Relative Gut Length and Gastro-somatic Index of Acanthopagrus arabicus (Iwatsuki, 2013) from the Offshore Waters of Pakistan

Abstract

Relative gut length, Zihler’s index, and Gastro-somatic index of Acanthopagrus arabicus were studied to investigate its feeding intensity and feeding habit, by collecting 240 samples of fishes from two fishing harbors of Pakistan from September 2017 to August 2018. According to the results, fish mean total length ranged from 16.26 ± 2.83 cm (in June) to 30.89 ± 5.16 cm (in September), and mean total weight ranged from 77.70 ± 42.25 g (in June) to 486.80 ± 237.28 g (in November). The total length and gut length of A. arabicus have a strong statistical relationship (P < 0.05). In A. arabicus, the overall relative gut length (RGL) values were ranged from 0.69 to 2.63 with a mean value of 1.57 ± 0.31. The RGL lowest (1.35) and highest (1.70) value was analyzed in the size groups ranging 12.0 - 16.0 cm TL and 24.1 - 28.0 cm TL respectively. However this value is not much greater than 1, A. arabicus could be described as an omnivorous feeding habit in coastal waters of Pakistan. The temporal changes in the feeding intensity of A. arabicus were found as the Gastro-somatic index (Ga-SI) presented a significant difference during the twelve months (ANOVA, P < 0.05). The Gastro-somatic index lowest value was found in January (1.55 ± 0.59) and highest in August (5.66 ± 3.26). This type of study is beneficial for aquaculture as well as assessing the ecological role of A. arabicus along with its position in the food chain of Pakistani coastal waters.