AB 15:251-260 (2012)  -  DOI: https://doi.org/10.3354/ab00425

ABSTRACT: Flying fishes (Exocoetidae) are commonly found in the epipelagic zone and play an important role in Taiwan in maintaining the stability of the marine ecosystem, local culture and coastal fisheries. However, little is known about their biology and life history, even though several species are of important commercial value in western Pacific countries. Overexploitation of one of the dominant species, the bony flying fish Hirundichthys oxycephalus, is a critical issue in the fishery management and resource assessment of this species. In the present study, H. oxycephalus eggs were harvested off northeastern Taiwan, while adult fish were collected mainly off the southeastern coast of Taiwan. We validated the daily periodicities of the growth increments in 3 otolith pairs based on the successive otolith examination of fish reared in the laboratory from fertilized eggs. The asteriscus was determined to be the most suitable otolith for age determination of the fish. Age (in days) was calculated by counting the number of growth increments on the mounted otolith and adding 11. By using a growth coefficient of 0.0075 d⁻¹, the asymptotic length of these fish was estimated to be 253.86 mm. Back-calculated hatching dates indicated that an occurrence of the summer spawning cohort coincided with the known egg-fishing season off the northeastern coast. On the other hand, the source of the adult fishery off the southeastern coast originated from a new winter spawning cohort. The cohort dynamics of this species were found to be more complicated than previously thought. Our findings could be added to the information already known about the reproductive ecology of H. oxycephalus and used to improve the fisheries management of these fish.

KEY WORDS: Hirundichthys oxycephalus · Otolith · Age and growth · Hatching date · Cohort dynamics