Introduction of Kokanee Salmon (Oncorhynchus nerka) into Lake Huron

Abstract

An experimental introduction of kokanee salmon (Oncorhynchus nerka) into Lake Huron from egg stocks obtained from British Columbia and several western states of the United States began in 1964. From 1964 to 1969, about 5.5 million kokanee (eggs, fry, and fingerlings) were planted. Estimated minimum returns of adults were 9000, 1200, and 4000 in 1967, 1968, and 1969, respectively. Although most of the returns were recorded near planting sites, substantial numbers moved into other areas, in some instances spawning in streams that were not planted. Apparently, most kokanee matured in their 3rd year of life (2+) and their lengths ranged from 18 to 49 cm.The incidence of lamprey marks on adults was light (1.6% of 4472 examined) but frequencies of marks tended to increase as fish size increased — from 0.5% for 28–32 cm fish to 16.7% for fish over 40 cm long.Successful stream spawning in 1967 was indicated by the retrieval of live eggs and alevins from redds and the capture of downstream migrant fry. Shore spawning was verified by retrieval of viable eggs from redds in 1969. The potential egg deposition in the two rivers with the largest runs in 1967 was approximately 2.7 million eggs. Fish from British Columbia river-spawning stock spawned both in streams and along shores of South Bay. Since spawning was not restricted to streams, the shore areas of Lake Huron may extend the spawning habitat available to kokanee.Adult kokanee fed mainly on insects and plankton during August and September. Aerial forms of insects predominated in South Bay kokanee. Dieldrin and DDT residues were moderate, averaging between 0.012 and 0.046 ppm for dieldrin and 0.226 and 1.242 ppm for DDT in whole tissue samples.Data from South Bay show that the principal species found in association with kokanee were alewife and smelt. The diet of alewife in August indicated possible competition with kokanee.