ASSESSING DISCARDING AT SEA USING A LENGTH-STRUCTURED YIELD-PER-RECRUIT MODEL

Discarding at sea is a common practice in fisheries. Part of the catch is often discarded because fish are too small to be marketed, or are bycatch. Regulations such as trip limits or quota limitations also pro vide fishermen with a strong incentive to discard fish that are above their quota and to high grade to maximize profits. Almost all fish dis carded at sea die. However, the impacts of discarding at sea have not been evaluated in many fisheries. Because the probability of a fish be ing discarded is usually dependent upon its length, a length-structure d model is appropriate for evaluating discarding. In this study, we pr opose an approach to evaluating the impacts of discarding at sea using a length-structured yield-per-recruit model. As an example, the propo sed approach was applied to data from the Oregon flatfish fishery. (C) 1997 Elsevier Science B.V.