Crab and lobster fisheries - stock assessments: results 2016 to 2019
Results of Scottish regional brown crab (Cancer pagurus), velvet crab (Necora puber) and lobster (Homarus gammarus) stock assessments carried out by Marine Scotland Science (MSS) for the period 2016 to 2019.
7. Figures
![shows a map with the crab and lobster fishery assessment areas in Scotland distributed around Scottish waters.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g03.png)
![displays the Scottish crab and lobster fishery statistics including landings into Scotland (top), landings total value in million pounds (middle) and price per kilo in pounds (bottom) for brown crab, velvet crab and lobster, 1974 -2020. Landings, total value and price show a general increase (although with some fluctuations) over the last 40 years.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g04.png)
![shows total landings of brown crab between 1974 and 2020 in each assessment area. Different trends are observed in each area but there is a general decrease in brown crab landings in recent years for those areas with larger landings.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g05.png)
![shows total landings of velvet crab between 1984 and 2020 in each assessment area. Landings appear relatively stable in most assessment areas.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g06.png)
![shows total landings of lobster between 1974 and 2020 in each assessment area. Landings in the EC and SE areas increased markedly in the early 2000’s and these two areas account for a large percentage of the total landings into Scotland.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g07.png)
![shows Brown crab landings by statistical rectangle between 2016 and 2020 landed by vessels from Scotland and Ireland. Scottish landings are distributed around Scotland mainland and islands while Irish landings are concentrated to the north of Ireland and Malin Shelf to the west of South Minch.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g08.png)
![shows Velvet crab landings by statistical rectangle between 2016 and 2020 Landings are distributed around the inshore waters of Scotland mainland and Islands.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g09.png)
![shows European lobster landings by statistical rectangle between 2016 and 2020 Landings are distributed around the inshore waters of Scotland mainland and Islands and a large proportion of landings has been fished in the East coast and South East areas.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g10.png)
![shows brown crab male trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g11.png)
![shows brown crab female trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g12.png)
![shows velvet crab male trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g13.png)
![shows velvet crab female trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g14.png)
![shows lobster male trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g15.png)
![shows lobster female trends in the mean size in landings, mean size of the largest 5% of individuals and size at first capture by assessment area in the period 1981-2019. Each of the mentioned variables are compared to the respective reference points. A minimum of 50 individuals was used each year to calculate mean sizes.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g16.png)
![shows brown crab sex ratio expressed as percentage of males in landings by assessment area in the period 1981-2019. There are large variations in sex ratio with some offshore areas dominated by females in the landings.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g17.png)
![shows velvet crab sex ratio expressed as percentage of males in landings by assessment area in the period 1987-2019. There are some relatively large variations in sex ratio with most areas dominated by males in the landings.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g18.png)
![shows lobster sex ratio expressed as percentage of males in landings by assessment area in the period 1981-2019. The sex ratio in landings for lobsters is close to 50% in all areas and shows no obvious trends.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g19.png)
![contains in the top left, a map of the study region in the east coast of Scotland with the dredge and trawl survey areas and stations sampled; in the top right there is a bathymetry map of the study area and in the bottom; in the bottom the figure shows the distribution of marine sediments in the study area from the British Geological Survey.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g20.png)
![contains in the top left, a map of the study region in the west coast of Scotland with the dredge and trawl survey areas and stations sampled; in the top right there is a bathymetry map of the study area and in the bottom; in the bottom the figure shows the distribution of marine sediments in the study area from the British Geological Survey.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g21.png)
![contains in the top left, a map of the study region in the Shetland Islands with the dredge and trawl survey areas and stations sampled; in the top right there is a bathymetry map of the study area and in the bottom; in the bottom the figure shows the distribution of marine sediments in the study area from the British Geological Survey.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g22.png)
![shows in the left column, variograms for the east coast of Scotland, estimating semi-variance with spherical and linear models. In the right column, kriged maps are presented showing predicted catch rates. There are five analysis scenarios considered displayed in this figure from top to bottom: all crabs (dredge), females (dredge), males (dredge), juveniles (dredge), and all crabs (trawl).](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g23.png)
![shows in the left column, variograms for the east coast of Scotland, estimating semi-variance with spherical and linear models. In the right column, kriged maps are presented showing predicted catch rates. There are five analysis scenarios considered displayed in this figure from top to bottom: all crabs (dredge), females (dredge), males (dredge), juveniles (dredge), and all crabs (trawl).](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g24.png)
![shows in the top, a variogram for the Shetland Islands, estimating semi-variance with spherical and linear models. In the bottom, a kriged map is presented showing predicted catch rates. There only scenario considered for Shetland and displayed in this figure is for all crabs caught on the dredge survey.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g25.png)
![shows the brown crab abundance indices by year for the east coast (top), west coast (middle) and Shetland (bottom), estimated from GAMs applied to dredge and trawl surveys in the period 2008-2020. A declining trend in crab abundance is noted for both surveys in the east and west coast of Scotland in recent years.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g26.png)
![shows the brown crab recruitment index by year in the east coast (top) and west Coast (bottom). A declining trend in recruitment is noted in the east and west coast of Scotland in recent years.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g27.png)
![displays the length frequency distribution of east coast brown crabs captured in the dredge (left) and trawl surveys (right) between 2008 and 2020. Calculated medians and means of the length distributions in each year are also displayed in the figure showing a relatively correlation.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g28.png)
![displays the length frequency distribution of west coast brown crabs captured in the dredge (left) and trawl surveys (right) between 2008 and 2020. Calculated medians and means of the length distributions in each year are also displayed in the figure showing a high correlation.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g29.png)
![displays the length frequency distribution of Shetland brown crabs captured in the dredge (left) and trawl surveys (right) between 2008 and 2020. Calculated medians and means of the length distributions in each year are also displayed in the figure showing a high correlation.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g30.png)
![shows the male brown crab average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. Estimated F has decreased in relation to the last assessment in all areas.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g31.png)
![shows the female brown crab average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. Estimated F has decreased in relation to the last assessment in all areas except for the East Coast and Shetland.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g32.png)
![shows the male velvet crab average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. The estimated F has been found to be relatively stable over the time series in the Hebrides, Orkney and South east areas and more variable in the other areas.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g33.png)
![shows the female velvet crab average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. The estimated F has been found to be relatively stable over the time series in the Hebrides, Orkney and South Minch areas and more variable in the other areas.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g34.png)
![shows the male lobster average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. In the East Coast, South East, Hebrides, South Minch and Shetland, estimated F increased in the latest assessment.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g35.png)
![shows the female lobster average fishing mortality (Fbar) time series for the last five assessments in relation to FMSY. 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.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g36.png)
![shows the male brown crab biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort while the maximum yield is generally found in the 50% to +50% effort interval.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g37.png)
![shows the female brown crab biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort while the maximum yield is generally found in the 50% to +50% effort interval.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g38.png)
![shows the male velvet crab biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort while the maximum yield is generally found in the 50% to +50% effort interval.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g39.png)
![shows the female velvet crab biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort while the maximum yield is generally found in the 50% to +50% effort interval.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g40.png)
![shows the male lobster biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort. For the majority of assessed stocks, an effort reduction of more than 50% would be required to achieve the maximum yield.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g41.png)
![shows the female lobster biomass and yield-per-recruit (YPR) predictions given changes from current effort by assessment area for years 2016-2019. Biomass shows a decreasing trend with effort while the maximum yield is generally found in the 50% to +50% effort interval.](/binaries/content/gallery/publications/research-analysis/2023/03/crab-lobster-fisheries-scotland-results-stock-assessments-2016-2019/SCT02239610681_g42.png)
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Email: carlos.mesquita@gov.scot
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