Modeling the Effects of Vital Rate Manipulation and Management Scenarios to Predict the Population Impact of Restoration Programs on an Unrecovered Coastal Population of Striped Bass

Abstract

AbstractStriped Bass Morone saxatilis have supported important fisheries along the Atlantic coast of North America. However, the species experienced major declines due to overharvest, water quality degradation, and dam construction. Restoration efforts have been successful for specific stocks but unsuccessful for the Striped Bass population in the Neuse River of North Carolina. Ongoing research programs have estimated stage‐ and source‐specific mortality rates to identify mechanisms associated with the lack of recovery of the population. These demographic data are useful; however, they give little insight into the effectiveness of potential restoration programs. To develop effective management strategies, we used estimated mortality rates from the literature to build an age‐structured population model. We estimated that if vital rates remained constant, the Neuse River adult Striped Bass population would consist of 18,457 individuals (95% credible interval = 8,176–34,314). We then conducted a life stage simulation analysis to determine the adult population abundance and age structure that would result from a 50% decrease of the following: juvenile and adult natural mortality, recreational discard and harvest, and commercial discard and harvest. Finally, we simulated the potential impacts of six possible management scenarios on population abundance and age structure. We determined that the abundances of adults (age 3+) and older adults (age 6+) were most sensitive to natural mortality of juveniles and adults and next most sensitive to commercial harvest and discard. We further estimated that eliminating all fishing mortality would have the greatest impact on the population and would result in a 26‐fold increase in abundance of age‐6+ adults. Our results suggest that high mortality rates are preventing the development of a sufficient abundance of adult spawning stock. We recommend that managers use this model to identify the most effective management scenario—given specific goals and constraints—to help increase Striped Bass abundance in the Neuse River.