Study On Otolith Morphology And Growth Of Three Kinds Of Larval And Juvenile Fish And Their Relationship With Environment In The Lower Reaches Of The Liujiang River

Fish otoliths are biological crystals in the inner ear of fish,mainly composed of calcium carbonate,used to regulate balance and hearing.It has the characteristics of the particularity of structure,daily accumulation of growth,the responsiveness of environment,stability of the composition and so on.It has a wide range of applications in fishery management and fish research.In addition,otolith can also be used for fish age and age identification,egg-laying site prediction,early life history and other aspects of the study.With Neosalanx taihuensis,Oreochromis niloticus,Tilapia zillii,this study,which base on the otolith morphology method,analysis method,Fourier ellipse method and otolith identification of age method,comprehensively do the research of otolith morphology,otolith age and the application on the identification of population,the identification of otolith age,fish growth.Moreover,this study also combines the collected environment variables for Corresponding analysis.The purpose is to provide biological information of three kinds of fish,provide basic data and basis for fishery management and sustainable development of Liujiang River,and provide basic information for fish otoliths research.The main achievements are as follows:(1)Otoliths of Neosalanx taihuensis have no obvious characteristics.There was no obvious differentiation between rostrum and antirostrum on otoliths of Neosalanx taihuensis.Its contour was relatively smooth,and the difference between left and right otoliths was not significant.The otoliths of Oreochromis niloticus are very similar to Tilapia zillii.The rostrum and antirostrum are smooth and large radians,with uneven Outlines but no serrations.There was no significant difference between the left and right otoliths of Oreochromis niloticus and Tilapia zillii,but the coefficient of variation of otoliths morphology of the two fishes was large.(2)In the fitting of traditional parameters and body length of the otolith,the power function model was the best fitting model for the three larvae.The AIC and BIC values of this model were the lowest and the fitting degree was good,which could well explain the data situation.By fitting the model,the relationship between body length and otolith area,circumference,length and width can be well expressed and predicted.In the calculation of all AIC and BIC models,the minimum value is the same model,and there is no problem that the penalty term in the BIC formula is too large in the face of some large sample sizes,and AIC and BIC selection model is not unified.(3)In the principal component analysis of Neosalanx taihuensis,a total of 12 principal components with eigenvalues greater than 1 were obtained.The explanation rate of the first principal component to the total variance was 34.2444%,and the explanation rate of the first12 principal components to the total variance was 90.9815%.In the principal component analysis of Oreochromis niloticus,a total of 11 principal components with eigenvalues greater than 1 were obtained.The total variance explanation rate of the first principal component was25.2313%,and that of the first 11 principal components was 89.9671%.In the principal component analysis of Tilapia zillii,a total of 10 principal components with eigenvalues greater than 1 were obtained.The explanatory rate of the first principal component to the total variance was 25.0232%,and that of the first 10 principal components to the total variance was 88.5863%.Through principal component analysis,the discriminant complexity caused by excessive parameters in the subsequent discriminant analysis is effectively avoided,and more Fourier harmonic value information describing the contour is retained.(4)The discriminant analysis results show that the best discriminant analysis based on traditional otolith parameters effect,especially in the difference between Neosalanx taihuensis and other two kinds of tilapia.The discriminant accuracy is 87.6%in the distinction of Neosalanx taihuensis and Oreochromis niloticus.The distinction between Neosalanx taihuensis and Tilapia zillii,discriminant accuracy is 82.8%.In the distinction of three kinds of larvae fish,The accuracy rate was 62%.Secondly,the discriminant analysis based on the traditional parameters of otolith and Fourier harmonic value also achieved good results.In the intra-species discriminant analysis,the discriminant analysis based on the traditional parameters of otoliths had the best effect,but the overall situation was not ideal.The discriminant accuracy rate of Oreochromis niloticus and Tilapia zillii was 59.5%.The results show that the traditional parameters still have a certain application value,and the discriminant effect is better for some otolith.(5)The interval between light bands and dark bands of the daily ring of Neosalanx taihuensis was shorter,and the dark band of the daily ring was thinner.The interval between the light bands and dark bands of the daily ring of Oreochromis niloticus and Tilapia zillii is longer,and the dark band of the daily ring is wider.The optimal growth models of Neosalanx taihuensis carp were Von Bertalanffy growth equation model and Logistic growth equation model,and the goodness of fit(R~2)of Von Bertalanffy growth equation and Logistic growth equation were both 0.896.All of them have a good fitting degree.The optimal growth model of Oreochromis niloticus and Tilapia zillii was Logistic growth equation model,and the goodness of fit(R~2)of Logistic growth equation for Oreochromis niloticus and Tilapia zillii was 0.791and 0.857,respectively.Through the fitting of the growth model,this study can well predict the growth of fish.(6)The hatching peak of Neosalanx taihuensis is From February 1st to March 31st,and the spawning time of Neosalanx taihuensis is mainly from January to March.The spawning peak of Oreochromis niloticus and Tilapia zillii is from May 1 to June 15.Pearson correlation analysis showed that two Oreochromis mossambicus species spawning was significantly correlated with temperature,but not with dissolved oxygen,conductivity,flow rate,transparency,water level and flow rate.(7)Through literature statistical analysis,this research obtained influential countries,institutions,journals and authors in the research field of fish otolith.Through keyword co-occurrence analysis,this study found that in the field of fish otolith research,both in terms of research output and quality,as well as research cooperation,the United States occupied a leading position.Otolith chemistry,otolith structure and fishery research,age and growth are the focus of otolith research.