Spatio-temporal variability of fish diversity and dominant species in the Beibu Gulf

Abstract

Based on data collected by quarterly otter trawl surveys in the Beibu Gulf in 2007,the species composition,diversity and dominant species of fishes were analyzed.A total number of 323 fish species belonging to 101 families and 18 orders were collected.The dominant species were Acropoma japonicum,Leiognathus bindus,Trachurus japonicus,Parargyrops edita and Argyrosomus macrocephalus.Data analysis shows an apparent succession of the dominant species with an overall trend of the k-selection species (such as Lutjanus sanguineus and Carcharhinus menisorrah) being replaced by r-selection species (such as Acropoma japonicum,Leiognathus,and Apogonichthys).The abundances of long-lived,large-size,and high trophic level fishes decrease,while those of the short-lived,small-size,and low trophic level increase.The Shannon-Wiener diversity index (H') in the northern common fishing zone (3.60) was the highest,followed by that of the northeast Beibu Gulf (3.58),and the lowest (2.35) appeared in southern common fishing zone..The seasonal variation of the diversity index ranged from 2.96 to 3.77 with an average of 3.31.The diversity index was lower in 2007 than that in 1992-1993,but higher than that in 1998 1999.This indicates that fishing intensity has alleviated in the recent years and has resulted in recovery of the fishery resources.