Associations between stream fish and benthos across environmental gradients in southern Ontario, Canada

1. The relationship between fish and benthic invertebrate communities in wadeable streams in southern Ontario, Canada, was examined using three independent and spatially distinct data sets. 2. Associations between fish and benthos were always significant when benthos were identified to family and often at the level of phylum. Identification to genus improved the strength of the fish-benthos association in one case. In contrast, identification to species did not improve the strength of the fish-benthos association. Associations between benthos and fish were weaker for one study utilizing a 'rapid' bio-assessment protocol involving field sorting and identification, and a second study which utilized winter benthic collections. 3. In two surveys, stream temperatures were important to the distributions of both fish and benthos, while in a third survey, fish and benthos were primarily influenced by stream size. In all three studies, fish and benthos were associated with similar suites of environmental variables, suggesting that the fish-benthos associations in these streams was driven by corresponding environmental tolerances. 4. Although there was significant variation in the strength of the fish-benthos association which could be attributed to differences in sampling methodologies, the findings from the present study confirm that stream fish and benthos are significantly associated. Therefore, surveys of benthos can be used to make inferences on the condition of fish community composition.