Abstract:

The diversity and trophic levels of fish species in Tong’an Bay were described based on monthly set net fishing surveys from April 2012 to March 2013. A total of 112 species belonging to 88 genera, 53 families and 15 orders were recorded. According to their habitat strata, the fishes were grouped into 3 types, among them 15 species were pelagic, 18 near demersal, and 79 demersal. According to adaptation to temperature, the fishes were divided into 2 types, 84 species were warm water and the other 28 were warm-temperate species. In terms of food habits, there were 4 types, of which 8 species were omnivores, 71 lower carnivorous, 30 middle carnivorous and 3 higher carnivorous. Tachysurus sinensis was the dominant species in summer, autumn and winter, while Polydactylus sextarius, Butis koilomatodon and Tridentiger barbatus were the dominant species in spring and winter. The highest body mass and individual Shannon-Wiener diversity index were 3.26 and 3.29 in November, and the lowest values were 1.78 and 1.77 in February, respectively. The fish community showed distinct seasonal changes, with the lowest monthly change rate of fishes of 40.1% in June, and the highest was 68.6% in March. The mean trophic level also showed significant changes, the minimum was 3.02 in March, the maximum was 3.92 in January, and the average mean trophic level was 3.52. Comparing our data set with previous data from 2003-2004, we found that the species number, species composition and the dominant species in Tong’an Bay all changed significantly. Overfishing, habitat loss and environmental pollution were identified as main factors causing the decline in fish diversity in Tong’an Bay.

Key words: bay, biodiversity, marine food web, trophic level