Abstract

Warming temperatures can alter the life histories of marine organisms, including shifting body sizes, the timing of migratory cues, and habitat use. The Atlantic white shrimp Penaeus setiferus (hereafter white shrimp) is an ecologically important species supporting significant fisheries in the southeastern USA. White shrimp move across the estuarine-oceanic continuum, from small shallow estuarine habitats as juveniles to nearshore oceanic waters as adults. Using six separate fisheries-independent datasets spanning estuarine creeks, estuarine sounds, and nearshore habitats, we investigated long-term trends in salinity, water temperature, and shrimp sizes across South Carolina and Georgia, USA, over more than 30 years. Salinity only increased significantly for estuarine sound sampling in South Carolina, but not for other habitats; however, temperature increased significantly in all three habitats. We also documented concurrent changes in the sizes of white shrimp that were especially evident in estuarine sounds during the fall, with shrimp size declining linearly at an average rate of 5 mm decade−1. Concurrently, adult sizes in coastal waters remained unchanged across surveys and seasons. One potential mechanism for these observed changes is that warming water temperatures are altering shrimp growth patterns and shifting the phenology of their offshore migrations, leading to reduced sizes of shrimp sampled in estuarine sounds, but additional research is needed to test this hypothesis. This serves as a case study of the potential impacts of more than three decades of changing climate and highlights the utility of long-term fisheries-independent datasets for conducting integrated ecological assessments.