The structure of the infralitoral fish community in the protected area of the Lastovo and Mljet islands

Abstract

Analizirana je struktura nekto-bentičke zajednice riba i njen odnos sa staništem u infralitoralu zaštićenog područja Lastovskog otočja i otoka Mljeta, što je prvo istraživanje takvog tipa na tom području. Vizualnom aproksimacijom bilježen je tip i kompleksnost staništa. Parametri zajednice riba prikupljeni su metodom vizualnog cenzusa na 168 transekata na 31 postaji, te na sedam tipova staništa. Staništa su u obradi podataka sažeta u četiri osnovna tipa: (i) staništa zajednice infralitoralnih algi, (ii) staništa zajednice infralitoralnih algi s manjim naseljima posidonije, (iii) staništa podjednakog omjera algi i posidonije i (iv) staništa naselja posidonije s manjim dijelovima zajednice infralitoralnih algi. Utvrđena je povezanost tipa staništa sa strukturom zajednice riba. Broj vrsta, brojnost i biomasa najviši su u staništima zajednice infralitoralnih algi s manjim naseljima posidonije, a najmanji na staništima većinski prekrivena posidonijom. Nije dokazan utjecaj kompleksnosti staništa na strukturu zajednice. Ovo istraživanje pruža osnovu za buduće procjene učinkovitosti zona potpune zabrane ribolova, koje su planirane u istraživanim morskim zaštićenim područjima. Procjene će biti moguće jer je odabir kontrolnih postaja dobar za većinu postaja unutar NP Mljet koji će biti unutar zona potpune zabrane ribolova. Većina kontrolnih postaja odgovara staništem i strukturom zajednice riba postajama u budućim zonama zaštite.The structure of the necto-benthic fish community and its relationship with habitat features was investigated for the first time by visual census in the protected area of the Lastovo Islands and the island of Mljet. Habitat type and rugosity were recorded by visual approximation. Fish assemblage data were collected by the method of underwater visual census on seven habitat types, which were summarized into four basic habitats for data analysis: (i) infralittoral algae communities, (ii) infralittoral alge with posidonia paches, (iii) half ratio of algae and posidonia and (iv) posidonia meadows with infralittoral algae patches. The structure of the necto-benthic fish community corresponed to a certain level to the habitat type. The highest species richness, abundance and biomass was recorded at the habitats of the infralitoral algae community with patches of posidonia, at the same time the smallest was recorded in the posidonia meadows. Influence of the habitat rugosity was not proven to affect the structure of the fish community. This study provides a basis for assessing the effectiveness of the „no-take“ zones planned in the investigated marine protected areas. Assesments of effectivness will be possible because the selection of control stations has been positively evaluated for most stations within NP Mljet planed for the "no-take" zone. Most control stations were similar in habitat and current qualitative and quantitative fish structure as stations in future „no-take“ zones