Phenotypic Comparisons among Natural‐Origin, Hatchery‐Origin, and Captive‐Reared Female Spring Chinook Salmon from the Tucannon River, Washington

Abstract

AbstractWe examined the effects of hatchery rearing on FL, weight, egg size, fecundity, relative fecundity, and reproductive mass of female spring Chinook Salmon Oncorhynchus tshawytscha from a population that had been in captivity for 0 (natural‐origin), 18 (hatchery‐origin), and 48 (captive‐reared broodstock) months. Age‐4 captive‐reared broodstock females that were reared for their entire life in the hatchery environment had significantly lower mean FL, weight, fecundity, relative fecundity, and reproductive mass, but had significantly larger eggs than age‐4 females from the other groups after correcting for body size. Hatchery‐origin females had significantly lower fecundity than natural‐origin fish. Our findings illustrate a phenomenon of lower overall reproductive potential for hatchery‐reared fish in the form of reduced fecundity that decreases as time spent in the hatchery environment increases. We also observed that progeny of captive‐reared broodstock parents, released as smolts and recaptured as returning age‐4 adults, have a size and fecundity distribution that is similar to the hatchery‐origin adults, suggesting that the decrease in fecundity was not a genetically linked trait.