QUENTON FONTENOT AND D. ALLEN RUTHERFORD, School of Forestry, Wildlife, and Fisheries, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803, USA

The Atchafalaya River Basin (ARB) is inundated each year by a spring flood pulse
(~ 2 m). Increasing temperatures and river stage create large areas of water with dissolved oxygen concentrations < 20% saturation (hypoxia) during the spawning season of many fishes (May - July). Environmental hypoxia could significantly reduce survival of individual larvae and affect overall fish production of the entire ARB. The principle objective of this study was to determine if naturally occurring hypoxia was related to the abundance patterns of larval fishes of the ARB. Chi square analysis of presence-absence data indicated that Lepomis spp. (P < 0.672) and Dorosoma spp. (P < 0.236) were common in both hypoxic and normoxic water. Presence absence data on the following taxa show they were obviously more common in normoxic than hypoxic water: catastomids (10 to 0), cyprinids (8 to 0), ictalurids (13 to 0), and sciaenids (15 to 1). Also, when Lepomis spp. and Dorosoma spp. are included with all other taxa, chi square analysis indicate overall, larval fishes are not as common in hypoxic as in normoxic water (P < 0.001). We feel these data suggest that hypoxia in the ARB is limiting overall fish production.