Scottish Marine and Freshwater Science Vol 12 No 4
A major problem faced in commercial crustacean fisheries, and the research and management of such fisheries, is the potential effect of discarding practices on survival and condition of non-retained catch. This report describes the results of trials undertaken to estimate survival rates of discards in the Orkney brown crab fishery.
Data and Resources
- Table 1 - Number of brown crabs collected for each observer trip by datecsv
Table 1 - Number of brown crabs collected for each observer trip by date...
- Table 6 - Number of individuals collected per treatment and damage index during the projectcsv
Table 6 - Number of individuals collected per treatment and damage index...
- Table 7_Model fit statistics for GLM/GAM models of survival of brown crabs in creelscsv
Table 7_Model fit statistics for GLM/GAM models of survival of brown crabs...
- Table 8_Estimated survival rates of crabs in creelscsv
Table 8_Estimated survival rates of crabs in creels
- Table 9_Model fit statistics for GLM/GAM models of survival of brown crabs in tankscsv
Table 9_Model fit statistics for GLM/GAM models of survival of brown crabs...
- Table 10_Estimated survival rates of crabs in tankscsv
Table 10_Estimated survival rates of crabs in tanks
|Release Date|| |
|Spatial / Geographical Coverage Location|| |
|Temporal Coverage|| |
2016-01-01 to 2017-09-30
UK Open Government Licence (OGL)
|Data Dictionary|| |
This study combined RAMP (reflex action mortality predictors) with vitality scores and the likelihood of survival for each vitality category to estimate survival rates of discards in the Orkney brown crab fishery. The vitality reflexes used in this study were similar to those established by Stoner (2012) and based upon behavioural responses. The study was divided in two phases: Phase I considered crabs smaller than the then-current (2016) 140 mm carapace width MLS (Minimum Landing Size) and Phase II considered legal-sized crabs. Two experimental set-ups were used, namely creels and tanks, each comparing control and treatment groups. Four categories of treatments were considered: missing limbs, recently moulted crabs, black spot and berried females were tested against a control group. In total, 265 brown crabs were collected for observation, of which 162 were females and 103 were males. Reflex impairment was closely related with vitality and damage scores showed more crabs died when scored 3 than when scored 2/1. Tank trials excluded all individuals that died when temperatures exceeded 16.2oC. Results obtained from the creel trials, exposed to ambient environmental temperature, were considered to show a clearer picture of the fate of brown crab discarded - an overall estimated survival rate of 92.7% across all groups in comparison with tanks with 90.3%.
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