REPRODUCTIVE-BIOLOGY OF AWAOUS-GUAMENSIS, AN AMPHIDROMOUS HAWAIIAN GOBY

Spawning season, size at first reproduction, oocyte maturation, and fe cundity of Awaous guamensis, an amphidromous Hawaiian goby, were studi ed from June 1989 through May 1991 in the Wainiha River, Kaua'i, Hawai 'i. Female fish larger than 73 mm standard length (SL) had mature gona ds from August through December in 1989 and 1990. Gonadosomatic index (GSI) values for mature females ranged from 0.2 to 14.5 during the spa wning season. Male fish larger than 64 mm SL had elevated GSI values f rom June 1989 through December 1989 and from August 1990 through Decem ber 1990. Mature sperm were found in two male fish collected in Januar y and February. GSI values for mature males ranged from less than 0.01 to 4.0 in the spawning season. Size-frequency distributions of measur ements of vitellogenic oocyte diameters and microscopic observations o f oocytes indicated this species has group-synchronous oocyte developm ent. Ovarian maturation stages examined over a 29-month period suggest that members of the stock spawned at different times within the spawn ing season, although mass spawning events have been documented for thi s species. Estimates of clutch sizes from nests measured in situ were comparable to estimates of potential fecundity from in vitro examinati on of ovaries, and indicated that female fish deposited an entire clut ch during a spawning event. No evidence for multiple spawning by an in dividual fish in a single season was found. However, microscopic obser vations of brown bodies in some ovaries suggested that individual fish probably spawn more than once in a lifetime.