Sexual development and maturity scale for the angel shark Squatina squatina (Elasmobranchii: Squatinidae), with comments on the adequacy of general maturity scales

Osaer, Filip; Narváez, Krupskaya; Pajuelo, José G.; Lorenzo, José M.

doi:10.3354/sedao00012

Cited by 14 publications

(13 citation statements)

References 31 publications

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“…The estimated TL of the largest individual was a 200 cm female. Maturity data for angelsharks (Osaer, Narváez, Pajuelo, & Lorenzo, ) suggests that 53% of encountered sharks had not yet reached sexual maturity, while 47% were considered to be sexually mature. Two females were observed giving birth in June, while 12 gravid females were registered (three in February, two in March, five in June/July and two in December), some with mating scars.…”

Section: Resultsmentioning

confidence: 99%

Population structure, distribution and habitat use of the Critically Endangered Angelshark, Squatina squatina, in the Canary Islands

Meyers

Tuya

Barker

et al. 2017

Aquatic Conservation

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Angel sharks are among the most threatened fish worldwide, facing regional and global extinction. In Europe, populations of the three Critically Endangered angel sharks (Squatina aculeata, Squatina oculata and Squatina squatina) have been severely depleted. Taking advantage of the last global ‘hotspot’ of the angelshark, Squatina squatina, this study gathered data through a citizen science programme to describe the occurrence of this shark in the coastal waters of the Canary Islands. Specifically, this study described (1) the population structure, and (2) habitat use of this species, which was used in a Species Distribution Model to (3) examine realized and potential distribution patterns, and to (4) determine the relative importance of environmental predictors on the occurrence of S. squatina. Over the 12 months sampling period (April 2014 – March 2015), 678 sightings were reported. Individuals ranged from 20 to 200 cm (total length). Larger sightings of both females and neonates occurred mostly in April to July, i.e. during the pupping season. Males were significantly more frequent in November to January, i.e. during the mating season. Angelsharks were encountered at depths from <1 m to a maximum of 45 m. Small‐sized individuals (i.e. neonates) exclusively occurred in shallow water (0–25 m). Most sharks occurred on sandy bottoms adjacent to reefs. Even though sightings were recorded at all seven islands in the archipelago, there were fewer encounters in the western than the eastern islands. The Species Distribution Model indicated that the probability of occurrence mainly correlated with sea surface temperature, chlorophyll, salinity and depth. Areas with the greatest habitat suitability were in shallow water. The angelshark displayed spatial (vertical and horizontal) and temporal segregation by size and sex. This information is vital to inform conservation of this Critically Endangered shark in its last stronghold.

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Section: Resultsmentioning

confidence: 99%

Population structure, distribution and habitat use of the Critically Endangered Angelshark, Squatina squatina, in the Canary Islands

Meyers

Tuya

Barker

et al. 2017

Aquatic Conservation

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“…Collected B. torpedinis were measured in TL and identified based on Mann (1962) and Sawyer et al (1975). The maturity phase of S. squatina was assigned based on Osaer et al (2015).…”

Section: Methodsmentioning

confidence: 99%

The marine leech Branchellion torpedinis parasitic on the angelshark Squatina squatina and the marbled electric ray Torpedo marmorata

Narváez

Osaer

2016

Mar Biodiv

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The marine leech Branchellion torpedinis is parasitic on teleost and elasmobranch species. Reports along its wide distribution range include the Carribean Sea, the Mediterranean Sea, and the west and east coasts of the North Atlantic Ocean. Most of these records are isolated cases and limited just to the mention of the relationship. In this sense, the present communication is a novel report and a reliable, longterm, host-parasite record for the marine leech B. torpedinis based on observations in its natural habitat, and an expansion of the known distribution of this helminth to include the Canary Islands. The leech was observed attached to the dorsum of the angelshark Squatina squatina and of the marbled electric ray Torpedo marmorata during a scuba diving census. No noteworthy aspects were registered in the attachment area, the behavior or apparent fitness of the hosts. These findings are important because it provides useful information about the dispersal patterns of a rare marine leech and its relationship with the hosts, and gives the first insights into a parasite for T. marmorata in the Canary Islands.

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“…To partition juveniles (small-sized, recently-born, individuals with no operational reproductive system) from subadults and adults, we considered the maturity development information provided by: Capapé et al (2008) for M. aquila, Ismen (2003) for D. pastinaca, Capapé et al (1992) for G. altavela, Osaer et al (2015) for S. squatina, and Trindade-Santos and Freire (2015) for S. zygaena. Despite the fact that no information was available for T. grabatus, we considered that a size < 40 cm would correspond to juveniles, considering the maturity states of rays of the family Dasyateidae.…”

Section: Speciesmentioning

confidence: 99%

“Urbanite” rays and sharks: Presence, habitat use and population structure in an urban semi-enclosed lagoon

Tuya

Asensio²,

Navarro³

2020

Regional Studies in Marine Science

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There is a vital necessity to provide more biological data on rays and sharks to promote efficient conservation. In this study, we assembled a database of weekly sightings to describe temporal (seasonal) patterns in the presence of elasmobranchs within an urban, semi-enclosed, landscape (Las Canteras beach, Gran Canaria Island, eastern Atlantic). Data also provided insight into their habitat use and population structure. From October 2015 to October 2018, eight species, either endangered or ''data deficient'' according to the IUCN red list, were reported, including: the common eagle ray, Myliobatis aquila, the common stingray, Dasyatis pastinaca, the round stingray, Taeniurops grabatus, the spiny butterfly ray, Gymnura altavela, the bull ray, Aetomylaeus bovinus, the angel shark, Squatina squatina, the marbled electric ray, Torpedo marmorata and the hammerhead shark, Sphyrna zygaena. All species were predominantly observed at night. The species varied in their habitat use; D. pastinaca, G. altavela and S. squatina dominated in sandy and mixed bottoms, while M. aquila and T. grabatus were mostly found in rocky and mixed bottoms. Both D. pastinaca and T. grabatus did not show any seasonal pattern, with consistent records all year around. In contrast, M. aquila, G. altavela and S. squatina showed some degree of seasonality. For five species, small-sized individuals were observed. If semi-enclosed embayments at oceanic islands, under intense human presence, are used by juveniles of endangered rays and sharks, proper management, e.g. limitation of putative human interactions, need to be considered to avoid disturbances.

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Sexual development and maturity scale for the angel shark Squatina squatina (Elasmobranchii: Squatinidae), with comments on the adequacy of general maturity scales

Cited by 14 publications

References 31 publications

Population structure, distribution and habitat use of the Critically Endangered Angelshark, Squatina squatina, in the Canary Islands

Population structure, distribution and habitat use of the Critically Endangered Angelshark, Squatina squatina, in the Canary Islands

The marine leech Branchellion torpedinis parasitic on the angelshark Squatina squatina and the marbled electric ray Torpedo marmorata

“Urbanite” rays and sharks: Presence, habitat use and population structure in an urban semi-enclosed lagoon

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