Spatial organisation and behavioural interaction of giant kokopu (Galaxias argenteus) in two stream pools differing in fish density

Abstract

The spatial organisation and behavioural interactions between giant kokopu (Galaxias argenteus) of varying sizes were investigated in two stream pools which varied in fish density. The spatial distributions offish in Pool A were more exclusive, exhibited less overlap, and appeared to be more stable than those for fish in Pool B. The distinct difference observed between the two pools may have been influenced by fish density which was lower in Pool A (0.27 fish/m2) than in Pool B (0.51 fish/m2). A linear, size (weight) related dominance hierarchy appeared to exist within both pools whereby the heaviest individual was the most dominant. Though primarily nocturnal in habit, the social structure and behaviour of giant kokopu (when active during the day) was comparable to that exhibited by other drift-feeding fish in the Northern Hemisphere. © 2003, Copyright Taylor & Francis Group, LLC.