Angel sharks (Squatinidae): A review of biological knowledge and exploitation

Abstract

Angel sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshoreoffshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of angel shark populations with fisheries and other human activities. Their dorso-ventrally flattened body shape, large size (most species attain >100 cm total length, L T) and demersal nature means that they may be taken in a variety of demersal fishing gears from birth. Available data indicate that angel sharks typically have a biennial reproductive cycle, with litter sizes generally <20 and the young born at c. 20-30 cm. The biological characteristics of angel sharks render them susceptible to overexploitation, as exemplified by the decline of Squatina squatina from many parts of its former range in the northeast Atlantic and Mediterranean Sea. Currently, half of the 22 recognized extant species of angel shark are classed as Threatened on the International Union for Conservation of Nature (IUCN) Red List (with a further three classified as Data Deficient). Given the biological vulnerability of angel sharks, and that many species are data-limited, the current paper provides a review of available biological information and fisheries data pertaining to this family.

The First Assessment on Metal Contamination in the Critically Endangered Sawback Angelshark (Squatina Aculeata) From North-Eastern Mediterranean

“…Angel sharks often occupy coastal waters and thus exposed to different contaminants, the high trophic level of this environment could increase the accumulation of such pollutants (Ellis et al, 2020). Therefore, the use of shark species as bio indicators has been underlined by numerous investigators for environmental monitoring studies (Adel et al 2018;Lozano-Bilbao et al 2018;Kim et al 2019).…”

“…The concentrations of Hg are not found at levels that would exceed most current guidelines for seafood products in the former studies on the other angelshark species, S. californica and S. squatina (Morris et al 1989;Escobar-Sánchez et al 2016). Ellis et al (2020) reported that there is no report on the contaminants that have impacted on angel sharks, and further studies are required on the potential impacts of habitat degradation and water quality for inhabiting areas of angel shark, especially industrialized areas. Therefore, the present nding with exceeded legalized limit of Hg concentrations are very valuable for the conservation and sustainability of S. aculeata as management consideration.…”

“…Ellis et al (2020) reported that few published studies on organic and inorganic(metals) contaminants in different Squatina species have been available. The high concentrations of mercury (Hg, 0.24 ± 0.27µg g -1 ) in the muscle of S. californica from the Gulf of Mexico was reported by Escobar-Sánchez et al (2016).…”

Species Delimitation of Southeast Pacific Angel Sharks (Squatina spp.) Reveals Hidden Diversity through DNA Barcoding

“…Thus, the detailed distribution of both species along the EPO remains uncertain, especially in the areas of North of South America where both species have been reported [14,15,18,44]. Additionally, angel sharks are target species and are captured by small-scale fisheries [28]. However, reports of landings are rather general and likely include several species of angel sharks, thus molecular tools could serve well for the accurate identification of the species landed, their distributions, and the fisheries with which they interact [28].…”

“…Additionally, angel sharks are target species and are captured by small-scale fisheries [28]. However, reports of landings are rather general and likely include several species of angel sharks, thus molecular tools could serve well for the accurate identification of the species landed, their distributions, and the fisheries with which they interact [28].…”