Prevalence and effects of rhizocephalan (Cirripedia: Briarosaccus callosus) parasitism and assessment of post-capture survival using the reflex action mortality predictor (RAMP) method on the deep water Porcupine crab (Neolithodes grimaldii) captured on the Labrador Shelf in the Northwest Atlantic

Furey, Greg (2016) Prevalence and effects of rhizocephalan (Cirripedia: Briarosaccus callosus) parasitism and assessment of post-capture survival using the reflex action mortality predictor (RAMP) method on the deep water Porcupine crab (Neolithodes grimaldii) captured on the Labrador Shelf in the Northwest Atlantic. Masters thesis, Memorial University of Newfoundland.

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Abstract

The porcupine crab (Neolithodes grimaldii) is a deep water (>800m) species of king crab (Lithodidae) and little is known about its biology, ecology, and distribution. Historically, high bycatch rates of porcupine crab have been observed in gillnet fisheries targeting Greenland halibut (Reinhardtius hippoglossoides) in the northwest Atlantic. As there is currently no directed fishery for the porcupine crab in the north Atlantic the information collected in this study will be of interest to science, industry, and fisheries management. The results of this project will provide a basis to make informed decisions at the forefront on the sustainability of a potential fishery for this renewable resource. This thesis collected data on the prevalence of the rhizocephalan parasite (Briarosaccus callosus) infesting the porcupine crab which was found to be high (21%) compared to other species of open water king crab. Morphological and reproductive effects of B. callosus on the porcupine crab were also observed. The parasite sterilized male and female porcupine crabs. The parasite correlated with reductions in size of chelae height, length of the first and second merus, and carapace length in infested males, however, females had increased carapace and merus length. The post-capture survival of porcupine crab captured incidentally in gillnets targeting Greenland halibut was also determined using the reflex action mortality predictor (RAMP) method. The survival rate was high (74%) for crabs when removed from gillnets without extensive trauma and held 5-9 days in holding tanks aboard a commercial vessel. The survival rate was greater for crabs that were removed without extensive trauma (74%) and crabs that were selected in the second year that had incurred trauma from gear or rough handling (28%). Using the RAMP method revealed stark differences between porcupine crab captured in gillnets and previous studies conducted on bottom trawl captured king crab. Porcupine crab appear to be in a heightened state during capture and removal from gillnets reducing the ability to predict mortality using the RAMP method as they failed few reflex actions. Analyzing these results revealed that mortality could not be predicted with a high amount of confidence as a low amount of variability was explained by the models used (5-15%).

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