Morphological Characteristics And Differences Of Trace Elements Of Collichthys Lucidus Otoliths In The Yellow And East China Sea.

Collichthys lucidus belongs to Perciformes,Sciaenidae,and the genus Collichthys,commonly known as big head treasure,plum fish,etc.It likes to live in the middle and lower waters off the coast,has the characteristics of wide temperature and salt,and has a wide distribution range,from the estuary of the Yellow Sea and Bohai Sea to the East China Sea.Because of its delicious meat and high yield,it has become one of the favorite aquatic products caught by coastal fishermen and an important small economic species in China.Because of the wide distribution of the juvenile fish,and the overexploitation of offshore fishery resources,its resource situation is not optimistic.Studies have shown that the resources of Collichthys lucidus in the Yangtze River Estuary and the Pearl River Estuary have been overfished,so the study of Collichthys lucidus should be paid enough attention.In this paper,the morphological and growth characteristics of otoliths in different populations were studied,and the morphological differences of otoliths in different populations were compared by traditional morphological methods and elliptic Fourier analysis.Finally,the micro-chemical differences of otoliths in different populations were discussed based on the otolith element fingerprint analysis of LA-ICP-MS technology,hoping to improve the basic reference for the conservation and sustainable utilization of otoliths in coastal areas of China.The specific research results are as follows:(1)Study on the morphological characteristics and growth characteristics of otolith in the black-headed fish.The morphological characteristics of otolith were observed by shooting high-definition otolith pictures of the Collichthys lucidus.The otolith of Collichthys lucidus is mainly in the shape of a micro-spindle,with a thin periphery and a thick middle,a narrow head and a short tail,and there is no significant difference between the left and right otoliths.There are a few crystalline protrusions on the inside.The otolith is slightly transparent and serrated in edge,opaque in the middle,and the lateral auditory sulcus runs through the otolith in an arc shape.Then,linear,logarithmic,power function and exponential function were used to fit the relationship between the parameters of sagittal otolith and fish growth.The results showed that the long and short diameters of the sagittal otolith increased with the increase of body length and weight.The ratio of short diameter to long diameter of otolith tends to be stable(0.75),and there is a significant linear correlation.The long diameter and short diameter of otolith are both exponentially related to fish body length and power related to fish body weight.Otolith weight is exponentially related to fish body length and linearly related to fish body weight.There is a significant power function correlation between otolith weight and otolith length and short diameter.The prediction of random forest model shows that the contribution rate of otolith basic morphological parameters to fish body length and weight is different,and the contribution rate of otolith weight to body length(0.69)and body weight(0.79)is obviously higher than other parameters.Using otolith morphological parameters to predict the body length and weight of two kinds of fish,the prediction accuracy is91.69% and 94.01%,and the average absolute error(MAE)is 0.9932 cm and 1.57 g,so the overall prediction result is good.(2)Study on the morphological differences of sagittal otoliths in different geographical populations of Collichthys lucidus.In order to study the morphological differences of sagittal otoliths in different geographical groups,203 fish were collected from Haizhou Bay,Jiangsu Province(69 fish),Lusi Fishing Ground,Jiangsu Province(66 fish)and Xiangshan Mountain,Zhejiang Province(68 fish).Traditional morphological measurement was used to show the otolith morphological differences,and elliptic Fourier analysis was used to show the otolith contour differences.At the same time,combined with principal component analysis and discriminant analysis,the otolith morphological differences in the three sea areas of Jiangsu Haizhou Bay,Lvsi Fishing Ground and Zhejiang Xiangshan Port were compared and analyzed.The results show that S-K test results show that 14 of the 19 traditional morphological indexes conform to the normal distribution,and 20 Fourier harmonics all conform to the normal distribution.Non-parametric test was carried out on the indicators that did not conform to the normal distribution,among which X6,X3 and X7 had population differences.One-way ANOVA analysis is made for the indicators that conform to the normal distribution.Among them,X4,X5,D1/D6,D2/D6,D3/D6,D4/D6,D7/D6,D8/D6,D9/D6,D10/D6 and D11/D6,which are traditional morphological indicators,have significant differences among different sea areas,while h1,h2 and h3 are the Fourier harmonics.The results of principal component analysis of traditional morphological indicators show that there are three principal components with eigenvalues greater than1,with a cumulative contribution rate of 92.59%,and seven principal components with Fourier harmonic eigenvalues greater than 1,with a cumulative contribution rate of83.97%.From the discriminant analysis results,the discriminant success rate of elliptic Fourier analysis is 71.9%,which is better than the traditional morphological measurement method of 66.4%.It can also be seen from the scatter chart that elliptic Fourier analysis method can distinguish different groups more effectively.The average shape construction of otolith shape contour based on elliptic Fourier harmonic shows that Haizhou Bay population is different from Lvsi population and Xiangshan Port population,and the main difference lies in the position of the posterior end of otolith and the main sulcus.The contour between basal leaves,wing leaves and main furrow of Haizhou Bay population is smoother,and the main furrow is not obvious.On the baseline of 0,Xiangshan population and Lvsi population have longer diameters than Ganyu population,while on the baseline of 90,the diameters of the three populations have little difference.On the whole,there is little difference between Lvsi population and Xiangshan population,and the contour coincidence degree is high,which also confirms the results of otolith morphological difference analysis.It is considered that the Haizhou Bay population can be distinguished from the Lvsi population and Xiangshan Port population,and can be divided into one group separately.The otolith morphology of Lusi population is similar to that of Xiangshan Port population,which may belong to the same group.However,Haizhou Bay population is located in the northern part of the Yellow Sea,far away from Lusi population and Xiangshan Port population,and can be identified as a separate ecological group,so there is a great difference in otolith morphology.(3)Study on the differences of trace elements in otoliths of different geographical populations of the black-headed fish.Trace elements in the otolith core area and marginal area of Prunus spinosa from three different sea areas in China were determined by LA-ICP-MS otolith element fingerprint analysis technology,and the differences among three different populations were discussed and analyzed.One-way ANOVA showed that except for Ba/Ca in the core area,there were significant group differences in the micro-chemical elements at the core and edge of otolith in the black carp.Linear discriminant analysis can also distinguish Haizhou Bay population,Xiangshan population and Lvsi population,and the overall discriminant success rate is 82.2%,showing strong group identification ability.From the scatter plot of discriminant analysis,it can be seen that function 1 and function 2 can effectively distinguish the group of Collichthys lucidus,and the contribution rate of function 1 to the success of discriminant analysis reached 87.8%.It is considered that otolith element fingerprint analysis based on LA-ICP-MS technology is really effective and feasible to identify the population of Collichthys lucidus,and the ratios of Sr/Ca,Mg/Ca in the otolith core area and Sr/Ca,Ba/Ca and Mg/Ca in the edge area are significantly different,which can be used as the identification of the population source of Collichthys lucidus for environmental element fingerprint.