Standard Methods for Sampling North American Freshwater Fishes, second edition

Chapter 7: Coldwater Fish in Large Standing Waters

David A. Beauchamp, Adam G. Hansen, and Donna L. Parrish

doi: https://doi.org/10.47886/9781934874769.ch7

For pelagic sampling in large coldwater lakes, midwater trawling and pelagic gill nets have been recategorized as supplementary for the method of hydroacoustics. The supplementary netting methods provide biological samples for species identification, species composition, and size structure data to complement the hydroacoustic data on depth- and size-specific fish densities. The name “benthic gill netting” was changed to “horizontal giill netting” to standardize with other chapters. The method, however, did not change.

Large coldwater lakes are defined here as standing freshwater bodies with surface area greater than 200 ha that support coldwater fishes such as trouts and salmons throughout the year. These large water bodies can be exposed to extensive wind fetch, which will affect the timing, mobility, and safety of personnel and gear. These considerations become important constraints for deploying, locating, and retrieving sampling gear. Wind and wave energy affect the timing, duration, and stability of thermal stratification, and they can create transient upwelling, thermal fronts, seiches, and other internal waves that affect vertical and horizontal thermal structure and dissolved oxygen availability.