As the development of large-scale offshore wind farms (OWFs) amplifies due to technological progress and a growing demand for renewable energy, associated footprints on the seabed are becoming increasingly common within soft-bottom environments. A large part of the footprint is the scour protection, often consisting of rocks that are positioned on the seabed to prevent erosion. As such, scour protection may resemble a marine rocky reef and could have important ecosystem functions. While acknowledging that OWFs disrupt the marine environment, the aim of this systematic review was to examine the effects of scour protection on fish assemblages, relate them to the effects of designated artificial reefs (ARs) and, ultimately, reveal how future scour protection may be tailored to support abundance and diversity of marine species. The results revealed frequent increases in abundances of species associated with hard substrata after the establishment of artificial structures (i.e., both OWFs and ARs) in the marine environment. Literature indicated that scour protection meets the requirements to function as an AR, often providing shelter, nursery, reproduction, and/or feeding opportunities. Using knowledge from AR models, this review suggests methodology for ecological improvements of future scour protections, aiming towards a more successful integration into the marine environment.
Vessel noise is a primary driver of behavioural disturbance in cetaceans, which are targeted during whale-watch activities. Despite the growing, global effort for implementing best-practice principles, to date, there are no regulations on whale-watch vessel noise levels. Here, we test the hypothesis that a whale-watch vessel with a low noise emission will not elicit short-term behavioural responses in toothed whales compared to a vessel with a louder engine. We measured behavioural responses (n = 36) of short-finned pilot whales (Globicephala macrorhynchus) to whale-watch vessel approaches (range 60 m, speed 1.5 kn). Treatment approaches with a quieter electric engine (136–140 dB) compared to the same vessel with a louder petrol engine (151–139 dB) (low-frequency–mid-frequency weighted source levels, re 1 µPa RMS @ 1 m) were examined. Focal whales were resting mother and calves in small group sizes. During petrol engine treatments, the mother’s mean resting time decreased by 29% compared to the control (GLM, p = 0.009). The mean proportion of time nursing for the calf was significantly influenced by petrol engine vessel passes, with a 81% decrease compared to the control (GLM, p = 0.01). There were no significant effects on behaviour from the quieter electric engine. Thus, to minimise disturbance on the activity budget of pilot whales, whale-watch vessels would ideally have source levels as low as possible, below 150 dB re 1 µPa RMS @ 1 m and perceived above ambient noise.
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.
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