engleski

What are the synergistic effects of interannual environmental changes and habitat modifications on juvenile fish communities?

Continuous embankment has been reported in recent decades along the Adriatic coast. In the same time, environmental changes associated with warming and climate change are evident throughout Mediterranean. Further on, a signs of high fishing pressure are recognized and highlighted on the European level. The eastern Adriatic coast characterised by numerous bays, coves and lagoons represent at the same time a mosaic of different nurseries for a great number of fish species. In the present study, the multivariate analysis was conducted to elucidate the interannual changes of new settlers’ occurrence and abundance in different nurseries in relation to interannual environmental differences and habitat degradation due continuous embankment. With that aim, fishing, trophic and taxonomic composition and structure of the community data were analysed. Sampling included sites from estuaries to marine coves and statistically significant interannual differences in temperature were found but not in salinity. However, defined groups expressed significant difference in fish abundance and species richness related to the significant difference in salinity and temperature for the same consecutive years. Settler’s delay or retention due negative temperature deviation in spawning period is primarily linked to the northern estuarine nurseries that are under greater coastal influence. Pure marine nurseries at south were less sensitive to interannual temperature fluctuations and mostly defined by salinity influence. The observed community changes in species composition were probably governed by the same pattern since they are reported for specific nursery type. Moreover, the species that mostly contributed to the observed changes were non- commercial, small, benthic resident fishes or those associated with canopy alga for shelter and feeding. The results suggested that major sifting in juvenile fish communities can be expected if the spring is cold and rainy (like in 2019) when late settlement and longer retention of specific fish species were determined due to negative temperature deviation in the spawning period, particularly at the nurseries located in the northern transitional waters that are under a stronger coastal influence and characterised by constant embankment process and marine infrastructure construction. These shifts can have ecological consequences on the population dynamics and inter- and intraspecific relationships within specific nursery ‘communities and for sure can influence recruit year-class strength and therefore have a serious impact on fisheries.

environmental changes, habitat modifications, fish juveniles, nurseries

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