The effect of shoal size on patterns of body colour segregation in mollies

Individual white and black mollies Poecilia latipinna spent significantly m ore time near the larger group when given the choice between two shoals of similar colouration to themselves. When given the choice between a large an d a small shoal of dissimilar colouration to themselves, black test fish sp ent significantly more time with the larger shoal while white test fish sho wed no preference for either group. Both white and black mollics chose the smaller of two shoals when given the choice between a large dissimilarly co loured shoal and a small similarly coloured shoal. The results indicate tha t mollies actively discriminate between shoals on the basis of both body co lour and shoal size. However, body colour segregation appears to have a str onger influence on shoal choice. (C) 2001 The Fisheries Society of the Brit ish Isles.