engleski

Association of fish and invertebrates with shallow benthic habitats (seagrass, algae, unvegetated) revealed by DGPS/video-tracking dive transects

Fish and invertebrate assemblages associated with seagrass meadows (Zostera marina, Nanoostera noltii, Cymodocea nodosa), rocky-algal communities (Cystoseira), and sedimentary bottoms of various particle sizes (mud, sand, gravel) were investigated in two locations within the Novigrad Sea, a relatively shallow enclosure of the central Croatian Adriatic. Whereas one location is impacted by various anthropogenic disturbances associated with residential housing and tourism, heavy small boat traffic, and various marina and beach constructions, the other location is largely unaffected by anthropogenic disturbances. Utilized was a novel visual census method, which minimizes the well-known problems associated with strip transects and maximizes statistical power per unit effort. Long (ca. 200 m) transects of variable-direction, with video assisted habitat-tracking, DGPS tracking, and depth sounding, allowed for the recording of fish and invertebrate observations simultaneous with various habitat characteristics, as well as geographical location and water depth. Significant positive and negative associations of fish and invertebrate species with specific habitat types were found. Rocky-algal communities were found to have higher fish diversity than seagrasses and unvegetated habitats and all habitats exhibited diurnal variability. Furthermore there were significant differences in macrophyte coverage and faunal diversity comparing the two study locations. The presented study uses a novel, non-destructive, effort and cost efficient method that is highly suitable to elucidate the impact of anthropogenic activities on local abundance and diversity of fish and invertebrates. Therefore it provides a good basis for managing the benthos of targeted populations of fish and invertebrates.

benthic habitats ; seagrasses ; fish assemblages ; DGPS dive transects

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