Ecological Group And Resources Of The Nekton In The Coastal Water Of Lvsi Fishing Ground

To understand the spatial and temporal distribution pattern of the nektoncommunities and seasonal variation in the nekton communities, temporal changes inspecies composition and community structureof the nekton community in the coastal ofLvsi fishing ground were examined based on data from bottom trawl surveys duringspring(May) and summer(September) of2010.The dominant species, the impacts of theenvironment on the distribution of the communities, spawning and feeding habitat ofdominant species were also discussed. The result indicated that a total of66nektonspecies was identified, among them21was fish,11was shrimp and8was crab. In spring,21was fish,11was shrimp and7was crab. The average weight and number density offish was76.35kg·km-2in springand1.33×103ind·km-2. The average weight and numberdensity of shrimps was24.21kg·km-2and12.68×103ind·km-2. The average weight andnumber density of crabs was121.47kg·km-2and7.50×103ind·km-2.The dominantspeciesin spring was Larimichthys polyactis, Cynoglossus joyneri, Cynoglossussemilaevis, Cociella crocodilus, Miichthys miiuy, Palaemon gravieri, Alpheus juponicusand Alpheus distinguendus. Most of them were warm temperature adapted. In summer,28was fish,15was shrimp and6was crab. The average weight and number density offish was35.12kg·km-2in springand2.02×103ind·km-2. The average weight and numberdensity of shrimps was2.19kg·km-2and1.30×103ind·km-2. The average weight andnumber density of crabs was53.05kg·km-2and1.60×103ind·km-2.The dominant specieswasCollichthys lucidus, Coilia mystus, Parapenaeopsis hardwickii and Solenoceracrassicornis, most of the species were belonging to theIndo-West-Pacific warm waterregion.In spring, it was mainly composed of warm temperate species, accounting for45.16%and72.93%in the individual density and weight density of fishes,shrimpdomint specie Palaemon gravieri wasaccounting for52.76%and64.03%in theindividual density and weight density.In summer, the sea water temperature began toincrease, in the meantime, a large quantities of freshwater found in the area, for the influence of the rainy season and Changjiang diluted water. Consequently,fishcommunities made an obvious succession, and warm water species became thenumerically dominant (75.15%). Estuarine warm water species such as Collichthyslucidus and Coilia mystus were predominant species in summer, most of the specieswere belonging to theIndo-West-Pacific warm water region. The shrimp communitiesmade an obvious succession (R=56%), and warm water species became the numericallydominant, such as Parapenaeopsis hardwickii and Solenocera crassicornis werepredominant species in summer, most of the species were belonging totheIndo-West-Pacific warm water region. The warm-temperate species however, weredistinctively decreased during summer, neritic and nearshore species were alsodecreased during summer. In short, nekton ecological groups change in the coastal ofLvsi fishing during the spring and summer is related with seasonal and hydrologicalchanges.