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Abstract.  The coastal fish assemblage in three protected sites and one unprotected area in the Slovenian part of the Gulf of Trieste (Northern Adriatic) was studied. Species composition and richness were comparable at all studied sites, including the control, unprotected area. Differences in fish density between the protected area of Debeli rtič and the unprotected area of Fiesa‐Pacug were revealed using correspondence analysis. Particularly the densities of certain labrid species (Symphodus cinereus and S. roissali) were higher in the protected area. Those differences are attributable to the extended and densely vegetated infralittoral belt of the Debeli rtič area rather than to its protected status.

The global decline of brown algal forests along rocky coasts is causing an exceptional biodiversity loss. Regardless of conservation efforts, different techniques have been developed for large-scale restoration strategies in the Mediterranean Sea. In this study we tested ex situ pilot restoration of Gongolaria barbata (=Treptacantha barbata) for the first time in Slovenian coastal waters. Healthy apical fronds of the species were collected and the development of recruits on clay tiles was followed under laboratory conditions for 20 days. Despite the experimental difficulties experienced, especially due to the lack of antibiotics to prevent the growth of the biofilm, G. barbata recruits were outplanted in the sea on two concrete plates with 48 tiles each, protected by purpose-built cages to avoid grazing by herbivorous fish. The high survival rate of juveniles after four months in the field (89% of the tiles on the plate that was constantly protected) suggests that outplanting G. barbata is an operable approach for restoration efforts in the northern Adriatic Sea. Our first experiment in Slovenian coastal waters provides new information for the optimization of the best practices during the laboratory cultivation and addresses the early steps of restoration and introduction of young thalli in the natural environment.

Mollusc assemblages associated with Cystoseira associations were sampled in the southern part of the Gulf of Trieste during the summers of 2008 and 2012. Samples were collected by SCUBA diving in the infralittoral belt (from 1 to 4 m depth). The surface within frames of 20 x 20 cm was scraped off with samples were collected by hand or with an air-lift sampler. Four erected algal species were found: Cystoseira barbata, C. compressa, C. corniculata and Halopithys incurva. A total of 69 species of molluscs were identified in those associations. Gastropoda were dominant, with the highest species richness and abundance, followed by Bivalvia and Polyplacophora. A large number of juveniles were found, proving the importance of Cystoseira associations for mollusc recruitment. Differences in composition, structure and abundance of mollusc assemblages were found for sites dominated by different algal species, and correspond to different morphology and degree of development of canopy-forming species. The present study confirms that the dominant algal species within Cystoseira associations strongly influence, although at different levels, abundance and distribution of mollusc assemblages in the Northern Adriatic Sea.

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