Genetic identity and length-weight relationships of Indo-Pacific sergeant Abudefduf vaigiensis (Quoy and Gaimard, 1825) from the south-east coast of India

Abstract

Ambiguity regarding the identification of Indo-Pacific sergeant Abudefduf vaigiensis (Quoy and Gaimard, 1825) was sought out through classical taxonomic approach along with molecular confirmation. DNA barcoding of 650 bp region of the Cytochrome C oxidase 1 gene revealed the confirmation of taxonomical identity of the species from the region. Length-weight relationships and relative condition factor in A. vaigiensis were investigated on the samples collected from the south-east coast of India, Gulf of Mannar, to assess the significance of allometric factor and the wellbeing. A total of 360 fishes were collected for the study and categorised into four groups namely males, females , fishes with morphologically undifferentiated gonads (unsexed) and overall pooled samples. Among 360 fishes, 154 were males and 88 were females and the remaining 118 were categorised as unsexed. The analysis was based on fish samples with total length (TL) ranging from 83 to 150 mm and weighing 12.5 to 62.5 g. Length-weight equation and regression coefficient obtained for males, females, unsexed and pooled fishes were W = 0.06 L2.55 (R2 = 0.82); W = 0.02 L2.94 (R2 = 0.88); W = 0.04 L2.68 (R2 = 0.96) and W = 0.04 L2.67 (R2 = 0.92) respectively. The regression parameter ‘b’ obtained in all the cases were below 3, indicating negative allometric relationship of length and weight. Relative condition factor (K) among pooled fishes showed a value above 1, which indicates better condition of fish. The results of the present study showed that the existing hydrobiological conditions of the Gulf of Mannar area were conducive for food availability, free movement, feeding and better growth of the fish. The present study is also the first report on the molecular confirmation of the species from Indian waters and its morphometry from south-east coast of IndiaKeywords: COI sequencing, Indo-Pacific sergeant major, Length-weight relationship, Relative condition factor, South-east coast of India