Advances in Fisheries Bioengineering

Light Tags for Observing Behavior of Surface-Oriented Migrating Salmonids

Mark S. Bevelhimer and Charles C. Coutant


Abstract.— The bioengineering field needs an inexpensive tool to monitor fish behavior in relation to structures and hydraulic features at hydropower and thermoelectric power plants. We attached inexpensive chemiluminescent light sticks to 243 yearling steelhead Oncorhynchus mykiss to assess the feasibility of using light emitting tags as an inexpensive method to observe night time movements of downstream-migrating steelhead at a hydropower dam powerhouse and headrace. Adaptation of a small monofilament T-bar anchor tag allowed rapid tagging with minimal handling stress. Preliminary studies in the laboratory indicated no apparent deleterious effects of the tags. The near-neutrally buoyant, 37 × 4 mm light sticks were held about 2 cm above the fish’s back and were visible from all directions. Visual observations allowed definition of trajectories of 138 fish from point of release in relation to several physical structures and hydraulic patterns near a hydropower dam. Less detailed observations were made for another 40 fish. The technique was valuable for obtaining detailed movement patterns of fish at depths up to about 1.7 m and over areas of about 30 m radius from one observer located about 3 m above the water surface. The main use for light tags is likely to be for short-duration, night observations of fish behavior in small streams, for shallow near-shore areas, or with surface-oriented fish. The technique seems useful for observing fine-scale fish movements near physical and hydraulic features associated with shallow entrances to water intakes, such as for turbines or fish bypasses. Additional observers and/or video surveillance can extend the distance of observations, the accuracy of the data, and quantification of results.