Preliminary Research On The Relationship Between Growth Conditionsof Mytilus Edulis Linnaeus And Ecological Factors In Gouqi Island

As nowadays there is increasing decline in the ecology, resources andenvironment conditions, under the guidance of scientific outlook of development,sustainable use of marine resources with rationally and effectively scientific viewattracts more and more attentions. Aftera large area of breeding diseases of traditionalscallop took place, Mytilus edulis Linnaeus farming, as an important part in China’smarine aquaculture industry, with its simple farming techniques, strong resistance todisease, develops rapidly. Study of Mytilus edulis has been stuck since the1960sthrough the1980s, due to its failure to keep up with the pace of the expansion ofmussel farming industry in recent years. Many serious ecological problems such aswater pollution and the stocking density exceeding the carrying capacity of watershave been gradually exposed in the breeding process. In this process, there are a fewspecific problems needed to be addressed: like the emergence of differences in growthstates or the incessant disputes on reasonable stocking density of Mytilus edulisLinnaeus. In views of the backgrounds, this paper aims at studying these problems ofMytilus edulis Linnaeus in Gouqi Island of Shengsi Archipelago, the main producingareas of the East China Sea.According to its complete life cycle, during eight cruises to the farming area ofMytilus edulis Linnaeusin Gouqi Island, from September2010to August2011, wecollected over10,000samples to measure associated biology data （shell length, weight,fresh weight of tissue, dry weight of tissue）.Analysis of variance with SPSS （two-tailed test） has been used to identify andquantify growing differences of Mytilus edulis biological parameters of various regions.This paper compares the ecological environmental factors such as temperature, salinity,chlorophyll, turbidity, dissolved oxygen, SPM （suspended particulate matter）, POM （particulate organic matter） that have been monitored in the same period; explores themajor ecological factors which influence the growthing rates of Mytilus edulisLinnaeus in various regions, by applying partial correlation analysis. Viewed from theaspect of water exchange in mussel farming areas of Gouqi Island, we probe into thedistribution characteristics of ecological factors that result in the difference of thegrowth of Mytilus edulis Linnaeus.Meanwhile, using the common standard of mussel farmers’ stocking density inGouqi Island, we establish five gradients of density groups--0.9times,0.8times,0.7times,0.6times of the standard, to conduct field experiments of different densitygradients. The study measures the biological variables and the number of Mytilusedulis Linnaeusin every gradient experiment during both its larvae period and itsharvesting period; monitors the ecological and environmental factors of theseexperiments at a regular interval; maintains and protects the remainedmusselsaccording to normal farming processes.Results showed that:（1） In Gouqi Islandsome of the biological parameters ofMytilus edulis Linnaeus havea relatively significant relation of exponentiation witheach other, such as: body weight and shell length: TFW=L^2.849（n=318, R²=0.940, p<0.0001）.（2） Interregional difference of Mytilus edulis Linnaeus’ shell length （55.64±0.45mm） is small in farming region of Houtou Bay of Gouqi Island, but thedifferences of weight （10.28±0.37g）, tissue of fresh weight （3.61±0.16g）, tissue ofdry weight （0.77±0.06g） among regions are relatively significant, basically showingcharacteristics that the increasing amount of margined weight is heavier than that of themiddle region. Particularly, growing conditions facing steamduring ebb tideis superiorto that during rising tide.（3） Mytilus edulis Linnaeus in larval period grows rapidly ifthe temperature is suitable. After water temperature decreases, growth becomes slow,stagnated, or even has to consume the accumulate denergy of earlier stage （MN Stationwith3.22g/ind in November2010, with2.90g/ind in February2011）. Intuitively, shelllength of the same size will have a big difference in individual mussel weight, freshweight and the dry weight.（4） Since Gouqi Island is anarea of smal scale, temperature（19.00±0.04℃）, salinity （30.36±0.28） and dissolved oxygen （6.63±w0.24mg/l） inthe breeding areas have no significant difference, and have little significant influenceon the growth of Mytilus edulis Linnaeus in each region（P>0.05）.（5） Differences of Chlorophyll （23.23±5.82mg/l）, POM （7.00±0.39mg/l） and PRO （0.25±0.03） in thebreeding areas aremore significant （P<0.05）, and they have significant effect on thegrowth of mussels （P<0.05） the tide when.（6） Water flow velocity in breeding zone(V_1MAX=35.53cm/s) is much smaller than that in the non-breeding areas(V_2MAX=112.85cm/s); the biggest value of flow velocity in the periphery of breedingzone (V_3MAX=35.53cm/s) is greater than that in the intermediate region （V4MAX=20.21cm/s）.（7） Flow velocity increases from the surface to the bottom in breedingzone, while in the non-breeding zone it decreases from the surface to the bottom.（8）Aquaculture facilities hinder the capacity of water exchange, affecting the distributionof the farming region of POM, and resulting indifferent growing speed of Mytilusedulis Linnaeus.（9） Under the situation that both the lengths of breeding ropes and theinterval between ropes are constant, and when stocking density is960individuals perstring, the overall breeding efficiency is higher （39.17yuan/string higher than theconventional by2.36yuan/string）.In accordance with above results, the existenceo of Mytilus edulis Linnaeusaquaculture facilities blocks the capacity of sea water exchange in Gouqi Island,affecting the distribution of particulate organic matter inthe breeding zone, andthusaffecting the growth of the Mytilus edulis. In view of the water exchangecharacteristics of breeding zones in Houtou Bay of Gouqi Island, when suggesting forthe planning and management of breedingzone, it is recommended to set a certainwidth of the vacuum region, where along the direction of tidal fluctuations, musselfarming activities are supposed to be forbidden, which as a whole can promote waterexchange with in the breeding zone, and bring in more peripheral fresh water with richorganisms baits to the inside breeding region of Mytilus edulis Linnaeus, thuscontributing to the growth of the mussels of the middle region and improving theoverall outputof aquaculture production. Meanwhile, it may be appropriate for farmersof Mytilus edulis Linnaeus to adjust the existing stockingdensity to meet the criterionofapproximate960individuals/string on larvae stage.