| Chile Jack mackerel (Trachurus murphyi) are important pelagic species in the southeast Pacific Ocean.The diverse work does not show a clear picture in regard with the stock structure and the results from different authors are not entirely consistent. To determine the stock structure of Trachurus murphyi to inform future fisheries management.Therefore,using morphological method and RAPD analysis we analyzed and evaluated possible population structure differentiation of Jack mackerel in the southeast Pacific Ocean so as to provide theory base for the protection of Trachurus murphyi resource.This study can be summarized as follows:1.Analyzing morphological variablesMorphological data were collected for 60 Trachurus murphyi from the (35°S-40°S,86°W-90°W), for 80 Trachurus murphyi from the(35°S-40°S, 91°W-93°W) and for 11 Trachurus murphyi from the (35°S-40°S,102°W- 103°W),total 151 Trachurus murphyi. Twenty morphological indicators,consisting of 7 measurable indicators and 13 framework indicators,were measured.We derived 19-body-length -based relative indicators. Statistics methods such as analysis of variance,principal component analysis and discriminant analysis were used in the analysis of morphological variables for identifying significant differences in population structure among the three groups described above.Coefficient of variation study suggests that three populations of Trachurus murphyi did not reach the discriminant level of two different subspecies.There were no significant difference between the(35°S-40°S, 86°W-90°W) and (35°S-40°S,91°W-93°W). six morphological proportional variables(Spl1/Tl,Ed/Tl,Hl/Tl,2-4/Tl,3-6/Tl,8-9/Tl)were significant difference between the(35°S-40°S, 86°W-90°W) and 102°W-103°W,and seven morphological proportional variables(Spl1/Tl,Spl2/Tl,1-4/Tl,Hl/Tl,2-4/Tl,3-6/Tl,4-5/Tl)were significant difference between the(35°S-40°S, 91°W-93°W) and(35°S-40°S, 102°W-103°W).In the principal component analysis,eight principal components(PC) were identified.The percentages of variations inherent in the original data that could be explained by these eight PCs were 36.792%,14.293%,6.835%,5.812%,5.138%,4.925%,4.588%,3.447%,respectively. Overall these four PCs explained 81.83% of the total variations inherent in the original variables. For the first PC,the load values of Spl1/Tl,Spl2/Tl,1-3/Tl,Hl/Tl,2-4/Tl were larger than 0.7.A plot of the first and second principal components showed that morphology of three populations were no significant difference.The discriminant functions of the three groups were established,and the discriminant accuracies for(35°S-40°S, 86°W-90°W),(35°S-40°S,91°W-93°W) and (35°S-40°S,102°W-103°W) were 63.3%,72.5%,72.7%.2.Random amplified polymorphic DNA analysis of genetic diversityFour primers were screened from 9 random primers by using RAPD (random amplified polymorphic DNA)technique, 146 randomly selected samples from population(35°S-40°S,90°W-95°W,35°S-40°S,100°W-105°W and 35°S-40°S,105°W-110°W ) were analyzed. 52 loci were detected and 51 of these loci were polymorphic, which accounted for 98.08% of the total loci. The Shannon's index was 0.5202±0.1813, the Nei's genetic diversity index was 0.3500±0.1440, and the GST values was 0.0311. The results indicated that the genetic diversity of the Trachurus murphyi were comparably high, and genetic differentiation was not significant among populations.The intra-population genetic diversity among these 3 groups was: 0.9731,0.9755,0.9784, respectively.The genetic distance between two populations of (35°S-40°S,100°W-105°W)~ (35°S-40°S,105°W-110°W)(0.0218) was smaller than that between (35°S-40°S, 90°W-95°W)~ (35°S-40°S,105°W-110°W)(0.0248) which was in turn smaller than that between the (35°S-40°S,90°W-95°W)~ (35°S-40°S,100°W-105°W)(0.0273)The results indicated that Chilean jack mackerel in the southeast Pacific Ocean(86°W-110°W) would be one population... |
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