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Ichthyofauna of the salt marsh Palud – Palù (Istria, Croatia) - summer aspect

Special ornithological reserve Palud – Palù is a saltmarsh wetland of antropogenic origin located on the west coast of Istria near the sea, about 8 km southeast of Rovinj. This important part of protected areas in Istria covers about 18 ha and is one of the few remaining coastal wetlands on the eastern Adriatic coast. This natural depression has turned into a wetland due to the rainwater inflow from the surrounding area and springs in the northern part. It is connected to the sea by the Austro-Hungarian army in 1906 by digging a 200-m canal in order to prevent the development of mosquito larvae that were carriers of malaria by increasing the salinity of the water. As result the wetland has become more brackish, and over time increasingly saline to its current hypersaline state (> 45 ppt). Wetland is a very valuable habitat primarily for wading birds as a nesting, resting and feeding area during migrations. The analysis of the available data shows no systematic and comprehensive research of ichthyofaunistic values. During the project "CREW – Coordinated Wetland Management in Italy – Croatia Cross Border Region" (Project ID: 10044942) a preliminary inventory of fish fauna was made. Sampling of fish was performed during July and August 2021. In the study of the composition, biomass and structure of fish communities, experimental fishing was performed using small coastal seine nets, hand nets and fish traps. The presence of 6 species has been recorded ; 3 from the family Mugilidae – Mugil cephalus, Chelon saliens and Chelon auratus, as well as Sparus aurata, Gambusia sp. and Anguilla anguilla. Gambusia was the most numerous with 67% in the total number of catches, followed by Ch. saliens (18.77%), M. cephalus (9.83%), Ch. auratus (4.34%), while A. anguilla and S. aurata were presented with 0.12%. Juvenile stages predominated in the fish communities of mullets indicating wetland as important feeding and nursery habitat. Record of A. anguilla is rare finding of this species in such saline habitat conditions on the eastern Adriatic coast. Although there are few species, the wetland ichthyofauna is of dynamic composition since the mullet populations show periodic day – night migrations to the sea, while gambusia is a permanent resident. In a broader ecological sense, although the composition of fish communities in the wetland is not natural, it is of special importance for the ichthyophage bird fauna and as such is necessary to maintain their nesting and migrating populations.

hypersaline conditions, fish communities, changing environmental conditions, Mugilidae

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