Abstract
Seagrass meadows play a key ecological role as nursery and feeding grounds for multiple fish species. Underwater Visual Census (UVC) has been historically used as the non-extractive method to characterize seagrass fish communities, however, less intrusive methodologies such as Remote Underwater Video (RUV) are gaining interest and could be particularly useful for seagrass habitats, where juvenile fish camouflage among the vegetation and could easily hide or flee from divers. Here we compared the performance of UVC and RUV methodologies in assessing the fish communities of two seagrass meadows with low and high canopy density. We found that RUV detected more species and fish individuals than UVC, particularly on the habitat with higher seagrass density, which sheltered more juveniles, especially herbivorous, and adult piscivorous of commercial importance, evidencing significant differences in energy flow from macrophytes to predators between seagrass habitats, and also differences in the ecosystem services they can provide. Considering the ongoing worldwide degradation of seagrass ecosystems, our results strongly suggest that fish surveys using RUV in ecologic and fisheries programs would render more accurate information and would be more adequate to inform the conservation planning of seagrass meadows around the world.
Highlights
Seagrass meadows provide shelter and food resources that sustain high levels of marine biodiversity in complex trophic chains interconnected with adjacent ecosystems such as mangroves and coral reefs[1,2,3,4,5]
2% of studies in the world have used baited Remote Underwater Video (RUV) (BRUVS), relative to 43% of studies on rocky and coral reefs[34], despite that RUV could be useful in seagrass meadows, as many fish are wary juveniles that tend to flee in the presence of the diver and are very good in camouflaging among the vegetation
We identified a total of 63 fish species belonging to 26 families, with RUV recording 48 species of 25 families and Underwater Visual Census (UVC) registering 31 species of 17 families in total
Summary
Seagrass meadows provide shelter and food resources that sustain high levels of marine biodiversity in complex trophic chains interconnected with adjacent ecosystems such as mangroves and coral reefs[1,2,3,4,5]. The most common non-destructive method is Underwater Visual Census (UVC), as it is a low-cost technique, which allows fast data gathering (Supplementary Table S1) This method presents several disadvantages, as it strongly depends on the surveyor skills, water clarity and it is affected by the diver presence, which incites many fish to flee or hide before being recorded[27,28,29]. 2% of studies in the world have used baited RUVs (BRUVS), relative to 43% of studies on rocky and coral reefs[34], despite that RUV could be useful in seagrass meadows, as many fish are wary juveniles that tend to flee in the presence of the diver and are very good in camouflaging among the vegetation These characteristics could reduce the effectiveness of UVC surveys. Both habitats were previously described[35]
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