The survival of rajids discarded in the New England scallop dredge fisheries
Abstract Due primarily to regulatory factors, skates (family Rajidae) account for nearly half the total bycatch discarded during commercial fishing operations in the U.S. portion of the Northwest Atlantic Ocean. In this region the New England scallop dredge fishery has the second highest skate discard rate; however, no information regarding their resiliency to interaction with this gear type exists. To gain insight into species-specific mortality rates, 295 tows were conducted throughout six research cruises (2012–2013 fishing season), with a total of 4216 skates (little skate, Luecoraja erinacea , winter skate, Leucoraja ocellata , and barndoor skate, Dipturus laevis ) evaluated and scored using reflex impairment and injury (i.e., overt physical trauma) indicators. To quantify mortality rates associated with these indicators, 334 skates were retained in an on-deck refrigerated flow-through seawater system and monitored every six-hours until the end of a trial. This study also assessed the effect of fishing conditions/practices and individual traits on post-release mortality. Data suggest that species-specific differences exist wherein winter skate are likely the most resilient (45.4% mortality) to capture and handling, little skate have a moderate capacity to deal with these pressures (62.7% mortality), and barndoor skate appear to be the most susceptible (99.9% mortality). In addition, little and winter skate mortality rates were both influenced by tow duration, while fishing depth and temperature gradient had an effect on little skate and air exposure on winter skate. Highlights Fishery-scale short-term survival estimated as 54.6% for winter skate, 37.3% for little skate, and 0.1% for barndoor skate. Little skate mortality rates are likely influenced by tow duration, fishing depth, and temperature gradient. Winter skate mortality rates are likely influenced by tow duration and air exposure experienced on-deck.
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