Monitoring marine fishes using underwater video techniques in the Mediterranean Sea

Rev Fish Biol Fisheries https://doi.org/10.1007/s11160-023-09799-y REVIEWS Monitoring marine fishes using underwater video techniques in the Mediterranean Sea Melina Nalmpanti · Anna Chrysafi · Jessica J. Meeuwig · Athanassios C. Tsikliras Received: 8 December 2022 / Accepted: 2 August 2023 © The Author(s) 2023 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 fishrelated studies in the Mediterranean basin. The most common technique used in the Mediterranean Sea Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s11160-023-09799-y. M. Nalmpanti (*) · A. Chrysafi · A. C. Tsikliras Laboratory of Ichthyology, Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece e-mail: ; A. Chrysafi e-mail: A. C. Tsikliras e-mail: A. Chrysafi Q-PLAN International, 11 El. Venizelou Str, Kalamaria, 55133 Thessaloniki, Greece 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. Keywords Review · Non-destructive methods · Sampling · ROV · RUV · BRUV J. J. Meeuwig Marine Futures Lab, School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia e-mail: Vol.: (0123456789) 13 Rev Fish Biol Fisheries Introduction Fish monitoring underpins conservation and management and is particularly critical given the declining biomass trends that characterize many commercial fish species worldwide (Costello et al. 2012; Palomares et al. 2020). Fish monitoring can utilize either fishery-dependent (commercial or recreational) or fishery-independent data. Fishery-independent techniques include experimental fishing (Priester et al. 2021), remote sensing (Santos et al. 2000), acoustic surveys (Rountree et al. 2006), telemetry (Hammerschlag et al. 2011), underwater visual census (Samoilys and Carlos 2000), genetics (Blower et al. 2012) and underwater video (Mallet and Pelletier 2014). The use of non-destructive and non-extractive techniques, such as those based on video, is particularly desirable in Marine Protected Areas (MPAs) in order to maintain the integrity of the ecosystem and avoid placing further pressure on fish populations (Collie et al. 2000; Sciberras et al. 2018; Murphy and Jenkins 2010). Underwater video use in ecological studies mainly aims to monitor fish populations (Marra et al. 2016), study the behavior of fish (Ajemian et al. 2016) or develop and compare methodologies (Stobart et al. 2007). The first underwater video system for biological studies was described in 1952 (Barnes 1952) and since then, underwater video has become an increasingly popular ecological tool due to its versatility and the technological advances during the last two decades (Mallet and Pelletier 2014). In the Mediterranean Sea, the first underwater video study was conducted in late 1970s (Fedra and Machan 1979) with a rapid increase in the use of underwater video after 2000. Most underwater video techniques, in contrast to Underwater Visual Census (UVC), enable scientists to sample without time and depth limitations and reach locations inaccessible to divers (Cappo et al. 2007; Unsworth et al. 2014). Video-based methods provide a permanent record of standardized replicates with detailed optical view, which minimizes observer bias regarding species identification, fish length estimates and sample unit area (Langlois et al. 2010; Unsworth et al. 2014). Moreover, sampling can be performed by non-taxonomy experts and video footage can be examined several times and by different observers in the lab (Langlois et al. 2010). Contrary to fisheries-based methods and experimental fishing, Vol:. (1234567890) 13 video techniques also provide information on habitat (Collins et al. 2017) and animal behavior (Ayma et al. 2016) and are less selective in terms of species and sizes (Murphy and Jenkins 2010). The use of video techniques is however constrained under poor visibility conditions (Sward et al. 2019) and the presence of bait in baited camera systems may introduce unnatural behaviours (Harvey et al. 2007). When bait is used, the area extent from which fish are drawn is unknown and thus, abundance is relative rather than a real estimate (Heagney et al. 2007). Underwater video-based fish studies can utilize a range of methodologies, depending on the study objectives and available resources. Underwater video equipment can be permanently or temporarily deployed, in shallow water or abyssal depths, powered by batteries or cable, stationary or deployed along transects, and target pelagic or benthic habitats. Systems may be deployed with single cameras or in stereo-configuration to allow length measurements. Worldwide, commonly used methods include the remote underwater video technique (RUV), baited remote underwater video (BRUV) systems, remotely operated vehicle (ROV), diver operated video (DOV) systems and towed video (TOWV) Techniques. Remote underwater video (RUV) systems consist of a video recording device being placed underwater, on the seafloor or in the water column, and do not require human presence to operate. The systems can be set by a diver or deployed from a vessel (Mallet and Pelletier 2014) and can be either linked to a monitoring station by cable (Aguzzi et al. 2011), usually used for long term monitoring, or deployed autonomously operating by battery power (Galasso et al. 2015). Bait can be placed optionally in front of the mounted camera(s) creating an odor plume in order to attract organisms from a broader area, in which (...truncated)