ابولقاسم روحی

This research is a part of the studies that have been carried out in line with a research plan in Tajen river since 2020-2021. Sampling was done in 7 study stations, including 1) Sari diversion dam, 2) Mahfroz Mehaleh 3) Panbeh Chole 4) Soteh 5) Farah Abad 6) after dam outlet 7) river estuary. The purpose of this research is to investigate the identification, distribution and diversity of fish species and their abundance in different sampling stations. A total of 2,454 fish were examined, belonging to 15 families, 25 genera and 28 species were identified, which include the families Acipenseridae, Atherinidae, Clupeidae, Cobitida, Cyprinidae, Gastrosteidae, Gobiidae, Leuciscidae, Mugilidae, Poecillidae, Percidae, Petromyzonida, Xenocyprididae, Acheilognathidae and Syngnathidae. The largest diversity of species belongs to the Leuciscidae. In this research, the species diversity increased from the upstream to the downstream of the river. According to the Brillion,s index (BI), the lowest BI was in station 3 with 1.415 and the highest in station 7 with 2.989. There was a significant difference in terms of BI in different stations (p<0.05). The average Brillion and Shannon indices obtained in the upstream of the rubber dam were much lower than the downstream of the rubber dam, which shows the effects of the dams on fish communities. The results of this research showed that the diversion dam and the rubber dam as one of the physical and man-made factors have been able to affect the diversity of fish species upstream and downstream of the river, so river restoration is necessary in order to restore anadromous fish stocks.

This study was carried out in line with the Caspian Sea Central Plateau Water Transmission Program in the southern shores of the Caspian Sea and Goharbaran region in 2013-2014. Sampling was carried out monthly at 8 stations at depths of 5, 10 and 15 meters in 2 transects. The purpose of this study was to investigate the relationships between some physico-chemical parameters of water and TOM (total organic matter), distribution, abundance and biomass of different species of Amphipoda in half-lines, depths, stations and seasons. Overall, one species of Niphargoides caspius from the Gammaridae and four species of Stenogammarus similis, Stenogammaus macrorus, Stenogammarus carausuii and Stenogammarus compenus of Pontogammaridae were identified. A total of 15118 individuals of the benthic organisms were counted, in which, S. compresus and N. caspius with 68 and 2 percentages, respectively. Overall, the mean (± standard error) density and biomass of benthic organisms during the period were 128±14.08 ind.m-2 and 0.15±0.01 g.m-2, respectively. According to Spearman test, density of S. carausuii, S. macrorus and S. similis was significantly correlated with sedimentation (sand) (p<0.01). Multivariate cluster analysis based on Spearmanchr('39')s correlation coefficient on the relationship between density and biomass of different species of Amphipoda with some environmental parameters, grain size and total organic matter (TOM) of bed sediments showed that the members of this group belonged to a sand bed and dissolved oxygen are more strongly correlated in which could be due to ecological origin of Amphipoda groups.

This study was carried out at the southeast of the Caspian Sea on the shores of the Goharbaran region during 2013-2014. Sampling was repeated monthly in eight stations. A total of 157 species of phytoplankton, 10 species of zooplankton and 24 species from macro invertebrate were identified. There were significant differences based on abundance and biomass among different biological groups in various stations (p<0.05). Comparing the abundance and density of phytoplankton in different seasons showed that there was an increasing trend in phytoplankton from spring to winter, whereas the abundance and biomass of zooplankton showed a decreasing trend. The results of the multivariate statistical analysis, Pearson correlation coefficient and Principal Component Analysis (PCA) in different months showed that the biomass of phytoplankton and zooplankton had the highest correlation (0.943), whereas the abundance of zooplankton and jelly comb had the highest correlation which could be due to their physiological structure and ecobiological conditions. In conclusion, ecological relationships among biological groups can be due to the abundance and biomass changes, species diversity, environmental parameters, predator, seasonal changes, feeding habits and environmental pollutions.