Assessment of the conservation status of Chondrichthyans: underestimation of the pollution threat

Abstract

Cartilaginous fish include sharks, rays, skates, sawfish, and chimaeras. Their habitat ranges from shallow coastal waters to deep ocean floors, estuarine areas as well as rivers and inland waters. Overfishing is considered to be the main threat to their existence, but there are many more stressors that these species face. Pollution is an issue that concerns aquatic organisms at every level, and Chondrichthyans are no exception. Here, we looked at their IUCN Red List assessment, and noticed a lack of information regarding anthropogenic contamination for these species. Out of 1124 cartilaginous fish species assessed, only 17 Selachimorpha and 32 Batoidea species were considered to be facing a "pollution threat"; in most cases, the threat was assigned not from direct ecotoxicological studies of the specimens, but because the species inhabited areas likely to be contaminated. An update on the conservation status of these species is urgently needed. Further, there is a fundamental need to study the effects of contaminants on Chondrichthyans as they play a key role in aquatic ecosystems.

Holoprosencephaly and other morphological abnormalities in the silky shark Carcharhinus falciformis

“…Records in the area may be related to negative effects of high concentrations of pollutants recorded in some parts of the Gulf of California, although this type of analysis has not been carried out on the specimens analysed so far (Escobar-Sánchez et al, 2013;Consales and Marsili, 2021). Caution must be recommended when assigning a clear cause of elasmobranch deformities from a single specimen, especially when additional foetuses in the mother show normal anatomical structure, as in this case.…”

New Occurrences of the Tiger Shark (Galeocerdo cuvier) (Carcharhinidae) off the Coast of Rio de Janeiro, Southeastern Brazil: Seasonality Indications

“…Furthermore, tiger sharks exhibited a lower reproductive output than expected from the literature for specimens captured along the coast of Hawai’i [ 62 ], making juvenile survival and the protection of nursery, feeding, and growing areas potentially critical for conservation strategies, even more so as chemical contamination is of significant concern in juvenile stages [ 63 ]. It is also important to note that although pollution has recently been identified as a priority for conservation efforts, especially for elasmobranchs [ 64 , 65 ], data are still scarce for many species, posing a significant knowledge gap for elasmobranch conservation. Additionally, a database such as the one produced herein is the first step toward the design of new research on a species that, although not yet categorized as threatened, is considered key to food web maintenance.…”

Stable isotopes provide evidence of a trophic shift in the lesser spotted dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea

“…The present study can be used as a complementary baseline for future interdisciplinary research. In the light of diverse anthropogenic and climate change scenarios (Serena et al, 2015;Consales & Marsili, 2021), vertebrae is a feasible biological matrix to study present and previous conditions registered during the lifetime of an organism (Bevacqua et al, 2021).…”

“…It can be found from the intertidal zone to the continental slope, with highest abundances reported at depths of 200-500 m (Olaso et al, 2005;Kousteni & Megalofonou, 2019;Leonetti et al, 2020). Considering that S. canicula is one of the most abundant demersal sharks in the Mediterranean Sea, and the one most resilient to the impact of human activities, the understanding of its ecology is fundamental to strengthen fishing management and conservation regulations in European countries such as Portugal, Spain, Greece, and Italy (Finotto et al, 2015;Serena et al, 2015;Ebert & Dando, 2021;Consales & Marsili, 2021).…”