Identifying the environmental variables that predict crayfish assemblage structure in agricultural headwater streams

Authors: WOOD, TYLER - Indiana University-Purdue University; Smiley, Peter - Rocky; GILLESPIE, ROBERT - Indiana University-Purdue University; Gonzalez, Javier

Submitted to: Freshwater Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2023
Publication Date: 3/1/2024
Citation: Wood, T.C., Smiley, P.C., Gillespie, R.B., Gonzalez, J.M. 2024. Identifying the environmental variables that predict crayfish assemblage structure in agricultural headwater streams. Freshwater Science. 43(1):18-36. https://doi.org/10.1086/729307.
DOI: https://doi.org/10.1086/729307

Interpretive Summary: Crayfishes are keystone species and ecosystem engineers that affect plant and animal abundance in freshwater ecosystems. Unfortunately, many native crayfishes in North America are vulnerable, threatened, or endangered as a result of habitat loss, water quality impairment, and non-native species. Little is known about crayfish-habitat relationships in headwater streams that have been impacted by agriculture. Increasing our understanding of crayfish-habitat relationship and identifying the best environmental predictors of crayfish diversity, abundance, and species composition will provide information that can be used to develop effective conservation strategies. We identified the environmental variables that best predict crayfish diversity, abundance, and species composition in agricultural headwater streams in Indiana, Michigan, and Ohio. Crayfish diversity, abundance, and species composition was best predicted by instream habitat, water chemistry and biotic variables. Our results represent the first comprehensive modeling analysis of crayfish diversity, abundance, and species composition involving watershed, riparian, instream habitat, water chemistry, and biotic variables. Our results suggest that conservation strategies that lead to improve instream habitat, water chemistry, and biotic variables will benefit native crayfishes in agricultural headwater streams in the Midwestern United States. Our results will assist state agencies, federal agencies, non-profit groups, and consulting agencies involved with conservation and management of crayfishes and other macroinvertebrates as well as those involved with managing agricultural watersheds.

Technical Abstract: Little is known about crayfish-habitat relationships in agricultural headwater streams in the Midwestern United States despite the ecological importance of crayfishes. Our research question was which physical, chemical, and biological variables are the best predictors of crayfish community structure in agricultural headwater streams? We sampled crayfishes, fishes, and mussels and obtained watershed, climatic, riparian habitat, instream habitat, and water chemistry data from 17 agricultural headwater stream sites in Indiana, Michigan, and Ohio in 2014 and 2015. Mixed effects model analyses with single variable models found that eight crayfish response variables were influenced (p < 0.05) by 35 predictor variables. Mixed effects model analyses and Akaike Information Criterion tests with single and multiple variable models indicated that each response variable was best predicted by a combination of two to four predictor variables. The best predictive models most frequently contained instream habitat, water chemistry, and biotic variables. Our results suggest that conservation strategies that improve instream habitat, water chemistry, and biotic variables will benefit native crayfishes in agricultural headwater streams in the Midwestern United States.