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

Abstract
We used radiotelemetry to determine diel and seasonal movements, habitat use, andhome range behaviour of 37 adult spotted gars (Lepisosteus oculatus) in the Atchafalaya Riverbasin, Louisiana. The Atchafalaya River exhibits a distinct spring flood pulse each year,inundating a 3,640-km2 floodplain that includes a complex network of canals, bayous, and lakes.During nonflood months, diel locations of 27 fish recorded at 2-h intervals (median = 24locations/fish) indicated that most spotted gars were shoreline oriented (P < 0.0001), preferredsubmerged branches as cover, and avoided areas of exposed bank (P < 0.0001). Median spottedgar movement rates were higher during summer (40.4 m/h) than fall-winter (15.1 m/h), and duringboth seasons, rate of movement and percentage of home range used were significantly greater atnight than during dawn, day, or dusk periods (P < 0.03). Increased nocturnal activity appeared tobe related to feeding periodicity, as a substantially greater proportion (70%) of spotted garscollected 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 garactivity increased as water temperature and river stage rose in the spring, resulting in greatermedian movement rates (130.1 m/d) and home ranges (265.1 ha) than during fall-winter (35.8m/d; 6.2 ha) and summer (34.6 m/d; 10.5 ha). Spotted gar home ranges established during theflood pulse typically included large areas of inundated floodplain, which provided extensive areasof suitable spawning and nursery habitat.
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1999
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