By Robert John Gibson
A short review is presented on the major factors contributing to recent precipitous declines in populations of wild Atlantic Salmon Salmo salar, with the approach of describing the major needs for stabilizing or enhancing factors to conserve and reverse the decline of salmon populations and incidentally of other salmonid species. Some aspects of physiology and required habitat characteristics through the life history of Atlantic Salmon are reviewed that determine responses to degradation of habitats.
A conservation plan must address the effects of perturbations within the watershed, such as logging, road building, loss of riparian vegetation, and hydroelectric dams that would change the hydrological regime with coincidental changes in sedimentation rate, such as effects of imbedding (typically upstream of the dam) or, alternatively, loss of finer materials (downstream of the dam) such as spawning gravels, which are not replaced downstream due to the dam (“armoring” of the stream bed), or encroachment of vegetation, depending on the circumstances
Anthropogenic developments, including obstructions to migration and degradation of freshwater habitats, are major reasons for declines in the resource. Thus, habitat is a primary factor to be considered in conservation and restoration. Socioeconomic considerations may override ecological and public interest concerns, and examples are given from Canada, where environmental regulations have been relaxed in favor of economic interests. Public education and awareness and advocacy in order for political “will” for better conservation of the resource are required to slow, and eventually stop, the decline in Atlantic Salmon populations.
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