Social organization and reproductive behavior of ostraciid fishes from Japan and the Western Atlantic Ocean

Social organization and reproductive behavior were studied in 4 species of ostraciid fishes.Lactoria fornasini andLactoria diaphana from Japan andAcanthostracion polygonius from the western Atlsnyiv were usually found in single male, haremic social groups, although the latter 2 species usually included only 2 females per harem, and individuals in all 3 species foraged solitarily. Elements of both “resource defense” and “female defense” (Emlen & Oring 1977) were evident in the 2Lactoria species, and female defense appeared particularly intense inL. diaphana. Resource defense was apparent inA. polygonius. Lactophrys triquetor occurred in lek-like breeding assemblages at Curacao (Netherlands Antilles) and on the Atlantic coast of Panama. These variations in social organization are discussed and a relationship with feeding habits is suggested. All 4 species appear to be gonochores (demonstrated inLactoria by Moyer 1979). The 2Lactoria spp. showed operational sex ratios (OSR: Emlen & Oring 1977) approaching 1∶1 and a high degree of female spawning synchrony. The occurrence of polygyny in species with 1∶1 OSRs and female spawning synchrony is discussed with reference to the Knowlton (1979) model which predicts monogamy to occur in such situations.