Size-at-maturity of Brown Crab (Cancer pagurus) in Scottish waters based on gonadal and morphometric traits

CRediT authorship contribution statement Carlos Mesquita: Conceptualization, Methodology, Formal analysis, Writing - original draft. Helen Dobby: Conceptualization, Writing - review & editing, Supervision. Stephanie Sweeting: Methodology, Data curation, Formal analysis. Catherine S. Jones: Supervision, Writing - review & editing. Graham J. Pierce: Conceptualization, Writing - review & editing, Supervision.Peer reviewedPostprin

Abundance and Spatial Distribution of Brown Crab (Cancer pagurus) from Fishery-Independent Dredge and Trawl surveys in the North Sea

Acknowledgements We would like to thank the MSS staff who participated in the east coast dredge surveys and IBTS quarter 3 surveys for the data sampling work that has been used in this study. Thanks to Andrzej Jaworski for providing advice on the use of geostatistical methods. Finally, would also like to thank the editor and two anonymous reviewers for their helpful comments. Funding This study was funded by the Marine Collaboration Research Forum (MarCRF), with Marine Scotland Science and the University of Aberdeen.Peer reviewedPostprin

Bioeconomic modelling of grey seal predation impacts on the West of Scotland demersal fisheries

The role grey seals have played in the performance of fisheries is controversial and a cause of much debate between fishers and conservationists. Most studies focus on the effects of seal damage to gears or fish and on prey population abundance but little attention is given to the consequences of the latter for the fisheries. We develop a model that quantifies the economic impact of grey seal predation on the West of Scotland demersal fisheries that traditionally targeted cod, haddock and whiting. Three contrasting fishing strategy scenarios are examined to assess impacts on equilibrium fleet revenues under different levels of seal predation. These include status quo fishing mortality (SQF, steady state with constant fishing mortality), open access fishing (bioeconomic equilibrium, BE) and the maximum economic yield (MEY). In all scenarios, cod emerges as the key stock. Large whitefish trawlers are most sensitive to seal predation due to their higher cod revenues but seal impacts are minor at the aggregate fishery level. Scenarios that consider dynamic fleet behaviour also show the greatest effects of seal predation. Results are sensitive to the choice of seal foraging model where a type II functional response increases sensitivity to seal predation. The cost to the fishery for each seal is estimated

CV12010

Use the URI link below to search the Marine Institute Data Discovery Catalogue for datasets relevant to this report.This report provides the results of the first underwater television on the ‘Porcupine Bank Nephrops grounds’ ICES assessment area; Functional Unit 16. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. The UWTV results and a scientific basis for survey based catch advice in 2013 are presented. In total 47 UWTV stations were successfully completed. The mean burrow density was 0.19 burrows/m² (empirical 95% confidence intervals are from 0.17-0.21). The final krigged abundance estimate was 992 million burrows with a relative standard error of 5% and an estimated stock area of 7,100km2. This abundance estimate can be considered as a conservative estimate given that the spatial coverage of the southern part of the ground was not complete. A correction factor of 1.26 is proposed based on expert judgments of burrow size and potential detection and identification biases. A yield and spawner per recruit analysis was used to estimate a harvest rate of 5.0% for the combined sex F0.1 and other F reference points. This harvest rate is low compared to other FUs and can be considered very conservative. Applying this harvest rate to the abundance observed in the survey and using a mean weight in the landings of 45.0g implies landings in 2013 of 1,770 t. The results here could form the basis of the catch advice for 2013

ICES 2005/Theme Session N ICES CM 2005/N:16 The potential impact of commercial fishing activity on the ecology of deepwater chondrichthyans from the west of Scotland

Since the 1970s the deepwater shelf edge habitat west of the British Isles has been targeted by commercial fishers. The fishery is aimed at teleosts such as ling, black scabbardfish and roundnose grenadier. A smaller component of the catch is, however, composed of Chondrichthyes, i.e. the elasmobranchs (skates & rays) and holocephalans (chimaeras). Until the early 1990s these were discarded, but now they are either actively targeted or retained as by-catch and landed for human consumption. Elasmobranchs are particularly sensitive to high harvesting levels because of slow growth rates, high longevity and low fecundity. A recent combined assessment by ICES of the two most important commercial species, Centroscymnus coelolepis and Centrophorus squamosus indicated drastic decline to less than 50% original biomass. However, landings data are unreliable and fisheries independent, species-specific data that might be used to quantify the effects of fishing in these areas are sparse because of the technological challenges and expense involved in fishing to these depths. In this study, data from scientific deepwater trawl surveys collected by FRS Marine Laboratory were carried out from 1998-2004 and interrogated. These data were examined for any evidence of a decline in abundance and compared with published data from MAFF surveys in the same region between [1970][1971][1972][1973][1974][1975][1976][1977][1978]. Despite the short time series there were indications of declining trends in CPUE for a number of Squaliformes between 1998 and 2004 and the overall catch rates of sharks are dramatically lower than those recorded from pre-exploitation surveys in the 1970s. These results highlight the need to continue fisheries-independent surveys of this vulnerable ecosystem