Evaluation of the trophic status of Sillago sihama and Sillago arabica at the south of Shatt Al-Arab River, Iraq

The present study is investigated the diet composition, feeding activity and intensity, and trophic niche breadth of two Sillaginid fish, Sillago sihama and Sillago arabica at the south of the Shatt Al-Arab River, Iraq from May 2019 to April 2020. A total of 511 specimens of fish comprised of 239 S. sihama and 272 S. arabica were used for the study. Fish length ranged from 11.7-23.7 and 13.0- 31.2 cm of the previous species, respectively. The results showed that the feeding activity and intensity influenced by months since the lowest stomach fullness occurred during the winter months. The analysis of diet for both species using the index of relative importance (IRI %) of prey items showed that the species were carnivores. The prey items of S. sihama were crabs (80.8%), shrimp (14.6%) and fish (4.6%), while the diet of S. arabica composed mainly on crabs (54.3%), shrimp (32.7%) and fish (13.0%). The overall values of feeding and vacuity indices were 40.4% and 9.5%, respectively for S. sihama, whereas 52.0% and 18.2%, respectively for S. arabica. Based on the results of trophic niche breadth indicate that S. schema is a high specialist feeder (Bi= 0.23), while S. arabica was considered a non-specialized feeder (Bi= 0.71). The study concludes that both species were carnivorous feeders, feeding mainly on crabs, shrimp and fish. S. sihama was a low specialized feeder, while S. arabica was not specialized.