Monitoring marine fishes using underwater video techniques in the Mediterranean Sea

Abstract

The use of underwater video techniques has expanded rapidly in ecological studies and is particularly desirable in protected areas since the method does not impact the habitat or remove fish. The Mediterranean Sea is a biodiversity hotspot under high anthropogenic pressure and consequently, non-destructive and non-extractive techniques for fish monitoring are advantageous. Here, we review 110 publications that used underwater video in fish-related studies in the Mediterranean basin. The most common technique used in the Mediterranean Sea was Remotely Operated Vehicles (ROV) (33%), followed by Remote Underwater Video (RUV) systems (20%), Diver Operated Video (DOV) systems (20%) and Baited Remote Underwater Video (BRUV) systems (19%). Approximately one third of the studies used an additional sampling method, such as fisheries-based or molecular methods with the aim to compare the surveying effectiveness or produce complementary data. The most frequent objectives of the reviewed studies were related to fish community structure, i.e., focusing on community wide metrics such as abundance and biodiversity, or behavioral analyses, while the most commonly studied environments were those of the western Mediterranean and shallow waters, usually involving sandy or rocky reef habitats. Sampling protocols differed widely among studies with transect lengths, soak times and baits all varying. Future research should focus on the least studied parts of the region, such as the eastern and southern Mediterranean Sea and deep-sea habitats. Finally, the development of standardized sampling protocols is recommended to ensure that data are comparable among studies.