Abstract
Coralligenous habitat is considered as one of the most important special habitat types in the Mediterranean; however, due to its inaccessibility, little is known about it, although it is considered as one of the Mediterranean’s richest habitats in terms of species. Due to a low number of studies, it was presumed that the richness of coralligenous fish assemblages is underestimated using traditional visual census methods which are not applicable to the deep, steep, and vertical slopes of coralligenous cliffs and do not capture exhaustively cryptobenthic species commonly found in this habitat. This paper aims at producing a more complete assessment of fish assemblages on a coralligenous cliff by combining different methods, particularly the deep vertical transect visual census and square with anesthetics method. A total of 76 fish species were recorded on a single coralligenous cliff, supporting the opinion that coralligenous cliffs are important Mediterranean biodiversity hotspots. The analysis of species traits between species recorded by the different methods showed how complementary they are to better describe species compositions. Hence, the result of this study demonstrates that the combined use of methods is essential for a more exhaustive description of the whole fish community structure and for accurate estimates of the abundance and diversity patterns, particularly in complex habitats such as coralligenous cliffs.
Highlights
The species recorded by the deep vertical transect (DVT) method and square with anesthetics method (SAM) show a significant difference in all species trait compositions (Table 3)
The DVT species composition was significantly different from the SAM method in relation to the reef, with 11 occasional species recorded, while none of the occasional species were found by SAM (Table 3)
The DVT recorded species had significantly different trophic levels than the SAM recorded species, having more omnivorous and herbivorous species than SAM, as well as species with a trophic level above 4, suggesting a wider trophic range, the modal value for both groups was at 3–3.99 (Table 3)
Summary
The marine environment is extraordinarily diverse and made up of a large number of different marine habitats. A large portion of the ocean remains unexplored, even the coastal habitats, benthic assemblages thriving from 20 m depth down to the end of the continental shelf. Their distribution, ecological roles, threats, and status remain poorly known. A typical Mediterranean habitat includes various coralligenous formations. Due to their inaccessibility, little is known about coralligenous habitats; they are considered as one of the Mediterranean’s richest habitats in terms of species [1]. The ecological importance of coralligenous habitats and their scientific and biodiversity interest is recognized by international conventions (e.g., Barcelona Convention); they can be considered one of the most important “special habitat types”
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