Using off-the-shelf GPS loggers to assess co-occurrence between marine mammals and small-scale fisheries: a pilot study from the Mediterranean Sea

Abstract

Fisheries constitute a major threat to marine mammals globally. To evaluate the impact of small-scale fisheries (SSF) on regional under-studied marine mammal populations, we tested a novel and cost-effective approach at three data-limited locations of the central and eastern Mediterranean Sea. Using off-the-shelf GPS loggers to track SSF activities and systematic surveys to map the distribution of marine mammals, we assessed the probability of co-occurrence between SSF and marine mammals by reporting areas of spatial overlap. Spatial overlap between SSF and the core zones of marine mammal distribution (ranging between 21.85–35.4%) was observed in all three locations, indicating potential interaction hotspots. The probability of co-occurrence in those areas varied from 0.5–2.9% depending on the species. The resulting overlap between fishing activity and marine mammals may pose a threat in both directions: higher risk of species entanglement and economic burden on fishers due to gear damage. Despite the spatial and temporal limitations of this pilot study, the proposed approach can provide baseline information on SSF-marine mammal co-occurrence, particularly in financially limited regions. If applied on a larger scale, our method may be used to inform future conservation actions with the aim to reduce pressure on key populations.

Whales and dolphins of the Adriatic Sea

“…Land-and boat-based surveys in Montenegro in 2016-2019 suggested that distribution hotspots for bottlenose dolphins were located within ~16 km from the coast, while a similar study conducted in Albania in 2018-2019 indicated a higher occurrence within ~6 km from the coast; in both areas dolphins were reported to prefer waters shallower than 200 m (Glarou et al, 2022).…”

“…While the distribution of bottlenose dolphins in the Adriatic Sea frequently overlaps with small-scale fisheries deploying gill and trammel nets (e.g. in the northern Adriatic; Genov et al, 2008, and in southern Montenegro and northern Albania; Glarou et al, 2022), information on these interactions is rarely based on direct observations.…”

“…Observations from passenger ferries, conducted between 2015 and 2018 in the central and southern sectors of the Adriatic, totalled 31 sightings of striped dolphins in waters 79-1,167 m deep (Azzolin et al, 2020). Boat-and land-based surveys in the waters of Montenegro, between 2016 and 2019, totalled three sightings: one in waters shallower than 200 m and two in deeper waters (Glarou et al, 2022).…”