STUDY ON FISH RESOURCES AND COMMUNITY DIVERSITY DURING SPRING AND SUMMER IN THE COASTAL SPAWNING GROUND OF ZHEJIANG PROVINCE, CHINA

The fish resources and community diversity, and their relationships with the biotic and abiotic environmental factors in spawning ground of Zhejiang province (China) were studied. In this research, data were collected from bottom trawl surveys in spring and summer of 2015 by the least square deviation (LSD) and classification and regression tree. In spring, a total of 92 fish species were sampled in the survey, belonging to 77 genera, 54 families, and 17 orders. In summer, a total of 115 fish species were captured, belonging to 92 genera, 62 families, and 16 orders. In spring, the average value of biomass was 434.40 kg/km² in the whole spawning ground, and the difference of biomass between middle and southern region was statistically significant (P=0.032). The average value of abundance density was 58.42 kg/km² in the whole region, and the difference between northern and southern region was statistically significant (P=0.040). In summer, the average value of biomass was 1532.73 kg/km² in the whole spawning ground, and a significant difference was found between northern and middle region (P=0.010), between northern and southern region was significant (P=0.026). The average value of abundance density was 205.50 kg/km² in the whole region, and the differences between northern and middle region, as well as northern and southern region were both significant (P=0.041, P=0.011). The average values of H′ and D were 1.52 and 2.18 in Spring, correspondingly, the average values of H′ and D were 1.34 and 1.81 in summer, respectively. The classification and regression tree indicated that the main factors affecting the diversity and richness index were depth and turbidity in spring, while the main factors affecting the community diversity level were depth, copepods, temperature, and turbidity in summer. On space, no simple linear relationship was found between latitude and H′, however, H′ value in low latitude waters was significantly higher than that in the high latitude waters when the latitude span was very large. Once, the diversity level was remarkably improved compared with 2008, however, that was closed to the corresponding level in 2011, which indicated that the ecological and environmental factors on the coastal spawning ground of Zhejiang province was relatively stable in recent years.