Responses of Anadromous Salmonids to Habitat Modification: How Do We Measure Them?
Fisheries Bioengineering Symposium: American Fisheries Society Symposium 10
Colt J;White RJ;
American Fisheries Society
Responses of anadromous fish populations to habitat manipulations are seldom measured. The primary reasons given for this neglect are inadequate funds, personnel, and time. This paper examines ways in which biological responses to habitat manipulation can be evaluated at different stages in the life history of anadromous salmonids. Responses that can be measured are changes in numbers of adult fish, changes in numbers of juvenile fish, and changes in numbers of smolts leaving a stream or stream system. The authors assess the merits of each approach and conclude that changes in smolt numbers are the best way to evaluate the effect of habitat manipulation projects on anadromous salmonid populations. Evaluation programs should be developed on a basin or subbasin scale because reach or site scales provide an inadequate context for evaluating change. Evaluations should also consider the response of the entire salmonid community to changes in habitat rather than the response of a single or target species.