Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Variable Mesh Gill Nets (in Lakes)

Bruce Crawford

doi: https://doi.org/10.47886/9781888569926.ch21

Along areas of the Pacific Northwest coast, gill nets were traditionally constructed of a coarse fiber twine made from willow bark (Coffing 1991) and other materials, such as seal skin (as reported in 1844 by Zagoskin [Michael 1967]) and moose or caribou sinew (Oswalt 1980; Stokes 1985). Linen twine was used for making gill nets beginning in the 1920s (Coffing 1991). Gill nets were used both for set net and drift net fishing. In the 1960s, nets made from synthetic fibers such as nylon came into wider use. Most nets were 50 m or less in length until the 1980s. Nets are generally 50–70 m long, with mesh size varying depending on the salmon species targeted (Charnley 1984).

Variable mesh gill nets have been used for fish population evaluation for about a century. The efficiency with which gill nets capture fish and the versatile use of these nets in lakes and streams have made them a common tool for fishery evaluation (Hamley 1975).

This supplemental technique addresses the use of gill nets targeting salmonids in the Pacific Northwest but can be used for other species as well. The chapter draws extensively from the following papers: Bernabo (1986); Baklwill and Combs (1994); Bonar et al. (2000); and Klemm et al. (1993). Additional insights into use of gill nets can be found in Hubert (1996).

Variable mesh gill nets are appropriate for sampling when fish mortality is not a limiting factor. Gill nets normally kill a high percentage of fish due to the trapping mechanism of the net around the gills. Careful net tending can reduce but not eliminate the mortality percentage. The use of variable size mesh panels in the gill net allows capture of fish of different sizes. As such, this method can be used to collect data on population abundance, stock characteristics, population distribution, and species richness. Gill nets are not species-selective, and as a result, it can be expected that as many or more nontarget species will be captured as target species. In addition, small aquatic mammals and birds will also occasionally become entangled in the mesh and drown.