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

Abstract

Introduction: 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.
Materials & Methods: 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).
Result: 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.
Conclusion: 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.