Nest site choice by the three‐spined stickleback, Gasterosteus aculeatus (form leiurus), in spring‐fed waters

The nest site characteristics of the freshwater three‐spined stickleback, Gasterosteus aculeatus (form leiurus ), were quantitatively investigated in springs and the main stream of the Yamayoke and the Tsuya River system, central Japan. Most nests (93·4%) were on a muddy or sandy substratum, at depths of 10–40 cm (84·3%), in water velocities less than 15 cm s −1 (76·2%) and in the temperature range of 14 to 16° C (82·7%), Spring‐fed localities provided more of these conditions than the main stream channel and hence contained more potential nesting areas. Thus, they were utilized by male sticklebacks both temporally (prolonged breeding season) and spatially (more nest sites).