Marine wildlife stranding is a global phenomenon that affects both invertebrates and vertebrates (Chan et al., 2017;Cockcroft, 2001). Many definitions are available, being guided mostly by the taxonomic group affected. The National Oceanic and Atmospheric Administration (NOAA) recognizes three main taxonomical categories of strandings: cetaceans, pinnipeds and sea turtles. Stranded animals may be found dead (either on land or floating) or alive but unable to return to sea due to injury or illness. Broader definitions are also available and do not consider taxonomic groups, but simply the presence of an aquatic animal on land, whether dead or alive (but physiologically/physically unable to return to the sea) (
Sharks and rays are among the most threatened vertebrates, mostly due to commercial fisheries. Data on incidental capture is sparse, but it is estimated that about 50% of reported global catches of elasmobranchs are from bycatch. Elasmobranchs are captured in a variety of fishing gear throughout the world. One promising strategy to minimize incidental catches is the release of live sharks and rays. However, so far, no critical analysis had been carried out to assess the importance of release as a measure to mitigate the impacts of bycatch. Results indicated that despite onboard releases being cited in Plans of Action (along ZEEs) and recommendations/regulations of Regional Fisheries Management Commissions (in international waters), this measure is treated as secondary and has voluntary adherence, which can significantly reduce its efficiency. Moreover, among the Best Fishing Practice Manuals currently available, although release is cited as a priority, most of them do not consider the dynamics of the location/fishing modality for which it was developed. A change on how release is perceived is needed to prioritize this conservation strategy, as well as its potential as a social tool to reduce the impacts of bycatch on sharks and rays.
In Brazil, regulations for fishing for elasmobranchs are scarce, as well as insufficient monitoring and management. The first catch regulation for the group was published in 1998 (IBAMA No. 121/98). Despite the ban on finning, the legislation provides legal support for evisceration and decapitation prior to landing. Such practices have become particularly problematic for proper monitoring since decharacterization impairs the correct identification of species. In addition, processing is detrimental to research, as many studies rely on sampling of biological material (e.g., blood), posing an additional challenge for researchers using commercial fishing animals for scientific purposes. This study aimed to characterize the frequency of this practice in a representative artisanal fishing community in the fishing of elasmobranchs. The three years of monitoring show that landing patterns of gutted and beheaded animals are influenced by the species caught and the catch volumes of the day. In addition, endangered species protected by legislation were mostly landed already processed. We discuss the findings focusing on the need to revise the legal framework for the commercial landing of elasmobranchs and possible promising ways to address this challenge.
Elasmobranchs have a very distinct metabolism, and many aspects related to the energetic dynamics of these animals remain poorly investigated. The reproductive period is particularly vulnerable for viviparous species, as part of the energy reserves of the parental biomass is reallocated for gamete production and embryo development. In this context, this study aimed to characterize parental metabolite provisioning to the offspring (both sperm and developing embryos) of the Brazilian Guitarfish, Pseudobatos horkelii, through glucose, β-hydroxybutyrate, triglycerides, and total cholesterol determinations in the uterine liquid (UL) and serum of pregnant females and in the seminal fluid (SF) and serum of males during the copulation period. No significant difference was observed for the analyzed markers between the UL and SF. Except for triglycerides, higher in female serum samples, all other energy markers were present at similar concentrations in the serum of both females and males. When comparing female UL and serum, significant differences were observed for triglycerides and total cholesterol. No differences were observed between SF and serum in males. The results indicate that all markers are being made available to offspring, possibly complementary to the yolk in the case of maternal liquid, and as an additional source for sperm mobilization required during egg fertilization in the case of the paternal fluid. Correlations between the markers in the parental matrices were also noted, compatible with the metabolic pathways activated during energy mobilization in vertebrates. Moreover, distinct marker predominance patterns were also noted for both UL and SF. Energy mobilization characterization directed to offspring through parental fluids aids in unraveling metabolic dynamics during the reproduction stage while also providing support for stress physiology studies to evaluate the indirect effects of parental allostatic overload in both sperm and developing embryos. Finally, energy mobilization assessments of parental fluids may also help elucidate how internal fertilization and viviparity evolved in this very distinct taxonomic group.
Capture and handling can have sublethal consequences on elasmobranchs, even when individuals are quickly released to comply with legislation or fishermen's ethics on voluntary conservation. Dystocia is characterized by the physical inability to deliver the neonate, even when it is ready for birth. So far, this phenomenon has been reported only in Cownose rays kept under human care. The present study aimed to report the occurrence of dystocia in a free-living Cownose ray (Rhinoptera bonasus), possibly caused by capture stress. Allied to other sublethal effects, dystocia can compromise population recruitment and increase post-capture mortality, especially for older females. Still, considering that this phenomenon was observed and described only in captivity, reports of occurrence in the wild are essential to increase knowledge on the topic and adapt protocols used in captivity for free-ranging animals, as a way to reduce the negative impacts of dystocia.
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