Working Group on Crangon Fisheries and Life History (WGCRAN; outputs from 2021 meeting).
The ICES Working Group on Crangon Fisheries and Life History (WGCRAN) examines the various interactions of the brown shrimp to better understand the species.
Stock status indicators were deduced from scientific surveys and indicated (1) a high shrimp biomass in 2018 compared to the years before and after, (2) a lower fraction of large shrimp compared to previous years, especially in 2019 and 2020, and (3) an above-average total mortality in 2019. North Sea landings were exceptionally high in 2018, but below average in 2019 and 2020 when compared to the mean of the last two decades. Total effort in 2018 was above average, but a distinct effort reduction occurred in the following years due to storage and processing bottlenecks in the industry.
Average Landing Per Unit Effort (LPUE) in 2018 was almost twice as high as in 2017, the year with the lowest value of the times-series. In the following years LPUE decreased by about 30%. The high LPUEs in 2018 were supported by a strong shrimp cohort entering the fishery in autumn 2018. LPUEs in the first half of 2019 were still generated by the overwintering 2018-cohort. These high LPUE values, were followed by moderate and below-average values in 2020, with Germany and Denmark showing the lowest values. To ensure standardized effort data and investigate spatial patterns, Vessel Monitoring System (VMS) and logbook data were analysed. Here, LPUEs showed a significant negative trend in the first quarter for all regions, with the steepest decrease in the North. Up to 86% of the variability in summer landings in German and Danish waters could be explained by the effort in the preceding winter months in two southern areas. Altogether this hints toward a possible impact on the following recruitment by excess fishing effort in winter.
Existing and planned measures of the self-management were evaluated and tested. Undersized shrimp in catches decreased after the introduction of the self-management, suggesting a positive effect of mesh size increase on the population structure. The Harvest Control Rule failed to protect the poor stock in the Northern region in 2016 and 2017, mainly because reference values are too low and because higher catches in the southern regions managed to keep the mean LPUE just above the reference values. National sampling campaigns started to quantify bycatches and test the “de minimis” exemption in the brown shrimp fishery.
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