Otolith Morphometrics and Variations Between Two Populations of Sillago sinica (Perciformes, Sillaginidae) in the East China Sea and the Yellow Sea

Chinese sillago (Sillago sinica) is a newly recorded fish species from coastal waters of China. The calcified otolith locating within the inner ear of teleost is an important source of ecological information, and mastering the morphologic features of the otolith is fundamental to fisheries biology. However, the otolith morphology of S. sinica has not been thoroughly studied yet, thus the lack of adequate biological data seriously hampers sustainable utilization and scientific management of this species. This study aimed to explore the otolithic dimensions of S. sinica so as to detect the correlation between otolith morphology and fish body size, as well as compare the otolith shapes between two populations in the East China Sea (ECS) and the Yellow Sea (YS) so as to quantify the phenotypic variations to discriminate the southern and northern S.sinica populations. The variations of left and right otoliths were detected and significant differences were found in otolith shape except for the otolith weight (OW), area (A) and the minimum radius (R_min). The regression relationship between body length (BL) and otolith weight (OW) was described with a linear function, with the expression of \(OW = 0.212 \times BL - 14.225,{R^2} = 0.876\) $OW=0.212\times BL-14.225,R^2=0.876$ , while the optimal power function of body weight (BW) and otolith weight (OW) was \(OW=4.061\times B{W^{0.443}},{R^2}=0.787\) $OW=4.061\times B{W}^{0.443},R^2=0.787$ . In principal component analysis (PCA) based on shape indices, it showed that the cumulative contribution ratios of the first three principal components of bilateral otoliths reached 88.746% and 89.448%, respectively. Fourier analysis indicated that the first seven Fourier harmonics could separately explain 91.471% and 93.563% of the morphological characteristics. The discriminant accuracy rates reached up to over 95% both in the ECS and the YS populations. The obvious differentiation between these two sea areas was detected in the scattergram of the first two principal components, which might be related to local environmental conditions and living habits. The otolith shape variability could be used as a useful tool for population identification of S. sinica. The results contributed to the database on the otolith morphometric data of S. sinica in China and provided references for fishery management of Sillaginidae fishes.