A yield-per-recruit model for sequential fisheries and its application in evaluating the management strategy of changing incidental inshore fishing mortality

Yield-per-recruit (YPR) analysis is commonly used to test alternative management strategies when historical information on recruitment for the fish population being studied is limited. Like many other types of fisheries models, a primary assumption implied in YPR models is randomness in the distribution of fish and effective fishing efforts throughout the fishery. However, in practice, this assumption is rarely satisfied because spatial distribution of many fish populations is not random and the deployment of fishing efforts tends to target the area where fish of commercial sizes are abundant. In this study, we propose a YPR model for sequential fisheries that incorporates size-dependent difference in spatial distributions of fish and differences in selection patterns of fishing gears between inshore and offshore waters. We apply the proposed YPR model to evaluate the management strategy of changing incidental inshore fishing mortality for simulated fisheries based on redfish, Centroberyx affinis, and tiger flathead, Neoplatycephalus richardsoni, along the New South Wales coast (Australia). This study demonstrates a linkage between the fishing mortality on inshore grounds and YPR for both redfish and tiger flathead. Changes in YPR resulting from changes in the inshore incidental fishing mortality were more pronounced for redfish which displays a more consistent size-dependent offshore distribution.