Biological aspects of the Indo-Pacific sergeant Abudefduf vaigiensis (Quoy and Gaimard, 1825) from Gulf of Mannar, Tamil Nadu, India

Abstract

Food and feeding habits of the commercially important marine ornamental fish Abudefduf vaigiensis from the Gulf of Mannar were evaluated. Analysis of gut contents indicated that A. vaigiensis is an omnivorous fish, feeding on any available food item in its environment, such as seaweeds, cladocerans, copepods and insects. Most of the sampled fishes had either quarter-full or half-full or three-fourth full stomachs. The index of preponderance indicated seaweeds as the preferred food item among majority of length classes except for those falling within the 80-89 and 100-109 length classes, in which a preference towards copepods was observed. On a monthly basis, seaweed Spongomorpha sp. emerged as the predominant food item. Gastro-somatic index (GaSI) for males recorded the highest value in July (1.20) and lowest (0.36) in November, while that of females recorded the highest value in July (0.95) and lowest value (0.47) in January. Hepato-somatic index (HSI) of females recorded the highest in December (2.01) and lowest in July (0.83), while that of males recorded the highest value in January (1.25) and lowest in September (0.81). Gonadosomatic index (GSI) in females recorded maximum in February (4.23) and lowest in June (1.32) while that of males recorded the highest value in February (0.85) and lowest value in July (0.35). The results of the study indicate that adopting seasonal regulatory measures is essential for sustainable exploitation of the species, since their trade relies on wild collection. The study also revealed a negative correlation between the feeding patterns of these fish and their reproductive development.

Keywords: Abudefduf vaigiensis, Feeding intensity, Gastro-somatic index, Gonadosomatc index, Hepato-somatic index