White Crappie ( Pomoxis annularis ) latency period following hormone administration is predictable and independent of diel injection time

Abstract

Relatively little is known of the effects of time of day of hormone injection on latency period in most fishes. Interest in improved culture techniques for White Crappie (Pomoxis annularis) has led to advances in tank holding and induced spawning methods. However, an understanding of latency period is needed for synchronizing and optimizing White Crappie hatchery production. Therefore, the effects of hormone injection timing on latency period and egg viability were examined. Crappie were injected with gonadotropin-releasing hormone analog (GnRHa) at 1600 (evening treatment) and 0800 (morning treatment), monitored for latency period duration, and spawning success was determined using percent of females ovulated, ovulated egg volume and egg fertilization percent. In the evening treatment group, 75% of the females ovulated 48.40 ± 2.70 (mean ±SE) hours post initial injection and had a mean egg fertilization rate of 63%, while in the morning injection treatment, 91% of females ovulated 44.58 ± 1.36 h post initial injection and had a mean fertilization rate of 56%. No significant difference in mean latency period or spawning success was observed between treatments. Therefore, diel timing of hormone injection did not affect latency period or spawning success in White Crappie, allowing for flexibility in production.