Application Of Otolith Morphology In Stock Separation Of Scomberomorus Niphonius And Age Estimation Of Johnius Belengerii

Otoliths of teleost fishes are small, calcareous structures located within the innerear, whose primary function is the detection of sound and maintenance of the bodyequilibrium. In addition, otoliths are widely used as indicators of fish age and growthat annually, daily and seasonal levels. Recent developments in the tools used fordetermining otolith’s microconstituents have opened up possibilities of studyingmigrations and stock identity as well as using isotopes to reconstruct past life historyof fishes, some good progress has made.The main findings were as follows:(1) Otolith shape is species specific and is anideal marker of fish population affiliation. Geographic variability in sagittal otolithsshape of the Japanese Spanish mackerel (Scomberomorus niphonius) was studied totest the stock discrimination and potential of the stock separation. A total of164sagittal otoliths were collected by the commercial fishing vessels from April-June2010in three spawning grounds of the Yellow Sea and Bohai Sea. Otolith wasdescribed using variables correlated to size (otolith area) and shape (rectangularity,circularity, and20Fourier harmonics).To minimize the potential effect of the fish sizebetween three fishing grounds, for this purpose the fishes having (400-550mm) forklength were selected. The discriminant function analysis conducted with standardizedotolith shape indices and Fourier harmonics produced classification success ratesranging from57.0%to88.2%and worked well in the separation between the BohaiSea group and the Yellow Sea group. No significant differences were detectedbetween the three groups in Lvsi spawning ground. The otolith variables showed adistinct gradual variation tendency with the movement of fish schools from south tonorth. Our results supported managing the Bohai Sea group and the Yellow Sea groupas single fishing unit respectively. (2) Use of the morphological characters and otolith weight as a predictor of fishage and growth has proven an accurate and precise method, but so far it mainlyfocused on the fast growing fishes. In this study, belenger’s jewfish (Johniusbelengerii) is presented as a model species, to determine the feasibility andapplication potential for slow-growing species. The discriminant function analysis(DFA) and cross-validation were applied to a series of0,1,2age groups. Theindividuals and classification was based on the shape variables that showed64.1%correct age classification,93.5%correct age classification with inclusion of otolithweight in the discriminant function and84.0%correct age classification forapplication test group. Our finding reveals that the combination method does workwell in belenger’s jewfish and proved its application potential for Sciaenids thatdistributed in coastal waters of China.