Hydrologic Effects on Growth and Hatching Success of Age-0 Channel Catfish in the Tallapoosa River Basin: Implications for Management in Regulated Systems

We assessed the effects of hydrology on growth and hatching success of age-0 Channel Catfish Ictalurus punctatus in regulated and unregulated reaches of the Tallapoosa River basin, Alabama. Age-0 Channel Catfish (N = 91) were collected from sites in both the Coastal Plain and Piedmont regions in fall 2003 and fall 2005. Lapillus otoliths were used to estimate the daily ages of age-0 Channel Catfish, for which hatch dates were back-calculated. We performed growth analysis to determine growth histories of each fish at 20-d increments from hatch. Across the 2 years of sampling, Channel Catfish hatches were documented from June 7 to September 15. Ages and growth rates of age-0 Channel Catfish ranged from 20 to 126 d and 0.60 to 1.5 mm/d, respectively. In general, growth was highest among age-0 Channel Catfish from unregulated sites in the lower Coastal Plain, lowest among fish from unregulated sites in the Piedmont, and intermediate from regulated sites in the Piedmont. Successful hatching typically occurred during periods when mean discharges were in the upper two quartiles of flows for each site but not during exceptionally high peaks in flow. Physiographic province, the frequency of high pulses, and the number of flow reversals were the most important factors influencing the growth of recently hatched Channel Catfish. Results suggest that a low to moderate frequency of high pulses (25-150 pulses per 20-d increment) and a moderate number of flow reversals (similar to 100-175 reversals per 20-d increment) enhances early growth of Channel Catfish in the Tallapoosa River system. Managing flow, when possible, to minimize large releases of water that result in exceptionally high pulses and providing minimal hydropeaking may improve hatching success during the Channel Catfish spawning season.