Genetic and Ecological Guidelines for Species Reintroduction Programs: Application to Great Lakes Fishes

Abstract

Complete restoration of the Great Lakes is unlikely, due to naturalization of exotic species, habitat degradation and destruction, heavy fishing mortality, lack of native gene pools, and complicated political jurisdictions that rarely work toward a common vision. A more realistic goal is rehabilitation, a movement along the trajectory toward complete restoration. Proper rehabilitation employs an evolutionary-genetic perspective, which protects and works with the remaining genetic variation available in lake trout or other species of concern. A difficult question is how to define the units of genetic conservation; one answer is to determine Evolutionary Significant Units. To do this, population structure must be defined, and various conceptual models are here presented that determine genetic population structure as a function of geographic structure of the habitat. Several concepts from the developing field of conservation biology should also be incorporated into lake trout rehabilitation. These include metapopulations—groups of populations that experience some degree of regular or intermittent gene flow, and that serve as recolonization sources after local extinctions. Related to this is “source-sink dynamics,” a recognition that habitats typically are unequal in quality. Habitat fragmentation is also relevant because it can stop inter-population movement and disrupt metapopulation structure and source-sink dynamics. Finally, hatcheries should be used in rehabilitation only with great caution and skepticism. Hatcheries tend to address the symptoms, rather than the causes, of fish declines, and may mask the underlying problems by continually replacing declining fish. Improved habitat quality, rather than artificial production, is the key to rehabilitation of the Great Lakes for lake trout and other native species, and hatcheries should only be used as a stopgap measure to prevent further losses of genetic diversity.