Distribution and Abundance of Coastal Elasmobranchs in Tenerife (Canary Islands, NE Atlantic Ocean) with Emphasis on the Bull Ray, Aetomylaeus bovinus

Moreno, Jorge; Solleliet-Ferreira, S.; Riera, Rodrigo

doi:10.1007/s41208-021-00316-1

Cited by 2 publications

(2 citation statements)

References 22 publications

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“…Regarding such data limitations and needs, the Scientific, Technical, and Economic Committee for Fisheries (2017) [3,21] has noted that the current data requirements and sampling efforts of the EU fisheries data collection programme on rays and skates cannot sufficiently provide robust estimates of various parameters (e.g., maturity, commercial catch composition, sex ratios, and indices of abundance) necessary for stock assessment and management. A case in point is the spiny butterfly ray, Gymnura altavela [22], a seasonally common ray in the shallow waters of the Canary Islands [23,24] that has been classified as critically endangered in the Mediterranean and Europe as well as endangered worldwide [25][26][27]. Nevertheless, the lack of data from other areas within the range of G. atlavela makes it difficult to define the conservation status of its population [27].…”

Section: Introductionmentioning

confidence: 99%

“…Within the Canary Islands in the Eastern Central Atlantic, the spiny butterfly ray is as common as other benthic elasmobranchs [24,35,36] and, at the population level, seems to have a much better conservation status than in other European waters, including the Mediterranean Sea [37]. Two possible explanations for the species' seemingly favourable conservation status in the Canary Island archipelago are that it is not targeted by local artisanal fisheries and that trawling activity has been banned in the archipelago since 1986.…”

Section: Introductionmentioning

confidence: 99%

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Aggregative Behaviour of Spiny Butterfly Rays (Gymnura altavela, Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic

Espino-Ruano

Castro

Guerra‐Marrero

et al. 2023

Animals

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The presence of spiny butterfly rays, Gymnura altavela, in waters less than 20 m deep off the Canary Islands shows marked seasonality, with relatively high abundances in the summer and autumn. Large aggregations of sometimes hundreds of individuals, primarily females, appear in specific shallow areas of the archipelago and seem to be associated with the seasonal variation in water temperature. This seasonal pattern of presence or absence in shallow areas suggests that spiny butterfly rays migrate into deeper waters or other unknown areas during the rest of the year. G. altavela shows sexual dimorphism; in our study, females were larger and more abundant than males, with a sex ratio of 1:18.9. The species’ estimated asymptotic length, L∞, was 183.75 cm and thus close to the common length reported for the species (200 cm). The von Bertalanffy growth constant (k) oscillated between 0.210 and 0.310 year−1, as similarly described for the species in the Western North Atlantic off the U.S. coast. From June to November, the seawater temperature oscillated between 19 and 24 °C, and massive aggregations of females occurred at 22–24 °C and in a few specific sandy beaches on the islands. Spiny butterfly rays, mostly females, show a preference for aggregating in shallow waters during summertime, probably conditionate to mating or breeding behaviour.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aggregative Behaviour of Spiny Butterfly Rays (Gymnura altavela, Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic

Espino-Ruano

Castro

Guerra‐Marrero

et al. 2023

Animals

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Novel use of deep neural networks on photographic identification of epaulette sharks (Hemiscyllium ocellatum) across life stages

Lonati,

Jahanbakht,

Atkins

et al. 2024

Journal of Fish Biology

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Photographic identification (photo ID) is an established method that is used to count animals and track individuals' movements. This method performs well with some species of elasmobranchs (i.e., sharks, skates, and rays) where individuals have distinctive skin patterns. However, the unique skin patterns used for ID must be stable through time to allow re‐identification of individuals in future sampling events. More recently, artificial intelligence (AI) models have substantially decreased the labor‐intensive process of matching photos in extensive photo ID libraries and increased the reliability of photo ID. Here, photo ID and AI are used for the first time to identify epaulette sharks (Hemiscyllium ocellatum) at different life stages for approximately 2 years. An AI model was developed to assess and compare the reliability of human‐classified ID patterns in juvenile and neonate sharks. The model also tested the persistence of unique patterns in adult sharks. Results indicate that immature life stages are unreliable for pattern identification, using both human and AI approaches, due to the plasticity of these subadult growth forms. Mature sharks maintain their patterns through time and can be identified by AI models with approximately 86% accuracy. The approach outlined in this study has the potential of validating the stability of ID patterns through time; however, testing on wild populations and long‐term datasets is needed. This study's novel deep neural network development strategy offers a streamlined and accessible framework for generating a reliable model from a small data set, without requiring high‐performance computing. Since many photo ID studies commence with limited datasets and resources, this AI model presents practical solutions to such constraints. Overall, this approach has the potential to address challenges associated with long‐term photo ID data sets and the application of AI for shark identification.

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Distribution and Abundance of Coastal Elasmobranchs in Tenerife (Canary Islands, NE Atlantic Ocean) with Emphasis on the Bull Ray, Aetomylaeus bovinus

Cited by 2 publications

References 22 publications

Aggregative Behaviour of Spiny Butterfly Rays (Gymnura altavela, Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic

Aggregative Behaviour of Spiny Butterfly Rays (Gymnura altavela, Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic

Novel use of deep neural networks on photographic identification of epaulette sharks (Hemiscyllium ocellatum) across life stages

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