Discard Mortality Estimation of Yellowtail Flounder Using Reflex Action Mortality Predictors

The southern New England mid-Atlantic stock of yellowtail flounder Limanda ferruginea has a history of substantial discards, and the current stock assessment assumes 100% discard mortality. A controlled experimental trawl was used to test seven reflex actions, which in combination make up the reflex action mortality predictors (RAMPs), from stressed and unstressed yellowtail flounder. Tow time and air exposure were tested to identify their effects on mortality. Mortality was significantly related to reflex impairment. Exposure to air was the more influential stressor in the survivability of yellowtail flounder, suggesting that discard mortality in the fishery could be reduced by limiting the duration of on-deck air exposure for the fish. An example application of RAMP monitoring demonstrates a 42–73% range of discard mortality estimates from the southern New England trawl fishery. The reflex impairment–mortality relationship enables the estimation of discard mortality aboard commercial fishing vessels, which will lead to more accurate estimates of yellowtail flounder discard mortality. Received September 13, 2011; accepted November 22, 2011