Population effects of shrimp trawl bycatch on Atlantic croaker

We used stage-within-age based matrix models of Atlantic croaker (Micropogo nias undulatus) in the Gulf of Mexico and the South and Mid-Atlantic bights to explore the population-level impacts of shrimp trawl bycatch on estuari ne-dependent fishes and to investigate tradeoffs between directed adult fis heries and bycatch mortality. The Gulf model reflected a rapidly declining population, while the Atlantic population showed a modest decline. Elastici ty analyses indicated that both populations were more sensitive to the summ ed survival of adults than first-year survival, particularly in the Gulf. C ontrary to our expectations, bycatch mortality on late juveniles was not th e most important factor affecting either population of Atlantic croaker, an d this result was robust to uncertainty in both adult and late juvenile mor tality estimates. Both populations were most sensitive to ocean larva morta lity, followed by mortality of estuary larvae and adults in the Gulf and of early juveniles and adults in the Atlantic. Nonetheless, bycatch mortality did have a large negative impact on population growth rates, and reducing late juvenile or adult mortality by about 35% in the Gulf or 5% in the Atla ntic should reverse population declines. Bycatch reduction devices currentl y in use can achieve these desired reductions.