Biological effects of temperature and salinity on larval quality of Tridentiger trigonocephalus

The Three Gorges Dam project was recently finished and has reportedly caused environmental changes in the Yangtze River estuary. To better understand the tolerance of estuarine fish to varying environmental factors in this region, in this study we examined the effects of temperature (17, 19, 21, 23 and 25°C) and salinity (0, 2, 4, 6, 8 and 10) on the early larval development of Tridentiger trigonocephalus, a representative goby species in the Yangtze estuary. We found that larvae body length and height was decreased at hatch after incubation in increased temperatures. The development of yolk-sac larvae finished at 5 days post hatch. Larvae were lightly pigmented throughout development and their fins developed quickly. The yolk sac volumes of larvae after incubation at 17 and 19°C were markedly larger than volumes at 21, 23 and 25°C. The deformity rates of larvae reared at low salinities were lower than at high salinities, while yolk volumes at low salinities were larger than at high salinities. All unfed larvae died between 13-14 days after hatch. The survival activity index values of larvae reared at low temperatures and salinities were higher than the values at high temperatures and salinities. We conclude that the optimal temperatures and salinities for T. trigonocephalus larval development are 17-21°C and 2-4, respectively. Our findings indicate that the larval quality and fishery resource of T. trigonocephalus in the Yangtze River estuary may be affected by changes in temperature and salinity, which have been reported since the impoundment of the Three Gorges Dam.