Reproduction and culture of suckermouth minnow

Introduction of captively reared suckermouth minnow Phenacobius mirabilis into Colorado streams where they are rare or extirpated may be a viable technique to enhance the status of this state-endangered species, but information on reproductive ecology and culture techniques is lacking. We successfully spawned suckermouth minnow in the laboratory by using hormone injections, observed reproductive behavior, and reared larvae to juvenile size in aquaria. Suckermouth minnow spawned over interstitial spaces in gravel and cobble substrate in water temperatures of 17, 19, and 23 degrees C after injections of chorionic gonadotropin (males) and carp pituitary (females). Groups of several fish were involved in spawning, which occurred nearly continuously for several hours after the fish were placed in aquaria; typically, only one or a few eggs were released in any single spawning bout. Viable, adhesive eggs were found on gravel and cobble substrate but not on sand or other attachment surfaces in aquaria. Only suckermouth minnow that were in peak reproductive condition successfully spawned after hormone injections. Voluntary spawning also occurred in the absence of hormone injections. We observed potential cannibalism of suckermouth minnow eggs immediately after spawning, suggesting that isolation of embryos or adults after spawning may be necessary for successful culture. Suckermouth minnow were stripped of gametes, and embryos were successfully reared to hatching at temperatures of 17, 19, and 23 degrees C; rearing was most successful at 17 degrees C and 23 degrees C. The development and growth of larvae (4.2-4.8 mm total length at hatching) was faster at 23 degrees C (mean = 0.57 mm/d) than at 17 degrees C and 19 degrees C (0.35 mm/d). The slow initial growth of larvae may be due to food that was of inappropriate size or low quality. Raising suckermouth minnow in captivity may be a useful conservation tool to establish populations in suitable habitat.