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- Glarou, Maria, et al.
(author)
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Estimating body mass of sperm whales from aerial photographs
- 2023
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In: Marine mammal science. - : Wiley. - 0824-0469 .- 1748-7692. ; 39:1, s. 251-273
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Journal article (peer-reviewed)abstract
- Body mass is a fundamental feature of animal physiology. Although sperm whales (Physeter macrocephalus) are the largest toothed predators on earth, body mass is seldom included in studies of their ecophysiology and bioenergetics due to the inherent difficulties of obtaining direct measurements. We used UAV-photogrammetry to estimate the weight of free-ranging sperm whales. Aerial photographs (23 calves, 11 juveniles, 55 nonmother adults, 13 mothers) were collected in the Eastern Caribbean and Mediterranean Sea during 2017–2020. Body length, widths, and heights (dorso-ventral distance at 5% increments) were measured from dorsal and lateral photographs, while body volume was calculated using an elliptical model. Volume varied noticeably (12.01 ± 4.79 m3) in larger animals (>8 m), indicating fluctuations in body condition of adults and mothers. Volume was converted to mass, using tissue-density estimates from catch data, animal-borne tags, and body-tissue composition. Average total body density ranged from 834 to 1,003 kg/m3, while the weight predictions matched with existing measurements and weight-length relationships. Our body-mass models can be used to study sperm whale bioenergetics, including inter- and intraseasonal variations in body condition, somatic growth, metabolic rates, and cost of reproduction.
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| 2. |
- Glarou, Maria, et al.
(author)
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Using Artificial-Reef Knowledge to Enhance the Ecological Function of Offshore Wind Turbine Foundations : Implications for Fish Abundance and Diversity
- 2020
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 8:5
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Research review (peer-reviewed)abstract
- 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.
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| 3. |
- Glarou, Maria, et al.
(author)
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Using off-the-shelf GPS loggers to assess co-occurrence between marine mammals and small-scale fisheries : a pilot study from the Mediterranean Sea
- 2022
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In: Journal of the Marine Biological Association of the United Kingdom. - : Cambridge University Press. - 0025-3154 .- 1469-7769. ; 102:5, s. 322-332
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Journal article (peer-reviewed)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.
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