engleski

Do lure-assisted underwater visual census (LURE-UVC) and diver- operated video census (DOV) detect similar fish communities, habitat mosaics and species-specific habitat preferences?

Fish communities within two Croatian MPAs were surveyed using both diver-operated underwater video (DOV) via SCUBA and lure-assisted visual census (Lure-UVC) via snorkling. Both methods were applied at similar depths within replicate MPA locations, Kornati NP (4) and Brijuni NP (2). We predicted that the methods detect similar fish communities, habitat mosaics, and fish habitat preferences. To avoid inter-observer variability- errors, fish and habitat identification in all surveys was done by the CK. Habitat types were defined by a common protocol. Higher species richness (35 > 30) was detected by lure-UVC in Kornati. In Brijuni, DOV detected more species (31 > 25). The MPA-specific communities observed by the two methods were 72% similar within Kornati NP and 92% similar within Brijuni NP (Sørensen Index). Both methods recognized the same six habitats in Brijuni NP and five common habitats in Kornati NP, with one unique observed by DOV. In Kornati NP, Lure-UVC detected significant habitat preferences for 10 (28%) species of which nine preferred transitional habitats, the edges between R and U (RU) and R and P (RP) ; DOV detected significant habitat preferences for 15 (50%) species of which 12 preferred either R or RP transitions. In Brijuni NP lure-VC detected four (13 %) and DOV seven (28 %) species with significant habitat preference, and all eleven species were significantly attracted to transitions from rocky reefs to sedimentary bottoms (RU) and all significantly avoided bare sand (U). We conclude that the two methods are comparable in their ability to sample fish communities, habitats and habitat preferences. Decisions about which method to use should focus on availability of resources and target depths. Lure-UVC is more cost and time efficient because it does not need SCUBA and video-processing but requires the presence of a fish/habitat expert in the field, preferably the same individual. DOV requires costly SCUBA operation and lengthy post- video analysis in the lab but allows for multiple experts relying on permanent records. Sample sizes per unit field-time is high for DOV and depends on the number of divers operating DOV. DOV can be applied at wider depth range than surface-based UVC.

fish communities ; diver operated underwater stereovideo ; lure assisted visual census ; Adriatic

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