Habitat Selection of Gulf-Strain Striped Bass, \u3ci\u3eMorone saxatilis\u3c/i\u3e: Relationships to Dynamic Abiotic Environmental Characteristics Within the Biloxi River, Mississippi

The purpose of this project was to provide insights about the short- and long-term patterns of habitat selection of Gulf-strain Striped Bass, Morone saxatilis, based on spatially and seasonally variable abiotic environmental characteristics (water temperature, dissolved oxygen (DO), salinity, specific conductivity, and pH) in the Biloxi River, MS system. Juvenile hatchery-reared and feral adult Gulf-strain Striped Bass were acoustically-tagged and continuously monitored via active and passive telemetry from November 2012 – June 2014. Each month the available abiotic environmental characteristics of 40 random locations within the Biloxi River, along with sub-habitat conditions occupied by acoustically-tagged Gulf-strain Striped Bass, were sampled vertically at 1 m intervals from the surface to the bottom of the water column. Abiotic sub-habitats selected by juvenile and adult Gulf-strain Striped Bass were identified and compared to random mean abiotic conditions available in the river. During the acclimatization period to the Biloxi River, juvenile hatchery-reared Gulf-strain Striped Bass initially remained near the stocking site in sub-habitats that provided deeper depths, warmer temperatures, and higher salinity compared to other habitats within the river. Initial sub-habitat abiotic conditions may have facilitated recovery from stressors and disorientation associated with stocking. Two weeks following the stocking event, juveniles dispersed away from the release site and occupied sub-habitats with abiotic environmental characteristics that resembled background conditions of the Biloxi River. As acoustically-tagged Gulf-strain Striped Bass grew and acclimatized to the Biloxi River over the 20 month study period, seasonal patterns of habitat selection were apparent. During the fall, winter, and spring seasons, variable DO concentration and water temperatures at depth strongly influenced sub-habitat selection of both juvenile and adult Gulf-strain Striped Bass. In fall and winter, juveniles and adults were consistently located in warmer water temperatures and deeper habitats; whereas, in spring, Gulf-strain Striped Bass selected deep areas with DO \u3e 7 mg/L. During summer, however, differences between Gulf-strain Striped Bass sub-habitats and background conditions of the Biloxi River were not clear. Although juveniles and adults were located in deep areas of the upper and lower regions of the Biloxi River, all other measured abiotic variables resembled the mean river abiotic condition characterized by DO concentrations greater than 5 mg/L and water temperatures of about 27.5°C. Ontogenetic trends in preferred habitat were evident during fall and winter when juvenile and adult sub-habitat selection was influenced by spatially-heterogeneous and vertical gradients of increased salinity at depth along the river continuum. Also, seasonal and annual variability in discharge greatly affected the decay of abiotic gradients spatially and vertically throughout the Biloxi River. Overall, the continual flux in abiotic environmental characteristics of a lotic system resulted in seasonally variable dispersal and habitat selection patterns for hatchery-reared juveniles and feral adults Gulf-strain Striped Bass in the Biloxi River