Striped Bass Morone saxatilis movement in a large southeastern river system

Striped Bass Morone saxatilis are a valuable commercial and recreation fishery resource and fill important ecological roles within an ecosystem. Migratory behaviors of coastal Striped Bass are diverse and vary by latitude along the US Atlantic coast. Northern populations are anadromous, with spawning occurring in tidal freshwater/brackish rivers and adults leave spawning locations during the winter to conduct north-south coastal migrations. Southern populations (below Cape Hatteras, NC) are typically resident and potamodromous, completing full life cycles within river systems, and do not migrate along the Atlantic coast. The objective of this study was to describe daily movement patterns and centers of attraction (e.g., spawning and resting stages) of Striped Bass in the Great Pee Dee River, South Carolina. Ten fish were implanted with hydroacoustic transmitters between 2013 and 2016. Daily movement and behavior are described using the state-space model with a two-dimensional spatial coordinate system. A total of 94,857 data points were recorded across all individuals and receivers. Two movement patterns were observed. One group completed a seasonal migration (i.e., were recorded swimming upstream or downstream) that coincides with spring spawning season. A second group was present in the lower river section and Winyah Bay during the winter for three consecutive years but were never observed migrating up the Great Pee Dee River during the spring. One individual was documented swimming 80 river km north in the Atlantic Intracoastal Waterway, suggesting there are important overwintering locations outside their natal river. Additionally, there were significant gaps in observations for all individuals, particularly in the summer. It is possible fish are leaving the main stem in search of thermal refuge within small tributaries. Identifying these overwintering areas and tributaries that serve as summer refuge is needed to determine stressors and fishing pressure of this important species.