Induction of precocious maturation in masculinized Atlantic salmon by treatment with sustained-release LHRHa and testosterone

The effect of treating immature, masculinized, Atlantic salmon, Salmo salar , with testosterone or [Des-Gly(10)] D-Ala(6)-LHRH ethylamide (LHRHa), eith er alone or in combination, over an 81 day period was evaluated as a method for accelerating maturation. Two sustained-release LHRHa implants were com pared: ethylene vinyl acetate copolymer (EVAC) and silicone elastomer. Anim als primed with testosterone did not express advanced spermatogenesis when compared against control salmon (p > 0.05). However, fish primed with testo sterone, followed by sham, LHRHa EVAC, or LHRHa silicone elastomer implants expressed increased (p < 0.05) gonadosomatic index (GSI) when compared wit h values derived from day 0 of the study. Neither spermatogenesis nor CSI w ere affected when salmon were treated with LHRHa alone, irrespective of the vehicle employed. In contrast, spermatogenesis was significantly (p < 0.05 ) advanced in testosterone-treated fish, which were administered LHRHa by E VAC, when compared with groups that received individual treatment only.