Studies on Mahshahr Creeks macrobenthos with emphasis on their importance in fish feeding

To study the macrobenthic community at Mahshahr creek four Creeks namely Bihad, Doragh, Ghazaleh and Ghanam were chosen. Sampling was conducted on bimonthly basis and carried out from August 1996 to June 1997, 216 sediment samples were collected from 12 stations using 0.1 m^2 Van Veen Grab, The stations were located at the mouth, middle and the end of each Creek. In situ measurements of temperature pH, DO and salinity were done using different sensors. The samples for the measurements of TOM, grain size were collected and analysed in vitro. The results indicate spatial and temporal heterogeneity in the structure of macro faunal assemblages of the creeks. A total of 12 macrofaunal groups were identified within the study area. Amphipods were the most dominant group (43%) followed by polychaetes (42%), copepods (3.5%), tanaids (3.1%) and other groups (8.4%). The range for the numerical abundance of macrobenthos was between 12583 to 3648 individual per m2 and the variation was done to different bottom texture the variable environment conditions governing the different parts of each creek as well as within creeks. Application of diversity indices (Shannon H and Simpson indices) on the dominant macrobenthic assemblages (crustaceans & polychaetes) was varied between 1 to 2.5 being higher in Bihad and Ghanarn and much reduced Shannon H index or a higher Simpson in Ghazaleh. Probably brought about activities in this creek. Gut content analysis of four species of fish showed that the main food items consist of Crab, Shrimps and other crustacean species, The secondary production of macrobenthic fauna and hence a fish production were assessed. To do this first the production of most dominant species Apseudes sp. was computed through Cohort analysis. The total macrobenthic production was estimated and from this fish production was computed. The macrobenthic and fish secondary productions were 24300 tons/year) and 24300 (tons/year) respectively. These values were lower than those with similar areas in the Indian Ocean.