Simulated instream restoration structures offer smallmouth bass (Micropterus dolomieu) swimming and energetic advantages at high flow velocities

Restoration practices aimed at fish habitat enhancement often include installation of instream structures. However, mixed outcomes have been reported regarding structure effectiveness, while mechanisms underlying success remain unclear. The interactions between fish and flow conditions generated by instream structures and their subsequent impact on fish energetics may provide some insight. This study seeks to quantify how restoration structures, simulated by cylinders in three orientations, alter the energetics and swimming stability of smallmouth bass (Micropterus dolomieu). Accelerometers measured swimming stability while a respirometer measured energy expenditure at multiple velocities. Particle image velocimetry was used to characterize flow fields behind structures. Structures generated flow conditions that benefited fish energetically. Fish had a smoother gait and expended less energy when swimming near a structure, regardless of its orientation. Benefits varied with flow conditions; reductions in energy expenditure were especially apparent at high flow velocities. Results suggest that restoration structures may be most energetically beneficial in stream systems with consistently high velocities and inform restoration by indicating flow conditions in which structures provide the greatest energetic benefits for fish.

A review of radio and acoustic telemetry studies of freshwater fish in New Zealand

Radio and acoustic telemetry have been used in 24 studies of freshwater fish in New Zealand. Although most native species are too small to carry these tags, studies using telemetry have been carried out on four of the larger species, i.e. lampreys (Geotria australis), shortfin and longfin eels (Anguilla australis and A. dieffenbachii) and giant kokopu (Galaxias argenteus). Among the introduced species, telemetry has been used to study movements of brown and rainbow trout (Salmo trutta and Oncorhynchus mykiss) in both rivers and lakes, chinook salmon (Oncorhynchus tshawytscha), koi carp (Cyprinus carpio) and bullhead catfish (Ameiurus nebulosus). To date, studies have almost exclusively been of short-term movements and seasonal migrations. Study objectives range from measuring microhabitats and home ranges to determining the extent of seasonal spawning migrations. The advent of progressively smaller tags will provide increased opportunities to use this technology on a wider range of fish species. Management implications of several studies are presented. Although biotelemetry studies have not yet been used in New Zealand, there are considerable opportunities for using such technology to increase understanding of fish energetics and also stress associated with catch-and-release practices in recreational fishing.