The Topeka shiner (Notropis topeka) is an endangered freshwater fish species that is native to shallow, clear streams and rivers in the central United States. Due to declining populations, there is an urgent need for innovative conservation strategies. This study explores hormonal induction techniques for spawning Topeka shiners to improve controlled breeding programs and aid in population recovery efforts.
The research aimed to characterize latency periods, test egg deadhesion methods, measure fertilization rates, and optimize dosing protocols for spawning success. Using intraperitoneal injections, we administered 50 µl of carp pituitary extract (CPE) at a dosage of 2 mg/ml or human chorionic gonadotropin (hCG) at a dosage of 500 IU/kg to mature 13-month-old male and female broodstock (Fig. 1). Fish were from a captive population maintained at the USGS Columbia Environmental Research Center, Missouri. Eggs get adhesive quickly, so Fullers earth (15 g/L), tannic acid (400 mg/L) and sodium sulfite (15 g/L) were tested for deadhesion effectiveness.
A dosage of 50 µl of 2 mg/ml CPE per fish was effective at inducing ovulation and spermiation. Latency periods for CPE varied from 8 to 10.5 hours after injection. All deadhesion methods were effective, but sodium sulfite was fast acting and allowed visibility of egg development. Findings for hCG and fertilization rates will also be presented. This research underscores the potential of artificial spawning to bolster Topeka shiner populations, support habitat restoration efforts, and enhance genetic diversity within threatened populations. Future research could prioritize the long-term survival rates of hatchlings and the incorporation of artificial spawning practices into comprehensive conservation plans.