Environmental impact research program: Use of field techniques to assess the environmental effects of commercial navigation traffic
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Recently completed navigation projects in the United States were responsible for directing the attention of conservation agencies to the impacts of commercial vessel movement. It was suggested that vessel-induced change in magnitude and direction of flow could negatively affect growth, reproduction, and survival of benthic organisms. Laboratory studies demonstrated that mortality or physiological stress to fish larvae or freshwater mussels (family: Unionidae) can be measured under conditions corresponding to high traffic intensity. However, it is difficult to estimate an organismal response to intermittent physical effects, and it is even more difficult to accurately predict long-term responses of natural populations to such disturbances. The biological consequences of commercial vessel passage should be measured on populations of species in their natural habitats. Studies should provide quantitative data on biotic parameters such as density, relative species abundance, community composition, population demography, and rate of growth. Adequate baseline data should be collected; then, additional studies should be conducted to determine whether commercial vessel movement causes measurable change to naturally occurring populations and communities.