| From December 2020 to December 2021,the biological data of Trichiurus japonicus samples randomly sampled from trawling and windsurfing nets in the East China Sea were obtained through anatomical and biological determination,and the biological characteristics as well as the morphological characteristics and growth of statolith were studied.The following results were obtained:(1)The anal length of East China Sea T.japonicus ranged from 147-380 mm,the average anal length was(256.41±37.38)mm.The average body weight was(367.4±123.84)g,and the average body weight was(50.90-694.9)g.There were significant differences in anal length and body weight between male and female of East China Sea T.japonicus(P<0.05).The relationship between anal length and body weight of total:W=0.00002L2.9604(R2=0.90,n=390,P<0.01),Compared with the relationship between body length and body weight of East China Sea T.japonicus(W=2.464×10-5L2.9019)during 2016-2020,it can be concluded that the habitat environment and nutritional status of T.japonicus in the East China Sea in 2021 may be better than that in 2016-2020.(2)The sex ratio of East China Sea T.japonicus was 2.25:1.Chi-square test showed that the sex ratio was not 1:1(P<0.05).The feeding grade of East China Sea T.japonicus was mainly 0,1 and 2,the empty stomach rate was 36.57%,the feeding grade was relatively low;The maximum stomach somatic index of the East China Sea T.japonicus was 134.44 ‰,the minimum was 4.75 ‰,and the average was 28.96 ‰.The condition factor of East China Sea T.japonicus ranged from 0.98 to 2.26,with an average value of 1.49,and there was no significant difference in condition factor among different sex and anal length groups(P>0.05).The liver weight of East China Sea T.japonicus ranged from 0.10 to 15.10 g,with an average of(2.60±2.26)g;The liver somatic index ranged from 0.02 to 3.94,with an average value of(0.89±0.54),and there were no significant differences in liver weight and liver somatic index between different sex anal length groups(P>0.05).The gonad weight of the East China Sea T.japonicus ranged from 0.07 to 59.30 g with an average value of(7.24±8.52)g,and the gonad somatic index ranged from 0.05 to 16.88 with an average value of 2.48±2.52,and there were significant differences in gonad weight and gonad somatic index among different sex anal length groups(P<0.05).The gonad somatic index of both male and female individuals increased rapidly with the increase of anal length at first,and then decreased significantly after reaching a certain anal length.When the anal length was more than 220 mm,the mean of the gonad somatic index of female individuals were much higher than that of males.(3)The individual absolute fertility of 83 female T.japonicus at or above the maturity stage Ⅲ ranged from 3000.971 to 78264.585 grains,with an average of(27749.95 ±16255.62)grains;The relative fecundity of anal length was 12.35～240.0(grains/mm),with an average of(91.91±45.56)grains/mm;The relative fecundity of body weight was 13.87152.88(grains/g),with an average of(72.69±27.63)grains/g;The distribution of absolute fecundity and relative fecundity of body weight was concentrated,but the distribution of relative fecundity of anal length was dispersed.Egg diameter ranged from 452 to 2063 um,with an average value of(922.94±318.68)um;There was only one peak in egg diameter of stage Ⅲ to V,so it was speculated that the spawning of T.japonicus in the East China Sea was single batch.With the growth of gonadal maturity,the size of egg diameter would increase.(4)The overall shape of the East China Sea T.japonicus statolith is like a long spindle,growing wider,thick in the middle,milky white,thin edge,nearly transparent,uneven surface,can clearly distinguish the dorsal、ventral、rostrum、antirostrum、excisura major and posterio,the dorsal and ventral sides have corrugated protrusions or serrate leaf crystal protrusions,ventral side is smoother than the dorsal side;rostrum is obviously longer than antirostrum;The main excisura major groove extends from the front end to posterio,and the anterior groove is obvious and shallower as it goes farther back;A lobe protrudes from posterio.(5)Five main morphological parameters were obtained by principal component analysis,distance from the rostrum to the antirostrum(DRA),distance from the rostrum to the intersection(DRI),distance from the rostrum to the posterior(DRP),distance from the antirostrum to the posterior(DAP)and distance from the intersection to the posterior(DIP).According to Pearson correlation analysis,the growth pattern of all parts of the statolith of the East China Sea T.japonicus showed allometric growth.According to the independent sample t test,there were significant differences between the sexes in the main morphological parameters of the statolith of the East China Sea T.japonicus(P<0.05),that is,the size of the main morphological parameters of the statolith of the East China Sea T.japonicus was closely related to its sex.The linear function,logarithmic function,power function and exponential function were used to fit the relationship between the main morphological parameters of the statolith and the anal length and body weight of female and male individuals.The results showed that the main morphological parameters of the statolith were significantly positively correlated with the anal length and body weight of female and male individuals.Moreover,the fitting relationship between the main morphological parameters of the statolith and anal length is better than that between the fitting relationship and the body weight,and the variation of anal length can better reflect the change of the main morphological parameters of the statolith in the female and male.Analysis of variance(ANOVA)and minimum significant difference(LSD)were used to study the variation of main morphological parameters of statolith among different anal length groups.It was concluded that the growth of statolith was closely related to the body size of fish. |
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