Citation:

Littles, C. PROVISIONING ECOSYSTEM SERVICES AND CLIMATE CHANGE: A CASE STUDY USING GULF OF MEXICO BROWN SHRIMP, FARFANTEPENAEUS AZTECUS. A Community on Ecosystem Services, Jacksonville, FL, December 05 - 09, 2016.

Impact/Purpose:

Climate change is anticipated to affect near-shore habitats due to rising sea level, changes in salinity due to changes in precipitation, and changes in water temperature and acidity, and these may result in changes to the production of coastal ecosystem services. In this study, the potential effects of climate change on brown shrimp fisheries in the Gulf of Mexico was investigated through a combination of forecasted changes to critical habitat, shrimp population dynamics, and fishing rates. The modeling revealed that while brown shrimp populations may be resilient to moderate losses of marsh habitat area, they may not be resilient to a combination of climate-driven habitat loss and reduced juvenile shrimp recruitment rates (such as might be caused by changes in salinity, temperature or acidity) at current fishing rates. This work is a component of SHC Project 2.61, Task 3, research that seeks to develop a methodology for assessing the vulnerability and resilience of coastal ecosystem services to the effects of climate change.

Description:

Brown shrimp are commercially important shellfish that support one of the largest fisheries in the southeastern United States, contributing to a shrimp harvest revenue that can exceed $100 million per year. Therefore, understanding how climate-driven changes in habitat availability might affect current and future shrimp productivity is fundamental to developing optimal management strategies. We developed a theoretical framework to link life stage-specific demographic parameters to fishable stock abundance and investigated the effects of changes in density-dependent settlement, assumed to reflect differences in marsh habitat availability, on long-term population abundance. By working successively through Beverton-Holt relationships and incorporating catch data and fisheries-independent abundance estimates into a Bayesian modeling framework, we assessed the degree of density dependent settler survival underlying observed population trends over a 25 year period. The fitted model served as a baseline for projecting stock abundance over the next 20 years and altered our underlying assumptions of density-dependence. We explored how a 10-50% change in the degree of density-dependence, a possible climate change scenario, affected the estimated recruit and adult populations relied upon by Louisiana fishermen. Although external, market-driven factors will largely drive commercial fishing rates, our framework addresses stock availability with potential implications for pending climate change in the Gulf of Mexico. Simulated results suggested that Louisiana brown shrimp catch rates could be fairly resilient to moderate (10-25%) declines in marsh habitat. However, if the level of density-dependent settlement increased by 50% (i.e., 50% decline carrying capacity), the population could not sustain even the average fishing pressure exhibited over the study area during the previous ten years. State and federal agencies working to sustain and protect food-provisioning ecosystem services on the Gulf coast may consider prioritizing habit protection and restoration efforts to mitigate some of the more uncertain effects of climate change (e.g., ocean acidification and altered circulation patterns) on commercial shrimp fisheries. We present a framework for evaluating how actions targeting habitat preservation and restoration may ultimately inform this important food provisioning ecosystem service.

Record Details: