Climate-induced changes in the relative abundance of game fish inferred from digital catch log data

Abstract

Climate change can have both direct and indirect impacts on food webs and fish populations. Growing evidence suggests that these impacts are affecting the relative abundance and presence of freshwater fishes. It may be possible to detect climate-induced changes in game fish populations by analyzing data from Fishbrain, a smartphone application that anglers in the United States have used to report catches from 2015-2020. We used generalized linear mixedeffects modeling to determine the temporal trend in catch proportions by subbasin, and then mapped the location of these trends to identify spatial patterns. Results suggest that warm-water species are becoming more common in catches, usually at the expense of cool-water species. These patterns were strongest in the Great Lakes region, the Northeast, and parts of the West Coast. Single-species analyses detected increases in Largemouth Bass (Micropterus salmoides), declines in Channel Catfish (Ictalurus punctatus), Northern Pike (Esox lucius), and Rainbow Trout (Oncorhynchus mykiss), patchy results for smallmouth bass (Micropterus dolomieu), and no response in bluegill (Lepomis macrochirus). Spatial results of the single-species analyses were interesting and will be discussed. Despite the short time frame of this study (6 years), our analyses of catch data produced results that were consistent with expected changes in the relative abundance of game fishes in response to climate change. Future work should focus on refining the use of app data as a tool for monitoring game fish responses to climate change, especially as the length of the time series increases.