Autumnal habitat use of non-native pumpkinseed Lepomis gibbosus and associations with native fish species in small English streams

Habitat use of introduced pumpkinseed Lepomis gibbosus in small European streams has received little study despite the species' potential associations to native fauna of conservation and angling amenity, e.g. brook lamprey Lampetra planeri, European bullhead Cottus gobio, brown trout Salmo trutta. We examined body size, relative body condition, habitat use and species-species associations of pumpkinseed with accompanying fishes in two small streams in southern England during August 2001. Pumpkinseed body condition decreased with pumpkinseed density; the latter correlated with % clay and % riparian grasses in fish < 63 mm FL, with % riparian shrubs in fish 83-92 mm FL and with water depth in fish > 92 mm FL. Most pumpkinseed size classes occurred more often than expected in stretches with conspecifics and with brown trout >300 mm FL; densities of the latter did not correlate with any habitat variables. Indeed, correlations between trout densities and habitat variables were observed mainly in smaller size classes. Habitat associations in other species corresponded to known levels of rheophily; substratum, channel slope, channel width and riparian trees were also important habitat variables. Pumpkinseed dispersal and establishment under conditions of climatic change, which could have ecological and management ramifications, are discussed. [PUBLICATION ABSTRACT] Key words: electivities, canonical correspondence analysis, invasiveness, lag-phase, establishment, condition index, Sussex Ouse