Preliminary Analysis On Biological Characteristics Of Albacore Tuna And Yellow-finned Tuna And Tuna Longline Fishing Technology In The Southern Indian Ocean

The data in this paper come from the exploration project of oceanic ultra-low temperature tuna longline fishing vessel"New Century 86"in the southern Indian Ocean from April to July 2018 in Zhejiang Ocean Shijia Co.,Ltd.This paper mainly deals with the biological characteristics of albacore tuna and yellow-finned tuna,the relationship between fishing rate and water temperature,and the relationship between CPUE?Catch Per Unit Effort?and environmental factors.The fishing technology was studied and investigated.In this paper,the biology of tuna was statistically analyzed by statistical and regression methods.The relationship between CPUE and environment is analyzed according to the spatial resolution of 1°×1°for 78 d production statistics of fishing boat No.86 in the new century by using the drawing function of software ODV?Ocean Date View?.The generalized additive model?GAM?was used to fit the relationship between standardized CPUE and environmental variables to obtain the spatial distribution and habitat preference of tuna.The data measured by temperature and salt depth instrument are analyzed qualitatively and statistically by using EXCEL drawing function,and the 78d0¹00m water is analyzed qualitatively.The relationship between CPUE and water temperature was obtained by graphic analysis of layer water temperature and CPUE of longfin and yellowfin tuna,and the relationship between CPUE and environmental factors was analyzed by SPSS.The results are as follows:?1?the dominant forked length group of albacore tuna was 0.81±0.90m,the relationship between the weight of the original fish and the fork length was W=0.0002L^2.469,R²=0.9324?regardless of sex?;W_M=0.0409L^2.8636,R²=0.8798?male?,and the relationship between the weight of the original fish and the length of the fork was W=0.0002L^2.469,R²=0.9324.W_F=0.046L ^2.8404,R²=0.852?female?.The relationship between the original fish weight and the processed fish weight was D=0.1175L^2.6089,R²=0.8851?regardless of sex?,D_M=1.2545L^2.0757,R²=0.6128?male?;D_F=0.1313L^2.5848,R²=0.9045?female?.The relationship between the original fish weight and the processed fish weight wasW=1.002D+0.9836,R²=0.9991?regardless of sex?;W_M=0.9946D+1.1738,R²=0.9972?male?;W_F=1.0026D+0.9952,R²=0.9985?female?.The dominant fork length of yellowfin tuna was 0.90?1.3 m,and the relationship between the weight of the original fish and the fork length was W=0.1113L^2.6421,R²=0.9153?regardless of sex?,W_M=0.1254L^2.6168,R²=0.8794?male?W_F=0.0897L^2.6876,R²=0.9432?female?.The relationship between the weight of the original fish and the fish weight after processing was D=0.036L^2.8247,R²=0.9142?regardless of sex?;D _M=0.0314L^2.8546,R²=0.9366?male?,D_F=0.0298L^2.8628,R²=0.8818?female?.The relationship between the original fish weight and the processed fish weight was W=1.2476D+0.7017,R²=0.9772?regardless of sex?;W_M=1.1838D+2.948,R²=0.9769?male?;W_F=1.1951D+2.6307,R²=0.9703?female?.The main stage of gonadal maturation was stage II,and the feeding grade was grade 1 and grade 2.?2?The highest water layer of CPUE of albacore tuna is 67×74 m water layer,the CPUE is 41.56 tail/thousand hook,the next is 61×66 m water layer,the CPUE is 0.95 tail/thousand hook,and the CPUE is the highest at 17.0¹7.9?at the water temperature of17.0¹7.9?.The results of factor analysis showed that date and temperature were the most important factors affecting the catch rate of albacore tuna,and the eigenvalues were2.997 and 1.173 respectively,which were all greater than 1,and the cumulative contribution rate of the two factors reached 69.499%.?3?The length of the longline is 25 m and the distance between the two branches is 36mm.in order to prevent tuna swimming in the course of operation from damaging the fishing line,it is suggested that the distance between the two branches should be lengthened relatively.Tuna is a phototaxis fish,in order to improve the fishing rate,it is suggested to add fluorescent bait.