Effects of prolonged prespawn holding on spawning efficiency of wild White Crappie

Objective Crappie Pomoxis spp., belonging to the family Centrarchidae, are among the most sought-after sport fish species in the United States. Crappie spawn during early spring in response to increasing photoperiod and water temperature, meaning that hatchery operators have limited time to capture and spawn broodstock. The ability to hold crappie for an extended time under prespawn conditions would allow for flexibility in scheduling spawning activities; however, the effects of prolonged holding on spawning efficiency and egg quality are not well understood. Methods Two studies were conducted to determine the effects of holding time under extended prespawn conditions (temperature = 13–15°C) on the spawning efficiency of prespawn White Crappie P. annularis. Crappie were held in 5,000-L recirculating aquaculture systems for 6 and 8 weeks in year 1 (2023) and for 4 and 8 weeks in year 2 (2024), with 8 weeks chosen to coincide with the maximum duration of hatchery stocking practices. After holding in the 5,000-L tanks, broodstock were moved to smaller (450-L) tanks, where they were held for 2 weeks before spawning was induced by epaxial intramuscular injections of gonadotropin-releasing hormone analog (a 10% priming dose and then a 90% resolving dose 24 h later). Fish were strip-spawned upon ovulation. Results In year 1, 49% of females in the 6-week group ovulated, with a 54% fertilization rate; 47% of females in the 8-week group ovulated, with a significantly lower 12% fertilization rate. In year 2, 81% of females in the 4-week group ovulated, with a 52% fertilization rate; 93% of females in the 8-week group ovulated, with an 11% fertilization rate. Conclusions This study provides new insights into the extended holding potential and associated limitations for White Crappie spawning. Since key reproductive metrics, such as fecundity, remained stable over time, wild White Crappie broodstock can be maintained under prespawning conditions in recirculating aquaculture systems for up to 8 weeks. However, to maximize egg fertilization rates, the holding duration should be limited to 6 weeks.