Determining appropriate site for releasing hatchery-reared juvenile fish using macrobenthos diversity indices - a case study in Gorganroud river

The aim of this research conducted in the lowermost (lowest) zone of Gorganroud river - southeastern Caspian Sea, in where hatchery-reared juvenile fish were released for stock enhancement, was Determining appropriate site for releasing hatchery-reared juvenile fish using macrobenthos diversity indices. Sampling was undertaken over five surveys, (spring 2018, spring, summer, and autumn 2019 and winter 2020), in three sites (with three replications) including (1) boarder guard station (BGS), (2) Khaje Nafas bridge (KNB), and (3) Khaje Nafas dam (KND). The results of split plot analysis showed that no significant difference was observed in sedimentary organic matter among sampling sites. Biodiversity indices and water physico-chemical factors also showed significant differences among sampling sites, as indices like abundance, species richness and Shannon index in KNB site were significantly higher than those in BGS site  (in where reared juvenile fish were released for stock enhancement). In addition, water quality was significantly better in KNB site (p<0.05), as water in BGS site had significantly higher dissolved oxygen (Do) and lower salinity and total dissloved solid (TDS) than that in BGS site. Thus, it is recommended reared juvenile fish be released in more suitable places (ie., site 2) to increase the survival probability of released juvenile fish.