A Comparison of Two Methods of Rearing and Stocking Coho Salmon in Wisconsin's Waters of Lake Michigan

Abstract

Since 1968, the Wisconsin Department of Natural Resources has stocked coho salmon Oncorhynchus kisutch in Lake Michigan as spring yearlings (14–16 months old) and as accelerated-growth fall fingerlings (9 months old). We compared accelerated-growth with spring yearling groups to evaluate (1) return rates of jacks and adults to spawning weirs and to the sport fishery, (2) growth rates, and (3) cost–benefit ratios. Returns to spawning weirs and Wisconsin anglers showed similar patterns. Return rates of jacks were similar for fish stocked as fingerlings and yearlings and were higher in the Root River than in the Kewaunee River for both stocking strategies. The weir and angler rates for adults were higher for fish stocked as yearlings than as fingerlings and were higher in the Root River than in the Kewaunee River for both stocking strategies. Estimated return rates of adults to Wisconsin anglers ranged from 0.0% to 5.4% for fish stocked as fingerlings and from 0.1% to 15.6% for fish stocked as yearlings. Estimated return rates of adults to the weirs ranged from 0.5% to 4.4% for fish stocked as fingerlings and from 0.4% to 11.0% for fish stocked as yearlings. For two year-classes, adult coho salmon stocked as yearlings were found to be significantly longer and heavier than adults of the accelerated-growth group at time of return. Despite higher noncapital costs to produce yearlings ($0.409) than fingerlings ($0.235), the higher return rates of the yearling group resulted in lower costs per returning fish at weirs ($6.84 for yearlings versus $8.27 for accelerated-growth fingerlings) and to anglers ($9.28 for yearlings versus $11.03 for accelerated-growth fingerlings).