Prey exchange between a stream and its forested watershed elevates predator densities in both habitats

Shigeru Nakano was an extraordinary field biologist, as well as a community ecologist of uncommonly broad vision. Like other great ecologists, his insights were anchored in his deep intuition and knowledge of the natural history of an array of interacting species, in his case, stream fishes, aquatic insects, and birds. Such insight can come only from intensive and prolonged observation in the field. Nakano started his career as a fish biologist, doing detailed work on life histories, diets, and behavior, primarily of Japanese salmonids. In addition to collecting superbly detailed data on fish in their natural environments, he perfected several unique techniques for stream research, including underwater angling which allowed him to remove, measure, mark, and replace individuals in streams at will (2). Nakano's techniques for studying stream fishes expanded as a result of his collaborations with Prof. Kurt Fausch of Colorado State University, who introduced him to the idea of experimental field manipulations. Their collaborations included habitat scale manipulations of insect drift consumed by various salmonid species, with documentation of switches from water column to benthic feeding at different flux thresholds for morphologically generalized vs. specialized salmonid species (3). Nakano's interest in responses of fish and stream food webs to food availability motivated a large scale manipulation of terrestrial insect inputs to the Horonai Stream running through his study site in the Tomakomai Experimental Forest of Hokkaido …