Population characteristics and potential factors influencing recruitment variability of blue catfish, channel catfish and flathead catfish in Thunderbird Reservoir, Oklahoma

Abstract Blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus) and flathead catfish (Pylodictis olivaris) are popular sport fishes throughout North America, and are therefore intensively managed by some natural resource agencies. Although catfish fisheries rely on sufficient natural reproduction and recruitment to sustain these populations, few studies have evaluated the variables affecting catfish recruitment. Thus, the objectives of this study were to describe population characteristics (age, size structure, condition, growth, mortality and recruitment) of blue catfish, channel catfish and flathead catfish in Thunderbird Reservoir, Oklahoma, and evaluate the effects of hydrology, water quality and temperature on year‐class strength. During 2017 and 2018, 235 blue catfish, 194 channel catfish and 120 flathead catfish were collected and aged using otoliths. In general, these catfish species in Thunderbird Reservoir were slow growing, long‐lived, had low mortality rates and experienced variable recruitment. Blue catfish recruitment was lower in years with higher average January air temperatures. Channel catfish recruitment was higher in years with increased average annual and spring/summer exchange rate and increased spring/summer average reservoir water volume (ha‐m). Conversely, higher annual average total hardness (mg/L) resulted in decreased recruitment for channel catfish. Flathead catfish recruitment exhibited a minimal negative impact with increased annual reservoir volume (ha‐m). The present study is among the first to describe potential variables influencing year‐class formation of blue catfish, channel catfish and flathead catfish in reservoirs. Although the variables found to influence catfish recruitment are outside the control of fisheries managers, biologists should promote downstream angling opportunities for blue catfish that escape during reservoir water release events and stock channel catfish in systems with consistently high total water hardness in order to maximize fishing opportunities. Further, they can use the results of this study to manage angler expectations following periods of low recruitment.