Social preferences of juvenile lemon sharks, Negaprion brevirostris

Group living in sharks is a widespread phenomenon but relatively little is known about the composition and organization of these groups. In binary choice field experiments juvenile lemon sharks were attracted to conspecifics presumably to form groups. Experiments investigating size assortment preferences indicated that lemon sharks aged 2–3 years (but not 0–1 years) preferred to spend more time with a group of size-matched individuals than unmatched ones. Furthermore, in species association tests lemon sharks spent significantly more time associating with conspecifics than with a sympatric heterospecific, the nurse shark, Ginglymostoma cirratum. These findings enhance our knowledge of group-joining decisions in sharks indicating that active mechanisms can play a role in the formation and composition of shark groups.