Local habitat features explain the distribution of the imperiled grass pickerel (Esox americanus vermiculatus)

Abstract

We investigated patterns of grass pickerel (Esox americanus vermiculatus Lesueur, 1846) distribution in three watersheds in Ontario, Canada, using site- and reach-scale habitat variables and fish community assemblage data to determine why this species occurs sporadically throughout watersheds despite abundant seemingly suitable, but unoccupied, habitat. Habitat and fish community data were collected using conventional field sampling methods, and reach-scale habitat data were compiled with the aid of a geographic information system. We found that occupied sites had lower baseflow indices and reach slopes but higher conductivity and agricultural land uses than unoccupied sites. More grass pickerel were detected when conductivity, channel cover, and wetlands in the floodplain were highest and bank slopes lowest; this is consistent with habitat preferences described elsewhere in its range. Habitat features at the site scale appeared more important than reach-scale features suggesting that grass pickerel may be using small habitat patches. This study identifies habitat elements important to grass pickerel and offers insights into management implications.