
Hebrides	Males	ok	ok	ok	between	At FMSY
	Females	no	no	no	no	Above FMSY
North Coast	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Papa	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Shetland	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Sule	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
East Coast	Males	between	no	no	no	Above FMSY
	Females	between	no	no	no	Above FMSY
Mallaig	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Orkney	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
South East	Males	between	unknown	between	between	At FMSY
	Females	no	unknown	no	no	Above FMSY
South Minch	Males	no	no	no	no	Above FMSY
	Females	no	ok	no	no	Above FMSY
Ullapool	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown

3.2.5. Comparison with Previous Assessments

The current assessment uses a fixed length range to calculate an average fishing mortality and can be compared with previous assessments which used the same range (Mesquita et al., 2011; Mesquita et al., 2016; Mesquita et al., 2017; Mill et al., 2009). In the Hebrides, male fishing mortality increased to be at F_MSY (previously below F_MSY) in the most recent assessment while in the other areas the position of F relative to F_MSY remains unchanged. The estimated F for velvet crab has been found to be relatively stable over the time series in the Hebrides and Orkney areas (Figure 31 and Figure 32). Velvet crab F estimates for Shetland (using Shetland parameters) are much higher than those estimated elsewhere (Table 15, Figure 31 and Figure 32). This is due to the use of different growth rate (K) and natural mortality (M) parameters specific to Shetland (Table 6). To examine what underlies these differences, LCAs were run for all areas using both the Shetland and the rest of Scotland biological parameters and results compared (Annex C). Shetland’s higher natural mortality rate results in flat-topped YPR curves with both higher estimates of current F (F_male=2.3; F_female=2.6) and F_MAX (the F_MSY proxy) for both sexes compared with other areas (Figure 31, Figure 32 and Table 15). This is further discussed in section 4.3.

3.3 Lobster

3.3.1. The Fishery

The total tonnage of lobster landed in Scotland has consistently been much lower than that of crabs. However, reported lobster landings have increased substantially over the last 20 years, from 410 tonnes in 2000 to about 1,100 tonnes in 2020 (Figure 2 a). The average price per kilogram of lobster was stable at just over £10 per kilogram for a long period of time but has seen a significant increase since 2016 with an average price per kilo of £13.7 for the period 2016-20 (Figure 2 c). Between 2016 and 2020, the total value of the lobster fishery was around 80% that of the brown crab fishery (Figure 2 b). The annual lobster landings by assessment area are shown in Figure 5. Historically, the majority of landings of lobster in Scotland have been from the Hebrides, Orkney and South Minch, but these areas have been overtaken in recent years by landings from the South East and East Coast areas. The period between 1999 and 2004 was characterised by lower landings from all areas. This can be related to an increase in minimum landing size to 87 mm in 1999, with the effect on landings being evident for the following years. The same effect is not evident following the staged increase in the minimum landing size from 87 mm to 90 mm in 2018 for the west coast of Scotland (except the Solway Firth), although landings by area in this report are only presented up to 2019. Landings in 2006 do not seem to be comparable with those in the preceding years (particularly in the South East and East Coast) which could be due to the introduction of UK ‘buyers and sellers’ regulations, before which landings may have been under-reported. Landings from the South East and the East Coast increased continuously from 2006 to 2014 and accounted for almost 60% of landings into Scotland over the last four years (Table 10). Figure 8 shows the spatial distribution of lobster landings around Scotland in the period 2016-19. ICES rectangles 41E7 in the South East and 42E7 in the East Coast consistently have the largest landings. Small quantities of lobster were landed from grounds outside the assessment areas, including ICES rectangles to the west of Sule and the Hebrides; west of South Minch, to the south of the Clyde; and just outside the South East and East Coast areas.

3.3.2. Sampling Levels

The numbers of sampled lobsters, number of trips and percentage of sampled fishing trips are shown in Table 5. The percentage of trips sampled was generally less than 5% in most assessment areas, where daily inshore trips are common. The best sampled areas were the South Minch, South East, Hebrides, Orkney and Shetland. The number of sampling trips carried out in the Clyde and Papa areas remains lower than elsewhere. The overall number of fishing vessels exploiting the Papa Bank is low throughout the year – this implies a relatively high percentage of trips sampled compared with other areas such as the East Coast, which has a high number of animals measured but a low percentage of trips sampled. Length frequencies derived for these areas typically show a similar distribution to those from better sampled, adjacent areas and are therefore assumed to be representative, despite the low sampling levels. Sampling data were considered to be insufficient (low numbers and infrequent sampling) to run assessments in the Mallaig, North Coast, Sule and Ullapool areas (Annex A). These four areas represent only a small percentage of the total Scottish landings.

3.3.3. Size-based indicators and Sex Ratio

Size-based indicators for lobster landings by assessment area are shown in Figure 13 for males and in Figure 14 for females. The data are very noisy, and although males and females appeared to generally follow the same pattern of variation, there is little evidence of trends in any of the areas. Lobsters in the Clyde, South East and East Coast were noticeably smaller than in other areas over the full time series. A decline in the mean size of larger individuals can be observed in Shetland over the most recent eight years for both sexes. For males only, there has been a slight decreasing trend in the mean size of larger individuals in the East Coast since 2010, which has levelled out over the last three years. In Orkney, there is a decline in the mean size of larger male individuals in the past three years, while the mean size of large females increased. In the Hebrides, there has been a decreasing trend in males over the last fifteen years. Between 2016 and 2019, the overall mean size and the mean size of the largest 5% of males were generally below the reference points (Table 13). In the same time period, only the mean length of the largest females in Orkney was above the reference point. In the East Coast and South East, the size at first capture was above the size at first maturity L_mat for both sexes. In the other assessment areas, maturation size is estimated to be larger and size at first capture was below size at maturity L_mat. The sex ratio in landings for lobsters was close to 50% in all areas and showed no trends (Figure 17).

3.3.4. Length Cohort Analysis

The results of assessments based on LCAs and per recruit analysis summarising estimates of fishing mortality in relation to F_MSY are shown below. Estimates of fishing mortality in relation to previous assessments are presented in Figure 33 (males) and Figure 34 (females). Lobster biomass and yield-per-recruit plots for each assessment area are shown in Figure 39 (males) and Figure 40 (females).

In the most recent assessments, lobsters in all the areas were fished above F_MSY to some extent, particularly males. Fishing mortality was estimated to be above F_MSY for both males and females in the Clyde, South East, Shetland and South Minch. In the East Coast, Hebrides, Orkney, and Papa, fishing mortality for females was at or below F_MSY while males were fished above F_MSY (Table 16). No assessments were performed for Mallaig, North Coast, Sule and Ullapool, as the sampling data collected were considered insufficient to run LCAs.

Lobster stock status, relationship between F and F_MSY for 2006-08, 2009-12, 2013-15 and 2016-2019.

Assessment period		F (Fishing Mortality)
		2006- 2008	2009-2012	2013-2015	2016-19
Clyde	Males	no	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
Hebrides	Males	no	no	no	no	Above FMSY
	Females	ok	ok	ok	ok	Below FMSY
North Coast	Males	no	unknown	unknown	unknown	Unknown
	Females	ok	unknown	unknown	unknown	Unknown
Papa	Males	unknown	no	no	no	Above FMSY
	Females	unknown	ok	ok	ok	Below FMSY
Shetland	Males	unknown	ok	no	no	Above FMSY
	Females	unknown	no	no	no	Above FMSY
Sule	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
East Coast	Males	no	no	no	no	Above FMSY
	Females	no	no	no	between	At FMSY
Mallaig	Males	unknown	unknown	unknown	unknown	Unknown
	Females	unknown	unknown	unknown	unknown	Unknown
Orkney	Males	no	no	no	no	Above FMSY
	Females	ok	between	between	ok	Below FMSY
South East	Males	ok	no	no	no	Above FMSY
	Females	no	no	no	no	Above FMSY
South Minch	Males	unknown	no	no	no	Above FMSY
	Females	unknown	no	no	no	Above FMSY
Ullapool	Males	no	unknown	unknown	unknown	Unknown
	Females	ok	unknown	unknown	unknown	Unknown

3.3.5. Comparison with Previous Assessments

The current assessment uses a fixed length range to calculate an average fishing mortality and can be compared with previous assessments which used the same range (Mesquita et al., 2011; Mesquita et al., 2016; Mesquita et al., 2017; Mill et al., 2009). Shetland’s lobster results are only presented from 2009 onwards. The MoU between MSS and Shetland UHI for data provision means that recent data (sampled landings) are not directly comparable with data provided prior to 2009 (raised catch data including discards).

In the South East and Shetland, estimated F for both males and females increased and remained above F_MSY in the latest assessment. An increase in F was also found for males in the South Minch and East Coast. In the Clyde, estimated F decreased in 2016-19 for males and females but remains above F_MSY. Estimates of F for female stocks were generally lower than males, showing a slight decrease in relation to the previous assessments in the Hebrides and Orkney with F in the latter estimated to be below F_MSY for females (previously at F_MSY). In East Coast, the estimated F for females decreased and is now at F_MSY in the recent assessment. Estimates of F in Papa remained approximately the same in relation to previous assessments with a slight decrease in F for both males and females. The estimated F for lobster has been found to be relatively stable over the time series in the Hebrides area, however an increase in the estimated F for males was noted in 2016-2019 (Table 16, Figure 33 and Figure 34).