Efficacy of Varying Doses of Cgnrh IIa on Spawning Performance of Pinfish and Pigfish

Pinfish,Lagodon rhomboides, and pigfish,Orthopristis chrysoptera, are popular marine baitifsh used throughout the southeastern United States. Well-defined methods exist for closing their life cycles in captivity and are being used for commercial aquaculture efforts for each species. Multiple spawning hormones have been effective for spawning induction for both species. Evaluations of a type II gonadotropin-releasing hormone (cGnRH IIa) have proven it effective for induced spawning in channel catfish, and it has been proposed to be an effective hormone for induced spawning in other species. Four dosages (25, 50, 100 and 200 mu g/kg) of cGnRH IIa for spawning induction along with a negative (saline at 0.5 ml/kg) and positive control (Ovaprim (R) at 0.5 ml/kg) treatment were evaluated for both species. Pinfish and pigfish responded to every cGnRH IIa tested, with up to nine viable spawns collected from pigfish at 100 mu g/kg and up to five viable spawns collected from pinfish at 200 mu g/kg. The amount of sinking eggs spawned, egg and larval size, and hatching success and survival to first feeding differed significantly for pigfish. Total egg production, fecundity, egg and larval size, and hatching success and survival to first feeding were significantly different for pinfish. While effective for spawning induction in both species, there may be some decrease in spawn quality associated with cGnRH IIa, at least for pigfish. Future research directed towards understanding the potency and physiological reactions caused by cGnRH IIa will help corroborate findings of higher egg output and reduced egg and larval quality.