The lake charr Salvelinus namaycush is a ubiquitous member of cold-water lake ecosystems in previously glaciated regions of northern continental U.S., Alaska, and Canada that often support important commercial, recreational, and subsistence fisheries. The lake charr differs from other charrs by its large size, longevity, iteroparity, top-predator specialization, reduced sexual dimorphism, prevalence of lacustrine spawning, and use of deepwater habitat. The species is remarkably variable in phenotype, physiology, and life history, some of which is reflected in its ecology and genetics, with as many as four morphs or ecotypes co-occurring in a single lake. The lake charr is often the top predator in these systems, but is highly adaptable trophically, and is frequently planktivorous in small lakes. The lake charr by their name highlights their common habitat, lakes both large and small, but often frequents rivers and occasionally moves into the Arctic Ocean. Movement and behaviour of lake charr are motivated by access to cool, well-oxygenated water, foraging opportunities, predator avoidance, and reproduction. Owing to their broad distribution and trophic level, the lake charr serves as a sentinel of anthropogenic change. This volume will provide an up-to-date summary of what is currently known about lake charr from distribution to genetics to physiology to ecology. The book provides a compilation and synthesis of available information on the lake charr, beginning with an updated distribution and a revised treatment of the paleoecology of the species. Understanding of ecological and genetic diversity and movement and behaviour of the species has advanced remarkably since the last major synthesis on the species over 40 years ago. Mid-sections of the book provide detailed accounts of the biology and life history of the species, and later sections are devoted to threats to conservation and fishery management practices used to ensure sustainability. A new standard lake charr-specific terminology is also presented. The book will be a valuable reference text for biologists around the world, ecologists, and fishery managers, and of interest to the angling public.

Abstract : It has been frequently reported that concentrations of PCBs in the Great Lakes fish have declined dramatically since their ban on production and use in 1979 in the United States, although some studies suggested that recent rates of decline are leveling off. In order to examine the temporal trends and spatial variabilities of PCB concentrations in lake trout (Salvelinus namaycush) from Lake Superior during the past two decades, statistical analyses were performed on fish sample data collected by two national agencies (U.S. EPA, Environment and Climate Change Canada) and three state agencies (Michigan Department of Environmental Quality, Minnesota Department of Natural Resources, Wisconsin Department of Natural Resources) from both the United States and Canada from 1976 to 2013. Because of a change in PCB analytical methodology in the mid-1990s, intercomparison between data recorded by the previous technique and the improved technique is not feasible. Because most organochlorine compounds are easily bound to fatty tissues in fish, lipid content has been commonly considered as a predictor of PCB levels. Also, larger fish were assumed to have higher PCBs in their bodies. Multiple linear regression analyses, setting time, lipid content, and fish length as three independent variables, revealed that lipid content had little impact on PCB concentrations at all sites except Whitefish Bay since 1995, which is in contrast to some previous studies. However, a strong positive correlation between PCBs and fish length, in good agreement with previous research, was observed at all sites except Whitefish Bay over the same period. It has been discovered that PCB concentrations vary among several sampling locations within Lake Superior. The general pattern was that the western sites had significantly higher concentrations than the eastern sites. When the entire historical record was analyzed, temporal trends were evident in all datasets. However, only at Keweenaw Point (U.S. EPA) was significant (p = 0.0005) declining trends in total PCB concentrations observed after 1995. In Wisconsin sites, the declining trend was marginal significant (p = 0.04) during the same period. In other locations, no temporal trends were found but large annual fluctuations occurred for unknown reasons. PCB concentrations at most sites have not achieved the reduction target of 100 ng/g ww for wildlife and human health protection established by the U.S. EPA. It is still difficult to predict when fish will be able to be consumed without limitation in this region.