Diets of Halfbeak Hemiramphus lutkei (Valenciennes, 1847) from Karachi Coast, Pakistan

Objective: To investigate the diets of the Lutke’s halfbeak, Hemiramphus lutkei (H. lutkei) to determine the food and feeding habits. Methods: Samples of H. lutkei were collected from the landing sites of Karachi Coast, Pakistan. Total length was measured to the nearest 0.01 cm using digital slide calipers, and total body weight was measured using an electronic balance with 0.01 g accuracy. The dietary composition was determined from gut content examination and analysis was done using frequency of occurrence and numerical methods. To assess the changes in diet with size, H. lutkei were divided into two size groups, Group 1: 14-20 cm (n=250) and Group 2: 21-25 cm (n=160). Results: The total length and body weight of the sampled specimens ranged from 14 to 25 cm and 10 to 23.5 g, respectively. Out of the studied specimens, 45.12% fish stomachs were found to be empty. Dietary composition revealed daphnia, small fish, isopods, unidentified animal materials, ostracods and unidentified plant materials in the gut contents of Lutke’s halfbeak. Therefore, H. lutkei is omnivore fish feeding on algae, zooplankton, small fishes and different food items of both plant and animal origin. According to the Schoener overlap index (C), there was no significant difference in feeding of the two length groups of H. lutkei (C=0.833). On the other hand, the Shannon-Wiener index showed that the prey diversity of the Lutke's halfbeak in Group 1 was lower (H / =1.545) than that of Group 2 (H / =1.653).