INTERACTION OF ABIOTIC AND BIOTIC FACTORS INFLUENCES LARVAL FISH SURVIVAL IN AN OKLAHOMA STREAM

Both abiotic and biotic factors affected larval fish in Baron Fork, Oklahoma. Nighttime drift rates were very high (up to 31 larvae/m3) during normal flow. Censuses indicated that daytime abundances of larvae occupying pools were influenced significantly by the presence of juvenile and adult smallmouth bass (Micropterus dolomieui). Minnow larvae were less abundant in pools occupied by juvenile smallmouth bass and more abundant in pools with adult smallmouth bass. Experimental manipulation of adult bass supported the hypothesis that their presence benefits the larvae of other species, but pool type influenced this response. Differences between the effects of adult bass on the accumulation of larvae in main channel pools compared with side pools appeared to reflect the influence of drift. The benefit that adult bass provided the larvae of other species probably involved their impacts on juvenile bass and other small fishes, which may be the most significant predators of larval fish. The pattern of co-occurrence between adult bass and the larvae of other species in Baron Fork parallels results from lakes and smaller streams.