Diel and seasonal patterns of spotted gar movement and habitat use in the lower Atchafalaya River basin, Louisiana

We used radiotelemetry to determine diel and seasonal movements, habitat use, and home range behavior of 37 adult spotted gars Lepisosteus oculatus in the Atchafalaya River basin, Louisiana. The Atchafalaya River exhibits a distinct spring flood pulse each year, inundating a 3,640-km(2) floodplain that includes a complex network of canals, bayous, and lakes. During non-flood months, diel locations of 27 fish recorded at 2-h intervals (median = 24 locations/fish) indicated that most spotted gars were shoreline oriented (P < 0.0001), preferred submerged branches as cover and avoided areas of exposed bank (P < 0.0001). Median spotted gar movement rates were higher during summer (40.4 m/h) than fall-winter(15.1 m/h), and during both seasons,rate of movement and percentage of home range used were significantly greater at night during dawn, day, or dusk periods (P < 0.03). Increased nocturnal activity appeared to be related to feeding periodicity, as a substantially greater proportion (70%) of spotted gars collected at night (N = 30) contained food compared with dawn, day, and dusk samples (29%; N = 90). Seasonal movement studies (twice-weekly locations; N = 37 fish) indicated that spotted gar activity increased as water temperature and river stage rose in the spring,resulting in greater median movement rates (130.1 mid) and home ranges (265.1 ha) than during fall-winter (35.8 mid; 6.2 ha) and summer (34.6 mid; 10.5 ha). Spotted gar home ranges established during the hood pulse typically included large areas of inundated floodplain, which provided extensive areas of suitable spawning and nursery habitat.