Morphological differences between breeding stocks of chub mackerel (Scomber japonicus) in the East China and Yellow seas

Abstract

Morphological differences of mature stock of Chub mackerel(Scomber japonicus) were investigated using samples collected during peak spawning in Southern and Eastern Fujian fishing grounds(Wenzhou-Taizhou and Yantai-Weihai fishing grounds) during January to May 2010.Twenty characters were measured within each individual following the truss method.Data were standardized by allometric methods used to remove influences of size differences during the analysis.Furthermore,multivariate analysis of variance was used to examine differ-ences between female and male individuals from four sampling areas.Results indicate that significant differences were observed for characters 2-4 between females and males from Wenzhou-Taizhou fishing grounds(P 0.05).However,no such differences were found for the other characters or for samples from the other fishing ground.Thus,males and females were lumped for further analysis in this study.A discriminant formula was built by prin-cipal component analysis(PCA) and stepwise discriminant function analysis(DFA).Three principal components were constructed,which resulted in a cumulative contributory ratio of 86.63%.Principal component 2 was affected by the length of the second dorsal fin and anal fin,while principal component 3 was especially affected by the extremity of the operculum and starting point of the pelvic fin.Principal component analysis showed that body length was responsible for the morphological difference of mature stock in four sampling areas.The discriminant function of four mature stocks was established by DFA,which showed the range of discriminant accuracy was 97.06%?100% for P1,97.14%?100% for P2,and the general discrimination rate was 99.2%.Finally,this research suggests that the morphological differences of mature stock of Chub mackerel are significant in the four sampling areas in the East China and Yellow Seas.