Abstract:

Based on trawls conducted in Laizhou Bay, China (119°05′-120°00′ E, 37°12′-37°40′ N), in 2010 and 2011, an analysis was made of changes in species composition, dominant species and community diversity of nekton. A total of 85 species were identified, which included 55 fish, 25 crustaceans and 5 cephalopod species. The most species-rich orders were Perciformes (28 species) and Decapoda (24 species). There was obvious seasonal variation in nekton number, mostly influenced by the number of fishes. Sardinella zunasi, Konosirus punctatus and Thryssa kammalensis were the main pelagic fishes in Laizhou Bay, Chaeturichthys stigmatias, Acanthogobius ommaturus and Cynoglossus joyneri were the main bottom fishes, Orgtosaquilla oratoria, Charybdis japonica and Crangon hakodatei were the main crustaceans, while squid (Loliolus sp.) represented the main cephalopods. Loliolus sp., Chaeturichthys stigmatias and Konosirus punctatus were the dominant species in both 2010 and 2011 and the Shannon-Wiener diversity index was highest in summer and lowest in winter. The Shannon-Wiener index was also higher in the north-east area and lower in the south-west. Since the late 1950s, nekton number, especially of fish, has significantly declined due to human activities and climate change impacts. This is particularly true for cartilaginous fish, estuarine species, river-migratory species, large-scale economic fish, flatfish and takifugu. In parallel, dominant species, such as Trichiurus lepturus, Setipinna taty, Engraulis japonicus, Thryssa kammalensis have been replaced by smaller nekton.

Key words: the Laizhou bay, nekton, species composition, dominant species, diversity