Developing a DNA barcode library for perciform fishes in the South China Sea: Species identification, accuracy and cryptic diversity.

DNA barcodes were studied for 1,353 specimens representing 272 morphological species belonging to 149 genera and 55 families of Perciformes from the South China Sea (SCS). The average Kimura 2-parameter (K2P) distances within species, genera and families were 0.31%, 8.71% and 14.52%, respectively. A neighbour-joining (NJ) tree, Bayesian inference (BI) and maximum-likelihood (ML) trees and Automatic Barcode Gap Discovery (ABGD) revealed 260, 253 and 259 single-species-representing clusters, respectively. Barcoding gap analysis (BGA) demonstrated that barcode gaps were present for 178 of 187 species analysed with multiple specimens (95.2%), with the minimum interspecific distance to the nearest neighbour larger than the maximum intraspecific distance. A group of three Thunnus species (T. albacares, T. obesus and T. tonggol), a pair of Gerres species (G. oyena and G. japonicus), a pair of Istiblennius species (I. edentulous and I. lineatus) and a pair of Uranoscopus species (U. oligolepis and U. kaianus) were observed with low interspecific distances and overlaps between intra- and interspecific genetic distances. Three species (Apogon ellioti, Naucrates ductor and Psenopsis anomala) showed deep intraspecific divergences and generated two lineages each, suggesting the possibility of cryptic species. Our results demonstrated that DNA barcodes are highly reliable for delineating species of Perciformes in the SCS. The DNA barcode library established in this study will shed light on further research on the diversity of Perciformes in the SCS.

[Applying multi-model inference to estimate growth parameters of greater lizard fish Saurida tumbil in Beibu Gulf, South China Sea].

Age and growth parameters are key parameters in fish stock assessment and management strategies, thus it is crucial to choose an appropriate growth model for a target species. In this study, five growth models were set to fit the length-age data of greater lizard fish Saurida tumbil (n = 2046) collected monthly from December 2006 to July 2009 in the Beibu Gulf, South China Sea. The parameters for each model were estimated using the maximum likelihood method under the assumption of the additive error structure. Adjusted coefficient of determination (R2adj), root mean squared error (RMSE), Akaike's information criterion (AIC), and Bayesian information criterion (BIC) were calculated for each model for fitness selection. The results indicated that the four statistical approaches were consistent in selection of the best growth model. The MMI approach indicated that the generalized VBGF was strongly verified and made up 95.9% of the AIC weight, indicating that this function fitted the length-age data of the greater lizard fish well. The growth function was Lt = 578.49 [1-e -0.05(t-0.14) 0.361.

[Feeding habits of Trichiurus lepturus in Beibu Gulf of South China Sea].

From August 2008 to September 2009, the feeding habits of Trichurus lepturus L. in Beibu Gulf of South China Sea were studied by monthly sampling and stomach content analysis. In study area, T. lepturus was euryphagous, which fed on fish, cephalopoda, benthic crustacean, and zooplankton, etc., among which, Bregmaceros rarisquamosu, Decapterus maruadsi, and Acetes chinensis were the main prey components, accounting for 37.99%, 16.42%, and 10.03%, respectively. D. maruadsi and Anchoviella heteroloba appeared throughout the Beibu Gulf all year round, and could be served as the index species for the migration and fishing ground distribution of T. lepturus. The indices feeding intensity and stomach fullness differed significantly among seasons (P < 0.001); while the index prey diversity had no significant seasonal difference (P > 0.05), which peaked in autumn and had an annual average value of 1.97. Cluster analysis revealed that when the preanal length of T. lepturus was 190 mm, i. e., at 50% of maturity length, a clear diet shift happened, from small zooplankton, pelagic fishes, and crustacean for the juveniles to predominantly larger fish and cephalopoda for the adults.