Assessment of the physiological vulnerability of the endemic and critically endangered Daggernose Shark: A comparative approach to other Carcharhiniformes

Abstract

IntroductionThe current Isogomphodon oxyrhynchus (Daggernose Shark) population status Q7points to 99% losses in the last decade due to certain biological traits, site fidelity, and historical high representativeness as bycatch in artisanal fisheries. This species is listed as Critically Endangered (CR), both in the IUCN and the Brazilian Red Lists. Its vulnerability is so high that its recovery potential requires protection from ongoing fishing pressure.ObjectiveIn this context, this study aimed to evaluate the health status of Daggernose sharks and their ability to cope with allostatic overload in a comparative analysis with other Carcharhinid and Sphyrnid sharks.MethodsSharks incidentally caught by the artisanal fleet in the state of Maranhão, on the Brazilian Amazon Coast, were sampled for blood, and serum was used to assess biochemical markers.ResultsThe findings indicate significant differences in Daggernose Shark homeostatic capacity for ALP, ALT/GTP, creatinine, lactate, urea, total cholesterol, and triglycerides, pointing to lower health scores and recovery capacity when compared to other Carcharhiniformes inhabiting the same region.Discussion and conclusionsIt is possible that such vulnerability is a result of fisheries-induced evolution, leading to remaining populations with very low chances of fully recovering. Conservation planning is thus urgent, as current legislation based on fishing bans does very little for the species. International collaboration and longterm recovery measures are necessary, including the creation of MPAs specially designed for the species and captive maintenance aiming to monitor health status and carry out breeding attempts.

Rocket launches threaten global conservation

“…M is among the world's richest storehouses of biological and genetic diversity, supporting 90% of marine organisms during part of their lifecycle and are crucial for 80% of global sh catches 31 . Since the damages of launch accidents and falling debris on marine biodiversity have been attended 32,33 , further reducing potential threats to biodiversity priority biome like M, by strengthening ecological assessments and monitoring, is crucial if conservation efforts are to secure their biodiversity.…”

“…Importantly, coastal and marine RLS have a greater conservation impact than inland sites, with over 70% overlapping with PA, which suggests that coastal and marine launches require heightened attention. For example, the Brazilian space program has adversely affected coastal shark populations, with signi cantly elevated levels of rubidium found in apex predatory sharks near the Alcântara Space Center 33 . Furthermore, rocket launch debris threatens marine life within PA: smaller fragments can cause injury or mortality through ingestion, while larger pieces disrupt seabed ecosystems by providing unnatural substrates for benthic invertebrates, altering community structures 32 .…”

Evolutionary History and Taxonomic Reclassification of the Critically Endangered Daggernose Shark, a Species Endemic to the Western Atlantic

“…However, landing shark and ray catches with the fins still attached to the body only became mandatory in 2012 [96,97]. Furthermore, the ability of C. oxyrhynchus to recover health after stressful interactions may result in greater survival risks compared to other Carcharhiniformes even if released alive after accidental capture [98].…”

Unveiling the Threats Beneath: Fish Mislabeling in the Brazilian Amazon Coast and its Impacts on the Critically Endangered Daggernose Shark

“…The Daggernose Shark is an endemic species facing one of the highest risks of extinction and exhibiting low resilience scores, rendering it extremely vulnerable to fishing pressure (Lessa et al 2016). This scenario is exacerbated by its low genetic diversity (Rodrigues‐Filho et al 2009) and high physiological vulnerability (Wosnick et al 2023). The landing and trade of this species is strictly prohibited in Brazil, as aquatic organisms classified as threatened (vulnerable, endangered, or critically endangered) cannot be retained, even if incidentally caught or brought on board dead (Ordinance 445, Brazil's Ministry of Environment/2014).…”