The Distribution Of Scomberomorus Niphonius Eggs, Larvae And Juveniles And The Growth Of Its Early Life Stage In Xiangshan Bay

Scomberomorus niphonius is a large pelagic species widely distributed in the Bohai, Yellowand East China Sea. Xiangshan Bay is one of the important spawning grounds of S. niphonius. The spawning stocks swim into the Xiangshan Bay and prepare to spawn in early of April every year. This study focus on analyzing the characteristics of the temporal and spatial distribution of fish eggs, larvae and juveniles of S. niphonius in Xiangshan Bay in order to test the relationship with surface temperature, salinity, depth and the abundance of zooplankton. 14 sampling stations were set up, from April 3th to June 3th in 2015, fish eggs, larvae and juveniles of S. niphonius were collected by a small plankton trawls(1 m′2 m, 1.0 mm mesh size), and zooplankton were collected by a plankton net Ⅲ(0.37 m diameter, 0.3 mesh size)every week. Meanwhile the temperature, salinity and depth data at each sampling site were collected. We used the method named hierchy clustering analysis to analyze the similarity of the distribution of eggs, larvae and juveniles of S. niphonius. Generalized additive models has been used to analyze the correlation between the abundance of eggs, larvae and juveniles of S. niphonius and environmental factors. The body length(L,mm) and daily-age(D, days) of larvae and juveniles of S. niphonius were represented by a liner model, a Laird-Gompertz model and an exponential model respectively.The results indicated that, in the first instance, S. niphonius spawned in Xiangshan Bay from the early April to early June with the peak occurring in mid-April to early May. Larvae and juveniles appeared later than eggs, however, short duration. The abundance of larvae and juveniles were high from early May to mid-May. Eggs, yolk-sac larvae and preflexion larvae of S. niphonius mainly concentrated in the outside and middle area. The postflexion larvae and juveniles of S. niphonius mainly concentrated in the outside and middle inshore area and the abundance of St.01, St.03 and St.09 were at a relative high level.Secondly, the eggs, yolk-sac larvae and preflexion larvae of S. niphonius had similar distribution, and the distribution of postflexion larvae and juveniles of S. niphonius was similarly. Under the current role, 48 h later, the eggs and early larvae stage of S. niphonius spread to middle area, and then, spread to outside area, but never spread to the bottom area. The temperature, salinity, depth and the abundance of zooplankton were significantly related to the abundance of eggs. The depth was positively related to the abundance of eggs(P<0.05), and it suggested that spawning stocks of S. niphonius might be tend to spawn in the profundal zone(15-30m) of Xiangshan Bay. The results showed that the surface temperature from 15℃to 19℃ was suitable for the incubation of S. niphonius, and the surface salinity for eggs was from 25.5 to 26.0. The abundance of larvae and juveniles were significantly related to surface temperature, but not significantly related to surface salinity and depth and the abundance of zooplankton. The optimum surface temperature for larvae and juveniles was from 18℃ to 19℃.Last, the liner model, Laird-Gompertz model and exponential model were: Ls = 0.7844 t + 1.1728, R2 = 0.891; Ls=3.385 e3.231(1-e-0.034t), R2=0.904 and Ls=4.2569e0.0647t), R2=0.918, and the Laird-Gompertz model and exponential model can better reflect the growth of larvae and juveniles of S. niphonius, but checked by AIC and BIC, exponential model as the best model. The results of Pearson and Kendall correlation analysis showed that instantaneous growth rate of larvae and juveniles of S. niphonius significantly corrected to temperature, and instantaneous growth rate of yolk-sac larvae, preflexion larvae and flexion larvae of S. niphonius increases first and then decreases as the temperature increase, instantaneous growth rate of postflexion larvae and juveniles of S. niphonius increases as the temperature increase. Based on the characters of spawning and nursery ground and the growth characteristics of larvae and juveniles of S. niphonius, the paper provided information for resource protection and sustainable utilization.