ISOLATION AND THE DEVELOPMENT OF SHOALING IN 2 POPULATIONS OF THE GUPPY

Socially reared guppies Poecilia reticulata derived from two wild popu lations (Upper and Lower Aripo River, Trinidad) showed a significant r elationship between body size and shoaling tendency. measured as the p roportion of time spent in proximity to a bottle containing conspecifi cs. Larger females shoaled significantly more than smaller females. Fi sh from the high-shoaling population (Lower Aripo) showed significantl y less shoaling behaviour when reared in isolation. Tn contrast, low-s hoaling fish (Upper Aripo) demonstrated no significant change in their shoaling behaviour in response to social isolation. (C) 1996 The Fish eries Society of the British Isles