The Different Of Catch Composition And Effects On The Fishery Resource Of Light Lift Net And Light Purse Seine In Northwest Pacific

The Northwest Pacific has the most abundant fishery resources in the world.Chinese fishing vessels in the area mainly through the light purse Seine and light lift net to fishing Scomber japonicus,Ommastrephes bartrami and Sardinops sagax.In this survey,basic data had been collected based on random sampling by the survey on the catch compositions of light life net and light purse seine,which are two main fishing gears and fishing methods to exploit the pelagic fishery resource,the affection of the two gears on fishery resource had been assessed for optimizing the structure of fishing gear and promoting sustainable utilization of fishery resource in the Northwest Pacific.Based on the survey data collected from light lift net and light purse seine in the Northwest Pacific from August to November in 2016 and from July to August in2017.the characteristics of fishery resource utilization of two fishing methods were compared.Classification and identification of catch species and collection samples and related experimental treatment.The survey includes the location of the work,the types of fishing boats,the parameters of the nets,the composition of the catch and the species,and the biological data of the samples.Conclusion as indicated:1.Light purse seineThe main fishing resources were the pelagic fishery resource and cephalopods.Light purse seine Scomber japonicus fork length range was 14.1~42.2 cm,the dominant length group was 27.0~30.0 cm,accounted for 19.9%.Light purse seine catches a total of 15 species and the species richness index was 0.22,the dominant species of Scomber japonicus,Ommastrephes bartrami and Cololabis saira dominance index were 0.84?0.03 and 0.01,The Catch rate of the juvenile fish of Scomber japonicus(the fork length was less than 22cm)was 12.7%;Light purse seine Ommastrephes bartrami mantle length range was 3.5~43.2cm,the dominant length group was 25.0~32.0 cm,accounted for 19.9%.The Catch rate of the juvenile fish was 23.6%;From August to November,the monthly average Catch Per Unit Effort(CPUE)distribution range of the light purse seine in the same period was(2.6~5.6)�10~3Kg/h,The average catch yield is 12.3�10~3Kg/net.2.Light lift net(in 2016)Light lift net catches a total of 18 species and the species richness index was 0.30,the dominant species of Scomber japonicus,Ommastrephe sbartrami and Sardinops sagax dominance index were 0.53,0.07 and 0.26;The species selectivity of the two fishing methods was better,Scomber japonicus fork length range of Light lift net was10.4~39.8cm,the dominant length group was 17.0~19.0cm and 27.0~29.0cm,accounted for 19.9%and 18.9%.The Catch rate of the juvenile fish(the fork length was less than 22cm)was 24.3%.The proportion of juvenile fish in light lift net was significantly higher than that of light purse seine,but the total number of juvenile fish per net was opposite.Light lift net Ommastrephes bartrami mantle length range was3.0~32.8cm,the dominant length group was 21.0~27.0cm,accounted for 76.8%.The Catch rate of the juvenile fish(the mantle length was less than 25cm)was 63.26%.Light lift net was in a higher proportion of juvenile fish,but the average catches weight of juvenile fish in each haul was similar;From August to November,the monthly average CPUE distribution range of light lift net was(0.8~2.0)�10~3Kg/h,and the average monthly CPUE distribution of the light purse seine in the same period was(2.6~5.6)�10~3Kg/h,The average catch yield is 2.2�10~3Kg/net.3.Light lift net(in 2017)Light lift net catches a total of 13 species and the species richness index was 0.24,the dominant species of Scomber japonicus and Sardinops sagax dominance index were 0.82 and 0.07,The average CPUE was 2.1�10~3Kg/h,and the average catch production was 4.1�10~3Kg/net,the dominant length group of Scomber japonicus was 21.0~23.0cm,accounted for 51%,The Catch rate of the juvenile fish(the fork length was less than 22cm)was 56.6%,During the investigation,the Scomber japonicus and Sardinops sagax stomach content mainly consists of krill,copepods and fish and digest,which is the most important food species of krill feeding,accounting for 77.1%of the sample percentage,the average quality of Japanese mackerel stomach contents were 0.9g.4.differences between light life net and light pure Seine(2016)(1)Catch composition:Scomber japonicus accounted for the quality of light purse Seine were higher than that of light lift net.(2)Yield:The total yield and the average single net yield of the light purse seine were higher than that of the light life net.(3)Catch rate of the juvenile fish:For Catch rate of the juvenile fish of Scomber japonicus and Ommastrephes bartrami,the light purse Seine was lower than the light lift net and the number of the juvenile fish was higher by the light lift net.(4)Catch diversity:The diversity of catch of light purse seine was higher than that of the light life net.(5)CPUE:The CPUE of light purse seine were higher than that of the light life net.5.Differences in the composition of light lift net(2016 and 2017).(1)Catch composition:Scomber japonicus accounted for the quality of in 2016 were higher than that in 2017,the rest of the proportion dropped.(2)Yield:The total yield and the average single net yield of the light lift net in2017 were higher than that in 2016.(3)Catch rate of the juvenile fish:Higher than 2016 in 2017,it was more harmful to supplementary resources.(4)Catch diversity:The diversity of catch of light lift net in 2016 was higherthan that of in 2017.(5)CPUE:The CPUE of the light life net in 2017 was higher than that in 2016The light purse seine has high yield,large fishing intensity and strong damage to fishery resources.The selectivity and catch efficiency of light lift net was lower than that of light purse seine.The fishing intensity can be adjusted according to the change of resources,and the fishing gear and fishing method should be optimized.