| The Yellow River is the second largest river in china with lager amount of freshwater and nutrients to the Bohai Sea. The Yellow River Estuary and its adjacent area is an important fishing area which is a spawning, nursery and feeding ground for many migratory economic species from the Yellow Sea and Bohai Sea. However, with the increasing demand for marine resources and aggravation of disturbance of human activities, community structure has been great changed.Based on the data from bottom trawl and beam trawl suverys in Spring and Summer, 2007, community structure, biology diversity, and main biological characteristics of dominant species were analyzed , effect of different fishing gears on fishery resource was discussed, and a preliminary annlysis of the reasons for changes in fishery resources was carried out, in order to provide reference for development and utilization of fishery resource and biodiversity conservation.It is found by analysis that 59 species were obtained from this investigation, which fishes were 26 species, 20 genera, 14 families and 6 orders; shrimps were 8 species, 7 genera, 5 families and 2 orders; crabs were 11species, 9 genera, 7 families and 1 order; cepgalopods were 5 species, 3 genera, 3 families and 3 orders; and gastropods were 9 species, 8 genera, 6 families and 4 orders.In beam trawl survey, the average catch biomass per net was 0.93 and 2.12 kg/h in spring and summer, moreover R, H′and J′were 3.61, 2.277, 0.64 in spring and 3.97, 2.743, 0.76 in summer, respectively. The results showed demersal biological resources in summer were richer than that in spring as well as diversity index of the community. There were few large-scale economic species with small proportion, and small-sized species were predominate in composition of catches, moreover dominant species were Nassarius variciferus, Chaeturichthys hexanema, Oratosquilla oratoria etc..In spring survey, catch weight and nu mber per area swept hourly were 101.8 kg/(h·km~2), 10995 ind/(h·km~2) and 46.1 kg/(h·km~2), 14289 ind/(h·km~2) in bottom rawl and beam trawl, respectively. In addition catch species per net was higher than beam trawl significantly. The similarity of composition of catches between beam trawl and bottom trawl was low to 0.6349. Index R,H' and J' of beam trawl were 3.61, 2.28, 0.64 and those of bottom trawl were 3.55, 2.40, 0.72, respectively. The results showed that diversity of bottom trawl was higher than that of beam trawl. Furthermore, dominant species was only gastropods - Nassarius variciferus, Nassaricus succinctus, Neverita didyma, which took an absolute advantage in beam trawl. However, dominant species of bottom trawl were different from that of beam trawl, which were Oratosquilla oratoria, Nassaricus succinctus, Nassarius variciferus and Chaeturichthys hxanema. It is suggested that both of CPUE and selectivity of the two fishing gears were low and these gears caused great damage to the larves.Environmental investigation showed that the Yellow River Estuary was water eutrphication, COD was over standard ,so was phosphate, and petroleum was slight pollution in 2007. Combined with historical data, the paper analyzed the changes of water quality environment and fishing intensity and effect on fishery resources in Yellow River Estuary .The analysis showed the changes of community structure resulted from many reasons in Yellow River Estuary, and water flow cut-off, seawater pollution and over fishing.were the main causes of low diversity, miniaturization and low quality of fishery resources. Based on the results outlined, this paper brought forward some suggestions for biodiversity conservation in Yellow River Estuary. |
PDF Full Text Request