Geology topics

Wayne R. MacCallum

Publications and source records attributed to Wayne R. MacCallum.

3 recordsLinked to original sources

USGS1995

Lake trout ( Salvelinus namaycush ) populations in Lake Superior and their restoration in 1959-1993

Naturally-reproducing populations of lake trout ( Salvelinus namaycush ) have been reestablished in most of Lake Superior, but have not been restored to 1929-1943 average abundance. Progress toward lake trout restoration in Lake Superior is described, management actions are reviewed, and the effectiveness of those actions is evaluated; especially stocking lake trout as a tool for building spawning stocks, and subsequently, populations of wild recruits. Widespread destruction of lake trout stocks in the 1950s due to an intense fishery and sea lamprey ( Petromyzon marinus ) predation resulted in lower overall phenotypic diversity than was previously present. Stocking of yearling lake trout, begun in the 1950s, produced high densities of spawners that reproduced wherever inshore spawning habitat was widespread. Sea lampreys were greatly reduced, beginning in 1961, using selective chemical toxicants and barrier dams, but continue to exert substantial mortality. Fishery regulation was least effective in Wisconsin, where excessive gillnet effort caused high by-catch of lake trout until 1991, and in eastern Michigan, where lake trout restoration was deferred in favor of a tribal fishery for lake whitefish ( Coregonus clupeaformis ) in 1985. Restoration of stocks was quicker in offshore areas where remnant wild lake trout survived and fishing intensity was low, and was slower in inshore areas where stocked lake trout reproduced successfully and fishing intensity was high. Inshore stocks of wild lake trout are currently about 61 % of historic abundance in Michigan and 53% in Wisconsin. Direct comparison of modern and historic abundances of inshore lake trout stocks in Minnesota and Ontario is impossible due to lack of historic stock assessment data. Stocks in Minnesota are less abundant at present than in Michigan or Wisconsin, and stocks in Ontario are similar to those in Michigan. Further progress in stock recovery can only be achieved if sea lampreys are depressed and if fisheries are constrained further than at present.

Journal of Great Lakes Research↗

USGS1995

Genetic strategies for lake trout rehabilitation: a synthesis

The goal of lake trout rehabilitation efforts in the Great Lakes has been to reestablish inshore lake trout ( Salvelinus namaycush ) populations to self-sustaining levels. A combination of sea lamprey control, stocking of hatchery-reared lake trout, and catch restrictions were used to enhance remnant lake trout stocks in Lake Superior and reestablish lake trout in Lakes Michigan, Huron, Erie, and Ontario. Genetic diversity is important for the evolution and maintenance of successful adaptive strategies critical to population restoration. The loss of genetic diversity among wild lake trout stocks in the Great Lakes imposes a severe constraint on lake trout rehabilitation. The objective of this synthesis is to address whether the particular strain used for stocking combined with the choice of stocking location affects the success or failure of lake trout rehabilitation. Poor survival, low juvenile recruitment, and inefficient habitat use are three biological impediments to lake trout rehabilitation that can be influenced by genetic traits. Evidence supports the hypothesis that the choices of appropriate lake trout strain and stocking locations enhance the survival of lake trout stocked into the Great Lakes. Genetic strategies proposed for lake trout rehabilitation include conservation of genetic diversity in remnant stocks, matching of strains with target environments, stocking a greater variety of lake trout phenotypes, and rehabilitation of diversity at all trophic levels.

Journal of Great Lakes Research↗

USGS1994

Rainbow smelt - larval lake herring interactions: competitors or casual acquaintances?

We examined the hypothesis that competition for food between rainbow smelt (Osmerus mordax) and larval lake herring (Coregonus artedi) was a cause for the declines of lake herring stocks in Lake Superior. We studied the diet of larval lake herring and of larval, juvenile, and adult rainbow smelt during 1974 in Black Bay, Ontario, where both species were abundant, and in the Apostle Islands Region, Wisconsin, where rainbow smelt was abundant but lake herring was scarce. No evidence of competition for food was found between larval lake herring and rainbow smelt. Spawning and hatching times of the two species were separate enough that most larvae of the two species did not occupy the study areas simultaneously. Juvenile and adult rainbow smelt were found with lake herring larvae, but their diets differed. Therefore, we concluded that rainbow smelt did not compete with lake herring larvae for food and that competition for food between rainbow smelt and lake herring larvae was not the factor that caused lake herring population declines in Lake Superior.

Biological Report↗