Reproductive Biology Of The Northwest Pacific Saury(Cololabis Saira)

Saury is a kind of pelagic fish which has the characteristics of short life cycle,fast growth,resourceful and widely distributed in the northwest Pacific and coastal waters with high economic value.Although,saury is a not too familiar with people in China,saury also gradually be known along with the national ocean exploration project executed in recent years,and it’s become a kind of important fishing species of domestic of economy.Full understanding of the reproductive biology characteristics of northwest Pacific saury can fill blank for the reproductive biology characteristics of saury.It can provide a reference for later research on the biological characteristics,can supplement and enrich the north Pacific saury reproductive biology information and its changes in biomass resources,can provide a more comprehensive population reproductive biology information to be better in carrying out resources assessment,servicing in the northwestern Pacific saury fishery development in our country,providing the theory basis for reasonable exploitation and utilization of the northwest Pacific saury resources,Also providing reliable basic data for fishery management measures and providing scientific support for reasonable utilization and scientific management of the north Pacific saury fishery resources.According to executing the saury resources exploration of agriculture from 6to 11 months in 2014（38°38′N-44°31′N、146°36′E-162°26′E）and Obtaining saury samples by stick-held net by random sampling and taking back to the lab to do experiments.analyzing the northwestern Pacific saury in biological characteristics by using software such as Excel,Marin,Spss,Origin,Arcgis,WT-1000 GM v2.0 and paraffin section method of histology,analyzed the northwest Pacific saury biological characteristics and the reproductive biology characteristics.The Research including its sex ratio,fork length,body weight,the relationship between fork length,weight and biggest body perimeter,feeding level,grossness,GSI,shape of eggs,different development levels under the length at 50% maturity,the distribution of egg size,fertility and other aspects.The main results can be found as follow:（1）At the end of 2377 samples,male and female ratio was 2.06:1.By chi-square test,sex ratio does not accord with the ratio of 1:1（χ²=137,P<0.05）,the number of female saury has an absolute advantage.（2）The range of samples’ fork length is 189 mm to 346 mm,the average of fork length is 282 mm.The range of female samples’ fork length is 189 mm to 338 mm,the average of fork length is 285 mm.The range of male samples’ fork length is 200 mm to 346 mm,the average of fork length is 289 mm.According to F-test by double sample variance analysis showed that the distribution of fork length has significant differences of male and female individuals(F = 1.39,P = 5.25 x 10^-7 < 0.01).（3）The range of samples’ weight is 27 g to 192 g,the average of weight is 107 g.Statistical analysis of female saury samples found that the range of weight is 27 g to192g,the average of weight is 111 g,the range of male saury samples’ weight is 30 g to184g,the average of weight is 184 g.According to F-test by double sample variance analysis showed that the distribution of weight has significant differences of male and female individuals(F=1.25,P=3.09×10^-4 < 0.01).（4）Making a power function regression with weight and fork length of female and male saury samples,it is concluded that by fitting the curve of weight and fork length,Female W_R=8×10^-8L^3.72,R²=0.93,n=1250,Male W_R=10^-7L^3.67,R²=0.91,n=728.Matching the largest body perimeter and fork length of female and male saury samples can conclude the relationship,Female C=0.45FL-37.32,R²=0.83,Male C=0.45FL-36.16,R²=0.78.（5）The condition factor of female sauries in July is maximal;the condition factor of female sauries in November is minimum.The condition factor of male sauries in November is maximal;The condition factor of male sauries in July is minimum.（6）The range of female saury samples gonad index is 0.017-5.45,the range of male saury samples gonad index is 0.024-2.70,the average of the four month saury GSI have not more than 1,the only part of all samples’ GSI more than 1,it occupies3% of the total number of samples.The trend of GSI is basically same,June-July’s GSI is decline,October-November is rise.（7）The maturity of female saury samples is 60.87% in stage II,21.74% in stageⅢ,13.04 in stage Ⅳ and 4.35 in stage Ⅴ,but they are were not find in the Ⅵstage.All of the mature female saury（Ⅳ+）in the sample is 17.39%.As for the percentage of the male,it is 58.15%,20.79%,13.06%,7.72%,0.28% espectively in stageⅡ,Ⅲ,Ⅳ,Ⅴ,Ⅵ.The mature（Ⅳ+）are 21.07%.（8）The length of the egg diameter was observed and measured under the microscope.Total of 2,506 egg were measured.The higher the maturity,the larger the egg diameter.The cells were mainly concentrated in the early cortical alveoli stage（stageⅡ）,late cortical alveoli stage（stageⅢ）,primary yolk stage（Ⅳ-1 stage）.Peri-nucleolus stage: it was found that the morphology and shape of the egg cells was irregular,the staining color was dark and uniform,the cytoplasm concentration gradually increased,and the thickness of the follicular cells increased gradually as well,the diameter of the follicles was about 51-173 mm.Early cortical alveoli stage（stageⅡ）: Egg cells are irregularly rounded,cytoplasm increased,surface vesicles appeared near the nucleus,the nucleus gradually larger,vesicles gradually increased.The cytoplasm is alkaline,with an egg diameter of about 112-492 mm.Late cortical alveoli stage（stageⅢ）: the cytoplasm of the vesicles continue to increase to multi-layer arrangement,with the trend from the cell center diffuse to surrounding,the oocyte is round or oval,egg diameter is about 180-554 mm.Primary yolk stage:（phase Ⅳ-1）: There are yolk granules in the cytoplasm,yolk granules were dyed dark,the diameter of the egg is about 286-671 mm.Secondary yolk stage（phase Ⅳ-2）:vesicles gradually increased,vesicles filled with yolk and yolk material accumulation,the diameter of the egg is about 405-916 mm.Tertiary yolk stage（phase Ⅳ-3）: the cytoplasm is almost full of yolk material,egg diameter is about 642-1124 mm.Maturation stage（phase Ⅴ）: full integration of egg yolk,filled with the entire egg cells,nuclear membrane disappeared,yolk was dyed dark,egg diameter is about943-1689 mm.Regressive stage（phase Ⅵ）: due to lacking of spawning conditions,mature eggs or immature eggs can not be discharged,finally left a pile of empty follicular membrane.（9）Using the Logistic equation to calculate the relationship of mature rate of northwest Pacific saury and fork length to get the maturity curve.female: P=（?） r=0.033 L50= 323.44 R²=0.80male: P=（?） r=0.046 L50=325.83 R²=0.97（10）the range of northwestern Pacific female sauries’ fertility is 189 17708 pcs,average absolute fecundity is 5481±3298pcs,average relative fecundity is44±26pcs·g^-1.（11）The overall visual error is 97,the average error is 0.29.The period of Ⅲ has the lowest accuracy,The period of Ⅴ has the highest accuracy.