Brown Crab Cancer pagurus Discard Mortality Study
Recent studies of reproductive parameters in brown crab in Orkney have shown that there is a strong negative relationship between gonadosomatic development and damage to individuasl. This means that heavily damaged crabs, even if they are sexually mature, make no contribution to spawning activities for at least the season following that damage.
Given that the scored damage in this study was not associated with the fishing operations during which the crabs were collected, it is unclear whether the damage was a result of previous fishing activities (principally discarding) of occurred naturally. This project therefore looks to establish whether discarding of brown crabs causes the type of damage that impacts upon spawning capability, and to explore the options for mitigating these impacts through improved discard handling practice, gear selectivity or technical measures.
This project will be undertaken within 2016/2017
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Brown Crab Cancer pagurus Size at Maturity Study
The role of establishing the size of maturity of a species within a commercially exploited fishery is crucial for ensuring the longevity and sustainability of a stock. As fishing pressures can influence size at maturity it is important to undertake size at maturity studies every four years to monitor any changes, with the last study in Scotland conducted in Shetland in 2007 (1,2).
Geographic location is also known to affect size at maturity within other crustacea through the effect of environmental variables such as Sea temperature, salinity and food availability, with increases of latitudeue northwards causing species to grow and mature slower. Therefore to evaluate the impact of fishing and environmental variables on C.pagurus within the Orkney Fishery this study will compare and contrast size at maturity with historical literature to see if such spatial variation exists.
This study also forms the most northerly sample area within a current national study being co-ordinated by Bangor Universities Fisheries and Conservation Sciences group. This study will compare size at maturity around the UK and Ireland, with 6 other institutions involved.
This study has now been completed with the results published within the ICES Journal of Marine Science: Reproductive traits and factors affecting the size at maturity of Cancer pagurus across Northern Europe https://doi.org/10.1093/icesjms/fsw081
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(1) Tallack S.,M.,L.,(2007) J. Mar. Biol. Ass. U. K., 87, 507-515. http://dx.doi.org/10.1017/S0025315407054100
(2)Tallack S.,M.,L.,(2007) J. Mar. Biol. Ass. U. K., 87, 1181-1189. http://dx.doi.org/10.1017/S0025315407054094