Abstract:Species composition, ecological role, diversity, and clustering characteristics of fish species were analyzed by means of the species similarity, diversity index, and redundancy analysis (RDA) fishery resource surveys data collected in November 2015 (autumn) and May 2016 (spring) in the Zhoushan coastal fishing ground. The results showed that a total of 81 fish species were identified, which belonged to 63 genera in 39 families of 12 orders, with the bulk belonging to offshore, warm-water species. The Jaccard similarity index is 37.04% at the middle dissimilarity level. Analysis showed that the dominant species in the spring was Amblychaeturichthys hexanema, which accounted for 42.16% of the total catches. The dominant species in the autumn was Harpodon nehereus, which accounted for 43.56% of the total catches. The diversity index value of spring was higher than in autumn. However, the two seasonal diversity indices had similar planar distribution. Diversity was observed to be the lowest in the southern region of the survey area increasing toward the north, and a similar trend was seen from east to west in the survey region. The analysis of similarities (ANOSIM) test showed that the differences between the communities were highly significant. The similarity percentage (SIMPER) showed that seven species of fish, including Decapterus maruadsi, Collichthys lucidus, and H. nehereus, were typical species belonging to different groups in the spring. Fish community structure differed in autumn compared to spring primarily in that there were nine species of fish, including Sardinella nymphaea, Engraulis japonicus, and Benthosema pterotum. The results of the RDA indicated that the main environmental factors influencing the structure of fish community in the Zhoushan coastal fishing grounds were salinity and temperature.
