Research Article: Seasonal variations in diet and feeding habits of Saurida tumbil (Bloch, ۱۷۹۵) , Netuma thalassina (Rüppell, ۱۸۳۷) and Pomadasys kaakan (Cuvier, ۱۸۳۰) in the northern coasts of the Oman Sea

The aim of the present study was to explore seasonal variations in the diet of Saurida tumbil, Netuma thalassina and Pomadasys kaakan in the Iranian coasts of Oman Sea during ۲۰۱۸-۲۰۱۹. These abundant fishes share same habitats in the Oman Sea .Diet analysis including frequency of occurrence of prey, feeding intensity index, the index of empty stomachs and length weight relationship for ۱۱۶۶ individual were calculated.Based on Gastrosomatic (GaSI) and vacuity index, the maximum feeding intensity was noticed for S.tumbil and P. kaakan during post monsoon and for N. thalassina in pre monsoon time. S. tumbil showed the lowest GaSI index and the highest empty stomachs in monsoon.The findings of food composition indicated remarkable dietary overlap between species in this research, especially between N. thalassina and P.kaakan on decapods , gastropods and fishes (dominant prey) during all seasons. For S. tumbil, the most important prey items were fishes, following, cephalopod and penaeidae and it was determined that the feeding intensity of P. kaakan and N. thalassina could not be altered by monsoon but  remarkable seasonal  variation was noticed in their diet composition contents. The results showed that the pre-monsoon, monsoon and post-monsoon periods have significant effects on the diet composition of all three species under study, which could be explained by changes in resource abundance, availability and diversity of prey.  

Keywords:

Feeding intensity , Food composition , Monsoon , Oman Sea