1、I東海區(qū)東海區(qū)底拖網(wǎng)底拖網(wǎng)不同網(wǎng)囊對(duì)小黃魚的選擇性研究不同網(wǎng)囊對(duì)小黃魚的選擇性研究摘要小黃魚(Larimichthyspolyactis)漁業(yè)是我國(guó)四大漁業(yè)之一，是底拖網(wǎng)捕撈重要的捕撈對(duì)象是渤海、黃海和東海區(qū)重要的海洋經(jīng)濟(jì)魚類。近年來東海區(qū)由于環(huán)境惡化和過度捕撈，小黃魚資源量發(fā)生了嚴(yán)重的衰退，為保護(hù)和更有效可持續(xù)利用小黃魚資源，利于近海海洋生態(tài)穩(wěn)定，本試驗(yàn)就東海區(qū)底拖網(wǎng)網(wǎng)囊在不同網(wǎng)目尺寸和不同網(wǎng)目形狀下對(duì)小黃魚的選擇性進(jìn)行了探討。試驗(yàn)采

2、用套網(wǎng)法采集數(shù)據(jù)，極大似然法求得Logistic曲線的選擇參數(shù)和不同的選擇體長(zhǎng)，通過曲線模型擬合拖網(wǎng)的選擇型曲線，統(tǒng)計(jì)軟件SPSS19.1對(duì)漁獲數(shù)據(jù)進(jìn)行分析比較。研究?jī)?nèi)容包括：（1）對(duì)雙船底拖網(wǎng)菱形目網(wǎng)囊在網(wǎng)目尺寸為50、55、60、65、70、75和80mm時(shí)對(duì)小黃魚進(jìn)行選擇性研究，對(duì)不同尺寸的菱形網(wǎng)囊網(wǎng)目的選擇性效果進(jìn)行分析比較；（2）對(duì)雙船底拖網(wǎng)不同網(wǎng)目尺寸40、50、60和65mm的方形目網(wǎng)囊網(wǎng)目和菱形目網(wǎng)囊網(wǎng)目對(duì)小黃魚進(jìn)行選擇

3、性效果進(jìn)行試驗(yàn)，對(duì)不同網(wǎng)囊網(wǎng)目形狀、不同網(wǎng)囊網(wǎng)目尺寸的選擇性數(shù)據(jù)進(jìn)行了分析比較；(3)在兩種網(wǎng)囊網(wǎng)目形狀下，網(wǎng)囊網(wǎng)目尺寸與小黃魚L0.5選擇體長(zhǎng)的擬合曲線和選擇關(guān)系。試驗(yàn)結(jié)果表明：當(dāng)網(wǎng)囊為菱形目時(shí)，（1）網(wǎng)囊為50和55mm時(shí)產(chǎn)生較高逃逸率，捕獲了大量當(dāng)年生經(jīng)濟(jì)幼魚，（2）隨著網(wǎng)目由小變大，網(wǎng)囊捕獲小黃魚的平均體長(zhǎng)、體重逐漸變大，（3）拖網(wǎng)時(shí)間加長(zhǎng)，由于網(wǎng)囊中漁獲積累產(chǎn)生的堵塞效應(yīng)，嚴(yán)重影響非目標(biāo)魚類的逃逸率，（4）小黃魚的50%選擇體

4、長(zhǎng)（L0.5）與不同網(wǎng)目尺寸擬合的直線：L0.5=2.625M30.7（R2=0.915）。當(dāng)方形網(wǎng)囊和菱形網(wǎng)囊比較時(shí)：（1）當(dāng)兩種網(wǎng)囊網(wǎng)目尺寸小于50mm，小黃魚的逃逸率極低，網(wǎng)目結(jié)構(gòu)選擇性差異不明顯。大于50mm時(shí)，方形目網(wǎng)囊逃逸率均高于菱形目結(jié)構(gòu)，但逃逸率差異并不顯著（P＞0.05），（2）網(wǎng)目尺寸為50mm、60mm和65mm時(shí)，方形目網(wǎng)囊的50%選擇體長(zhǎng)（L0.5）分別比菱形目網(wǎng)囊的L0.5大46.5%、16.8%和7.3%，

5、方形目網(wǎng)囊對(duì)于小黃魚具有較好的選擇性，（3）小黃魚的50%選擇體長(zhǎng)（L0.5）與IIITheivityofdifferentcodendsfLarimichthyspolyactisinthebottomtrawlintheEastChinaSeaABSTRACTLarimichthyspolyactisisnotonlyoneofthemostimptantfisheryspeciesofourcountrybutalsotakeab

6、igproptiononbottomtrawl.ItisamajeconomicspeicesintheBohaiSeatheYellowSeatheEastChinaSeaRegion.ThestockofLarimichthyspolyactisdeclineswsebecauseofenvironmentalpollutionoverfisheryintherecently.Theexperimentsdifferentmeshc

7、onfigurationscodendmeshsizestoinvestigatethoughlytheivityescaperateindertorecoverprotectmeefficientsustainableexpoitthestocktothebenefitofthestableoftheoceanecosystem.Itcollectstheiginaldatebyusingcovermethod.iveparamete

8、rsofLogisticcurveareestimatedbythemaximumlikelihoodmethodTheSignificantdifferencesoftwomeshconfigurationwasanalyzedbySPSS19.1software.Thispaperresearchcontentsinclude:(1)TheinfluenceofdiamondmeshcodendonLarimichthyspolya

9、ctiswhenthemeshsizesare50mm55mm60mm65mm70mm75mm80mm.（2）Comparetheivityoftraditionaldiamondmeshsquaremeshcodendwhenthecodendmeshsizeare40mm50mm60mm65mminthebottemtrawl.(3）Combinethetwokindsofcodendmeshsizesthe50%retention

10、lengthregresstheLogisticequationoftheLarimichthyspolyactisTheresultsshowthat:Whenitcomesdifferentsmeshsizesofdiamondcodend(1)Whenthemeshsizesare50mm55mmitdetainsalargenumberofthecommercialjuvenilesofthesameyear(2)Withthe

11、meshsizesbecomelargerLarimichthyspolyactisaveragebodylengthweightincreasesgradually(3)Thelongerthetrawltowedthemeobviouslyblockingeffectwhichcontributetoaseriousimpactonescaperateofnontargetfish(4)Baseontherelation50%ret