| Egg size is an important biological parameter reflecting the environment around spawning ground and fish reproductive characteristics. Based on the surveys conducted in <20m depth waters of the central Yellow Sea in six voyages from late April to early July in 2013, the temporal and spatial changes of economic fish egg morphology and size were analyzed. We used Photographed sampling, Image-pro plus image analysis software and SPSS statistical analysis software to generally analyze the spatial and temporal variation of major economic fish egg size in the spring waters. Meanwhile, we analyzed the significant environmental factors referring to temporal and spatial variations, and then we can make further exploration to the impact about the environmental factors on early life history of fish and reproductive strategies of bloodstock.The results indicated that the morphology of Japanese anchovy eggs is elliptical in the study area. Flathead fish eggs, Spanish mackerel eggs are spherical shape. There were no significant differences in egg size among different developmental stages. And both temporal and spatial variations in egg size showed significant difference. Egg size of Japanese anchovy, flathead fish and Spanish mackerel showed a gradual decreasing trend from early May to early July, which was negatively correlated with sea temperature. Eggs of Japanese anchovy, flathead fish and Spanish mackerel began to appear in early May with largest longitudinal section area in the study water. Japanese anchovy eggs’mean longer axis was 1.57 ± 0.09mm, mean shorter axis 0.77 ± 0.04mm, and mean largest longitudinal section area 0.95 ± 0.07mm2, and mean ratio of longer axis to shorter axis 2.03± 0.13. Mean diameter of flathead fish eggs was 1.57 ± 0.09mm. Mean diameter of Spanish mackerel eggs was 1.69 ± 0.09 mm. Minimum egg size appeared in late June:Japanese anchovy eggs’mean longer axis was 1.20 ± 0.07mm, mean shorter axis 0.64 ± 0.03mm, and mean largest longitudinal section area 0.61 ± 0.43mm2, the mean ratio of longer axis to shorter axis was 1.88 ± 0.13. Mean diameter of flathead fish eggs was 1.20 ± 0.05mm, Mean diameter of Spanish mackerel eggs was 1.48 ±0.06 mmThe results in early May, late May and early June showed that the mean diameter of small yellow croaker gradually increased with spawning season progressed. The minimum diameter of eggs appeared in early May, with mean diameter of 1.35 ± 0.05mm. The maximum diameter of eggs appeared in early June, with mean diameter of 1.42 ± 0.08mm. ANOVA teat indicated that there were no significant differences in egg size of small yellow croaker among each voyages. Multiple comparisons showed that egg size in early May did not significantly differ from egg size in late May, but all two differed from egg size in early June. The reasons why this phenomenon happened may be due to the two spawning small yellow croaker population in Haizhou Bay coming from somewhere near the border area separating two subpopulations.Research showed that as the temperature increases, the relationship between the volume of fish eggs (egg size) and sea temperature belongs to one-dimensional linear regression equation. Egg size of Japanese anchovy, flathead fish and Spanish mackerel was negatively related with temperature from early May to early July with the spawning season progressing, which may have relationship with energy reserved that decreased with spawning season. Another reason for egg size decrease with the spawning season pattern is incubation temperature influences the efficiency of conversion of yolk to maternal body tissue. Sampling stations differed from all others significantly in each voyage, which may be not only related to environmental factors relevant to latitudinal clines but also correlated with size-selective predators. The results may to help to provide the basic data for the study of fecundity, spawning season and early life history characteristics of economic fish in Haizhou Bay. |
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