Implications of Discard Mortality on Catch Retention Scenarios

Full and maximized retention have been considered as possible management scenarios for the groundfish fishery in New England.  A full or maximized retention policy could potentially reduce waste from commercial fisheries by converting discards into retained catch, and could improve cost-effectiveness of fisheries monitoring.  The implications of these policy options on stock size depends on discard mortality rates among the various species in the groundfish complex.  We examined discard mortality rates of otter trawl and scallop dredge caught yellowtail, winter and windowpane flounder using Reflex Action Mortality Predictor (RAMP) methods, and found a range of mortality rates from 35 to 90% among the species.  While yellowtail and windowpane flounder display high discard mortality rates (80-90%), winter flounder discard mortality was estimated to be approximately 35-50%.  These results imply that a full or maximized retention policy could be beneficial for reducing waste of species with high discard mortality rates, but may produce higher overall mortality on stocks with low or moderate discard mortality rates.  Continued investigations of discard mortality rates for the species managed in the groundfish complex is required to understand the implications of a full retention policy on overall stock health.