Growth in stream-stocked juvenile hatchery-reared coastal cutthroat trout (Oncorhynchus clarki clarki) and the implications for wild populations

Abstract

Abstract Growth in young of the year (YOY) anadromous coastal cutthroat trout was compared between fry-reared for the first year in a hatchery (YOY-H) and fry-stocked (YOY-M) into a small coastal British Columbia stream. Results found the hatchery-reared fish were significantly larger in both length (148%) and weight (336%) after a 323-day period when compared to the group allowed to rear in the stream. In the second year of captive rearing, yearling cutthroat trout were selected from the hatchery-reared (YEAR-H) YOY group and stocked into the stream when they were 124% larger in length than the comparable stream-reared yearlings (YEAR-W). At 298 days post-stocking, the YEAR-H fish had lost their initial size advantage and the YEAR-W fish were 126% larger in length and 143% larger in weight. In hatchery presmolts, early maturation was found to be accelerated in hatchery-reared fish with study groups (92BY and 93BY-A) showing high percentages (30–45%) of early maturation compared to stream-reared presmolts (93BY-B). These significant differences in rearing performance between hatchery-stocked and stream-reared juvenile cutthroat trout may influence survival and fitness of the naturally reared juvenile cutthroat trout.