Trophic Level Estimation in Different Marine Aquatics With Emphasis on TrophLab (Persian Gulf and Oman Sea)

The estimation of fractional trophic levels is essential for the management of fisheries resources as well as for quantifying the ecosystem effects of fishing. The main aim of this study was estimation of trophic levels in different marine organisms using TrophLab software in the Persian Gulf and Oman Sea. We gathered all available information on diet that has been locally described. Usable diet data of 25 species resulted in 28 trophic level estimates that ranged from 2.28 to 4.50. For those fishes with more than one dietary study estimation of trophic level was found to vary, probably due to a combination of different size ranges, with bigger fish tending to have higher trophic levels. The maximum trophic levels were obtained for Euthynnus affinis, Sphyraena putnamae, Thunnus tonggol and Thunnus albacores with amount of 4.50, 4.50, 4.49 and 4.45, respectively. An ordinary regression model relating trophic level and body length was formulated. Result showed that trophic level and body length were moderately correlated. This is the result of the fact that as fish grow their relative success rates increase due to ontogenetic changes in sensory and swimming capacities. Trophic level and regression model should be of help in the formulation of trophic indicators and models marine ecosystems.