Acceleration of Sexual Maturation in Chinook Salmon Broodstock Using Luteinizing Hormone-Releasing Hormone Analog

Abstract

In response to problems encountered in broodstock acquisition and egg collection at Homer Spit, Alaska, we tested the effectiveness of a luteinizing hormone-releasing hormone analog (LHRHa) in accelerating and synchronizing the sexual maturation of chinook salmon Oncorhynchus tshawytscha. We captured 341 fish in salt water and transported them to Elmendorf Hatchery in Anchorage, Alaska, where we injected 170 fish with 25 μg LHRHa/kg and held them until spawning. Significantly (P = 0.003) more LHRHa-treated chinook salmon spawned, and they spawned within 17 d of capture, whereas fewer control salmon spawned even within 38 d of capture. Hormone-analog-treated males also produced significantly (P < 0.001) more milt with a greater percentage of motile sperm than did control males. Hormone-analog-treated females, however, had significantly (P = 0.007) lower fecundity and smaller eggs than control females. Eggs from LHRHa-treated fish also had significantly (P < 0.001) greater eyed egg and alevin mortality. Although the LHRHa treatments were successful in accelerating and synchronizing spawning time, treated chinook salmon produced fewer offspring than the untreated fish did. In this study, the advantages conferred by hormone treatments were not sufficient to overcome the increased mortality of eggs and alevins.