Investigating the relative importance of the organic matter of mangrove tree Avicennia marina in the feeding of small carp Ilisha melastoma (Bloch & Schneider, 1801) in the mangrove biosphere reserve; Stable isotope approach

The purpose of this research is to investigate the relative importance of Avicennia marina organic matter in the feeding of Ilisha melastoma fish in the Mangrove Biosphere Reserve; It was stable isotope approach. Three primary food sources including mangrove tree leaves, microphytobenthos and suspended organic particles were analyzed isotopically. The samples of primary food sources and fish are converted into pure and simple gases such as CO, CO2 and N2 after minimizing the size and turning into powder. Then the identified isotope ratios are compared with a measured standard and the exact amount of isotope formed in the sample is obtained. In this research, sampling was done seasonally in August in the summer season and February in the winter season of 2019 in the mangrove ecosystems of Bandar Khmer, Hormozgan province.In the summer season, the average stable carbon isotope of primary food sources fluctuated from -28.07 units per thousand for mangrove leaves to -13.58 units per thousand for microphytobenthos.This average in the winter season was obtained from -28.05 units per thousand for mangrove leaves to -13.54 units per thousand for microphytobenthos.The average stable nitrogen isotope of primary food sources in the summer season fluctuated from 1.44 units per thousand for microphytobenthos to 10.72 units per thousand for suspended organic particles.The results of this research showed that in the summer season, suspended organic particles with 63% and in the winter season, microphytobenthos with 45% play the most important role in providing the food needed by the small shemsk fish.