Seasonality in gonads, fat deposits and condition of tropical surgeonfishes (Teleostei: Acanthuridae)

Lipids are stored in mesenteries surrouding the gut and in paired, retroperitoneal fat bodies dorsal to the anal fin in at least 24 surgeonfishes representing 5 genera (Acanthurus, Ctenochaetus, Naso, Prionurus, Zebrasoma) from Western Mexico, Hawaii, French Polynesia, Great Barrier Reef and the Red Sea. In A. nigrofuscus from the Red Sea and C. striatus from French Polynesia, fat stores and condition index (K=100 W/L³) increased during cool seasons, several months before gonads developed, and declined with the onset of gonadal development. Fat bodies and mesenteric fat deposits developed in all sizes of A. nigrofuscus and C. striatus, and condition paralleled seasonal changes in fat deposits. Gonads of A. nigrofuscus developed in specimens of 76 to 159 mm standard length (SL), while they developed in C. striatus only at lengths>170 mm total length (TL) for females and 195 mm TL for males. Mesenteric fats and fat bodies exhibited similar changes in size, and did not differ in occurrence of major groups of lipids or their relative prevalence. The relative proportions of the major lipid classes differed, however, between these storage sites and other tissues. Muscle, liver and gonads contained less triacylglycerol relative to cholesterol and polar lipid than did mesenteric or fat body lipids. Energy and nutrients acquired during cool saasons with short feeding days appear to support reproductive events during warm seasons, when feeding during longer days fails to meet demands. Fat stores and condition continue to decline beyond the reproductive season until winter.