Principal Investigator: Lawrence Rozas
Co-Principal Investigators: Rick Hart
External Collaborator: Marvin Mace (University of Louisiana at Lafayette)
Natural mortality is notoriously difficult to estimate directly, 
yet this parameter is an important input to many models of population dynamics including stock assessment models. Providing more precise, accurate estimates of natural mortality and investigating causes of variability in natural mortality rates would help improve stock assessment models and the management of fishery species.
The white shrimp, Litopenaeus setiferus, supports a valuable commercial fishery in the northern Gulf of Mexico. Juvenile white shrimp depend on estuarine habitats such as inundated salt marsh for food resources and protection from predators during this critical life history stage.
The goal of our study is to estimate natural mortality rates for juvenile white shrimp within a salt marsh system using two different methods. We will estimate natural mortality rates for different cohorts of juvenile white shrimp in the study area and examine possible causes for the variation in mortality rates among cohorts. This information can be incorporated
into a new stock assessment model currently being developed for white shrimp in the northern Gulf of Mexico to provide more accurate forecasts of adult abundance.
Habitat specific vital rates, such as mortality and growth, can be used not only in stock assessment models but also to assess the value of estuarine nursery areas for fishery species, such as white shrimp. Wetlands in the northern Gulf of Mexico provide critical habitat for juvenile white shrimp, but this habitat is disappearing at a relatively rapid rate due to a variety of causes. Identifying estuarine areas that are valuable for juvenile shrimp (i.e., areas where mortality is low and growth is rapid) would benefit both conservation efforts and fishery management.
