Evaluating Standard Sampling Protocols for Assessing Sport Fish Populations

Led By

Lake and Reservoir Researchers

Study Area

Select reservoirs

Project Status

Ongoing

Research Objectives

• Examine the suitability of specialized gill netting protocols for assessing sport fish populations in key Colorado reservoirs.

Project Description

​Gill nets are commonly used to monitor fish populations. They are lightweight, easy to use, catch multiple sizes and species of fish simultaneously, and provide information (i.e., numbers and sizes) that can be compared through time. Observed trends in catch information from annual gill net surveys are used to inform fisheries management decisions.

The Lake and Reservoir Research group has been investigating the appropriateness of specialized gill netting protocols developed by the Ontario Ministry of Natural Resources that enable biologists to estimate the total number of fish in a lake or reservoir (i.e., “abundance”). Specifically, lake trout and walleye, which are two highly sought sport fish in Colorado.

Researchers have examined two protocols: Summer Profundal Index Netting (SPIN) for lake trout, and Fall Walleye Index Netting (FWIN) for walleye. Both protocols use gill nets set for a defined duration at multiple depths across all regions of a reservoir, resulting in a rapid, comprehensive survey typically completed over 2-4 days.

Other methods for estimating the abundance of a fish population (like tagging and then recapturing tagged fish) in a lake or reservoir are resource intensive, and can be cost prohibitive. Thus, techniques such as SPIN and FWIN can be valuable when in-depth population assessments are needed to help inform complex management decisions. For example, changes to harvest regulations, how to balance top predators with their prey fish populations, or other challenges managers face.

Associated Publications

Beauchamp, D.A., A.G. Hansen, and D.L. Parrish. 2024. Chapter 7: Coldwater fish in large standing waters. In Standard methods for sampling North American freshwater fishes (2^nd edition). Edited by S.A. Bonar, W.A. Hubert, and D.W. Willis. American Fisheries Society, Bethesda, Maryland.

Hansen, A.G. 2019. Size-dependent retention of pelagic-oriented kokanee in multimesh gill nets. North American Journal of Fisheries Management 39:921-932.

Hansen, A.G., M.W. Miller, E.T. Cristan, C.J. Farrell, P. Winkle, M.M. Brandt, K.D. Battige, and J.M. Lepak. 2023. Gill net catchability of walleye (Sander vitreus): are provincial standards suitable for estimating adult density outside the region? Fisheries Research 266:106800.

Pate, W.M., B.M. Johnson, J.M. Lepak, and D. Brauch. 2014. Managing for coexistence of kokanee and trophy lake trout in a montane reservoir. North American Journal of Fisheries Management 34:908-922.