THE SOCIAL AND MATING SYSTEM OF THE HERBIVOROUS REEF FISH SPARISOMA VIRIDE - ONE-MALE VERSUS MULTIMALE GROUPS

We present a detailed description of the social and mating system of t he protogynous reef herbivore Sparisoma viride at the fringing reef of Bonaire (Netherlands Antilles). Initial phase (IP) fish and terminal phase (TP) males occur either in one- or in multi-male groups, which a re compared quantitatively with respect to the use of space, size comp osition, social interactions and sexual activity. One-male groups cons ist of one TP male plus 1-14 IP females, whereas in multi-male groups up to 14 TP males and about twice as many LP fish share a common home range. The two social units further show marked differences in vertica l distribution (one-male groups are restricted to depths between 3 and 22 m, multi-male groups mainly residing < 3 m), size composition (a l arger proportion of small adults live in multi-male groups), size and stability of the range (larger in one-male groups) and sexual activity (daily spawning of one-male group members inside their normal home ra nge; no activity in multi-male groups on the shallow reef). Sexual act ivity occurred daily, throughout the year, with no evidence for tidal tracking or major seasonal or lunar patterns. The one-male groups cons titute less than 20% of the adult stock but control up to 77% of the i nhabited reef. As a result they have access to higher-yield food patch es and to suitable spawning sites inside their home range. Although me mbers of both units appear to defend their common home range against i ntruding conspecifics, the degree of territoriality is clearly higher in one-male groups. We discuss the relative importance of food, shelte r, mates and mating sites as defended resources and some life history implications. The complex social and mating system of S. viride shows much resemblance to that of another Caribbean scarid, Scarus iserti. T his complexity seems to reflect the capacity of individuals to flexibl y adapt their feeding, mating and life history styles to an unpredicta ble environment. We propose that S. viride is a good study animal to t est adaptive explanations for its territorial organization and complex life history patterns.