Selecting species specific vitality metrics to predict red king crab (Paralithodes camtschaticus) discard survival
Introduction
Animals incidentally caught and discarded in commercial fisheries are exposed to processes and conditions that can contribute to physical and physiological stress and consequent injury and death (Alverson et al., 1994). These interactions can lead to immediate or delayed mortality (Davis, 2002). In federally managed US fisheries, full accounting of fishing mortality is required by regulation (50 Code of Federal Regulations (CFR) §600.350). However, it is challenging to conduct a study where animals can be assessed and delayed discard mortality outcomes determined over the broad range of real fishing conditions. The development and application of rapid and non-invasive methods to assess impacts of fishing-induced stress and injury are needed to expand the scope of research investigations to be sufficiently representative of a fishery and to allow for the identification of variables that influence survival outcomes. To that end, stress and injury assessment methods that relate behavioral and reflex responses to survival outcomes (‘vitality metrics’) have been applied to several taxa. These include sharks (Squalus acanthias, Mandelman and Farrington, 2007; and Prionace glauca, Campana et al., 2009), roundfish (Theragra chalcogramma, Davis, 2007; Oncorhynchus kisutch, Raby et al., 2020), flatfish (Hippoglossus stenolepis, Davis and Olla, 2001), and crustaceans (Chionoecetes bairdi and Chionoecetes opilio, Stoner et al., 2008; Hammond et al., 2013; Yochum et al., 2015; and Cancer magister, Yochum et al., 2016). These efforts were based largely on applying species-specific vitality metrics. However, in Rose et al. (2013) the vitality metrics developed for C. bairdi and C. opilio (Stoner et al., 2008) in the Alaska groundfish bottom trawl fishery were additionally applied to red king crab (RKC, Paralithodes camtschaticus) bycatch. These metrics were unsuccessful in predicting RKC post-release mortality, suggesting the importance of developing metrics specific to this species.
Red king crab are currently designated as prohibited species catch (PSC1) in Alaska groundfish bottom trawl fisheries, requiring immediate discard from the below-deck factory (50 CFR 679.21(a)(2)(ii)). In the offshore (factory catcher-processor sector) bottom trawl fishery, the catch (including bycatch), is deposited on deck, transferred to below-deck holding tanks before being weighed, sorted, and processed (or discarded) in the vessel factory. The process from deck to discard can take up to several hours, depending on a suite of factors (e.g., total catch size, diversity of catch, factory processing capacity) (Personal communication J. R. Gauvin). Rose et al. (2013) examined the effect of the trawling catch process on RKC at the point of deposit on deck, meaning that the potential for additional stress and injury associated with the factory holding, handling, and sorting process remains unexplored. Given the morphological and physiological traits of crustaceans (e.g., brittle exoskeleton, limited biomechanical flexibility, constrained tactile sensory system), such as RKC, these handling and discard processes result in additional opportunities for stress and injury. Therefore, in addition to developing vitality metrics specific to RKC, the full catch and discard process must be considered in their development.
We addressed the relationship between vitality metrics and post-release mortality in trawl-caught RKC by evaluating a suite of species-specific vitality metrics developed using previous studies, laboratory trials, and recommendations by commercial fishermen. Selected metrics were advanced for at-sea testing, providing the first in situ assessment of the relationship between RKC impairment and delayed mortality based on assessment both on deck and after factory processing.
Section snippets
Materials and methods
A suite of 14 candidate vitality metrics were identified based on biological and physiological characteristics specific to RKC, metrics used for other crab species (Stoner et al., 2008; Hammond et al., 2013; Rose et al., 2013; Yochum et al., 2015, 2016), and observations provided by commercial crab fishermen (see supplemental Table A.1). In August 2018, these candidate metrics were explored using a series of metric-specific stimulations on 14 adult RKC at the Alaska Fisheries Science Center
Results
Fourteen candidate vitality metrics (supplemental Table A.1) and associated behavioral responses were explored on 14 RKC in the laboratory. The six candidate metrics that were present in all laboratory crab and were unaffected by the 25-minute air exposure were advanced for at-sea testing on RKC caught during commercial groundfish bottom trawl fishing. In addition, during consultation with members of the fishing industry, following laboratory testing, an additional metric was recommended
Discussion
Crab are susceptible to heightened stress, injury and ultimately mortality during the fishing, catch handling, and discarding processes. Current regulations mandate the post-factory discarding of RKC to ensure they are subject to fishery observer sampling (50 CFR 679.21(a)(2)(ii)). Although our review of the literature found no previous studies examining factory-induced stress and injury to crabs, our findings were consistent with our expectations that higher levels of impairment were found in
CRediT authorship contribution statement
Cory Lescher: Conceptualization, Investigation, Methodology, Writing - original draft. Noëlle Yochum: Methodology, Writing - review & editing. Brad Harris: Supervision, Funding acquisition, Writing - review & editing. Nathan Wolf: Writing - review & editing. John Gauvin: Conceptualization, Project administration.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors wish to thank the Northstar fishing company, specifically the captain and crew of the F/T Cape Horn; the O’Hara Corporation; and US Seafoods for assistance with data collection. Dr. Robert Foy and the Alaska Fisheries Science Center Kodiak Laboratory generously allowed us to use their lab facility and captive red king crab. The manuscript benefitted from comments from reviewers associated with the NOAA internal review process and from Dr. Robert Murphy from the FAST Lab. This work
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