Some Biological Characteristics Of Different Geographical Coilia Nasus Populations

Coilia nasus is a kind of mid-small sized fishes with resident andmigration ecotypes. The anadromous population has long been recognizedas very important commercial aquatic products in the lower reaches of theYangtze River. To evaluate the fishery biological characteristics andmorphological distinction in different generation and ecotypes, weanalyzed the Coilia nasus specimens collected in2012and2013. Theresults are as follows:（1）we analyzed458specimens of Coilia nasus collected at Jingjiangin May,2012. The results showed that the spawning stock included4agedgroups with85.81%of age2to3. The body length were14.2to38.9cm ataverage of (25.72±4.08)cm and the body weight varied from9.2to208.4gat average of (69.59±33.73)g. Body length and body weight were fitted intothe function W=0.0028L3.0866(R2=0.9153), The average fatness only was0.38±0.08. Based on the von Bertalanffy growth equation: Lt=40.82[1– e-0.31(t+0.55)], W55)t=262.59[1–e-0.31(t+0.]3, we calculated the asymptotic lengthas40.82cm and the asymptotic weight of262.59g. The age at inflectionpoint of body weight growth curve was2.99when body weight Wt=77.66g.Compared with the study results in1970s, the recruitment and youngsurplus populations of the spawning stock increased significantly inreproductive population. Low-age and miniaturization tendency wasobviously accompanied with fatness decrease. However the growthpotential was still high on the basis of the growth equation. The resultssuggest that active measures such as reducing fishing intensity of thereproductive population and protecting the spawning grounds areimperative to maintain this precious fishery resources.（2）we analyzed the number of vertebrae, ribs and anal fin rays on661specimens collected in three sites. The results showed this three traitswere normal distribution of Coilia nasus populations from jingjiang indifferent years, the average of vertebrae and ribs had significant differencewhile the anal fin rays did not. The number of vertebrae and anal fin rays ofCoilia nasus population from Chongming and Jingjiang were higher thanPoyanghu, however the number of ribs had no difference among this threeecotypes. The numerical of Difference Coefficient were inconsistent basedon these countable properties, anyhow the results still support they werebelonging to the same species. Simple correlation analysis demonstated that traits were significantly correlated with age and the specimens aged at2to3had significant difference in the number of vertebrae, ribs and analfin rays according to the one-way ANOVA analysis result.（3）The Coilia nasus population from Jingjiang and Poyanghu wereregarded as different ecotypes, in this paper we used the multivariatemorphometrics to analysis the truss parameters from them. The resultsindicated that the anadromous population of Coilia nasus from differentyears with significant difference in morphological features related to thehead and motor function. Specimens of different sex did not appear obviousdifferentiation except some morphological parameters related to the chest.Different age groups of migration fishes had no significant distinction andthe resident only had diversity on head. Further analysis of the Coilia nasuspopulation at same age group from different ecotypes showed that the mostsignificant difference between age two followed by three years old andfinally the four age groups.