Gregory L. Looney, Warm Springs Fish Technology Center, 5151 Spring Street, Warm Springs, GA 31830; Timothy A. Barrett, Georgia Dept. Of Natural Resources, Wildlife Resources Division - Fisheries, Route #2 Box 219R, Richmond Hill, GA 31324; James L. Shelton, Jr. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602

Abstract. The study objectives were to evaluate the efficacy of hormone induced ovulation of female robust redhorse, Moxostoma robustum. The robust redhorse (RRH) is a large (maximum size about 760 mm TL) catostomid that was re-discovered in the Oconee River, GA, on 8 August 1991, near the mouth of Commissioner Creek. Estimated population size is 1,000 - 3,000 individuals, most of which are quite old (10 - 26 years). There has been no evidence of substantial recruitment in the past ten years. A temporary spawning facility was constructed adjacent to the bank of the Oconee River, Georgia. This site was chosen due to is proximity to known spawning aggregations of RRH and its secure boat launching facility. The brood fish holding and spawning system consisted of nine to twelve 1,800-L circular tanks, one to two 115 L anesthesia tanks, a 1-1/2 horse power water pump, a 1/4 horse power air blower, and one or more gasoline powered generators. Females were stocked at a rate of 3-5 individuals per tank and males were stocked at a higher density of 5-10 individuals per tank due to limited tank space. Due to the large size of this fish and the need to minimize stress during handling, an anesthetic (Metomidate) was administered prior to physical examinations and spawning. In 1995, five hormone treatment regimes were evaluated; Carp Pituitary Extract (CPE), Human Chorionic Gonadotropin (HCG), CPE plus a resolving dose of HCG, an analog of Luteinizing Hormone - Releasing Hormone (LH-RHa), and OvaprimŽ. A sterile saline solution was used as the control. The three hormone treatment regimes found to be most effective in 1995 (OvaprimŽ, HCG, CPE) were re-evaluated in 1996, comparing them to the same control used in 1995. Of the 21 females used in the study in 1995 (4 with OvaprimŽ, 3 with CPE, 3 with HCG, 4 with LH-RHa and 3 with the combination of CPE and HCG), all of the females in the OvaprimŽ treatment spawned, 2 of the CPE females spawned, 2 of the HCG females spawned, none of the LH-RHa females spawned, and 1 of the females in the combination spawned. Of the 17 females in the study in 1996 (4 with OvaprimŽ, 5 with CPE, and 4 with HCG) all of the females in the OvaprimŽ treatment spawned, none of the CPE females spawned and 1 of the HCG females spawned. None of the fish in the 1995 or 1996 control treatments spawned.