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, 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 nonflood months, diel locations of 27 fish recorded at 2-h intervals (median ϭ 24 locations/fish) indicated that most spotted gars were shoreline oriented (P Ͻ 0.0001), preferred submerged branches as cover, and avoided areas of exposed bank (P Ͻ 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 than during dawn, day, or dusk periods (P Ͻ 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 ϭ 30) contained food compared with dawn, day, and dusk samples (29%; N ϭ 90). Seasonal movement studies (twice-weekly locations; N ϭ 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 m/d) and home ranges (265.1 ha) than during fall-winter (35.8 m/d; 6.2 ha) and summer (34.6 m/d; 10.5 ha). Spotted gar home ranges established during the flood pulse typically included large areas of inundated floodplain, which provided extensive areas of suitable spawning and nursery habitat.

Sulfur stable isotope indicators of residency in estuarine fish

“…7) that was not readily expected given the observed high abundance of gar in SAV beds during the summer collections. But among the upper-estuary species that have strong freshwater affinities, gar are often found in higher-salinity habitats and may move downestuary to overwinter in deeper depressions (Lambou 1952;Snedden et al 1999;Love 2004). Gar are long-lived species (Love 2004) and consume marine species such as blue crabs (Lambou 1952), so that partial retention of the marine d 34 S signal from winter diets could explain the high d 34 S values observed for upper-estuary gar collected in summer.…”

A preliminary analysis of the correlation of food-web characteristics with hydrology and nutrient gradients in the southern Everglades

“…Florida gar in the Everglades have a narrow diet breadth (Loftus, 2000) feeding on other fish, amphibians, grass shrimp, and crayfish. Gar can move long distances (Snedden et al, 1999) and tracking studies in the Everglades have shown Florida gar to travel 5 km or more in one day when water levels drop locally in the dry season (Wolski & Trexler, unpublished data). However, in the wet season when our isotopic data were gathered, most radiotagged gar moved relatively little, displaying nighttime foraging movements from depressions and ponds and returning to the same area each day.…”

Turbidity reduces hatching success in Threatened Spotted Gar (Lepisosteus oculatus)

“…Spawning takes place in waters ranging from 20 to 30°C (Echelle and Riggs 1972), and movement of adults into floodplains and inundated riparian areas is initiated at approx. 15°C in Louisiana (Snedden et al 1999). Similarly, in Rondeau Bay, Lake Erie movement to spawning areas (vegetated wetlands and inundated riparian zones, 0-1 m deep) occurs at approx.…”