Fishing profile and commercial landings of shark and batoids in a global elasmobranchs conservation hotspot.

This paper describes the fishing profile and the temporal variation in the commercial landings of elasmobranchs in a global hotspot for their conservation and investigates the variables that influenced the landings. Census data on commercial catches were obtained between April 2008 and October 2010 from nine landing sites in Bragança (Pará, northern Brazil). Five vessel types, four fishing gears, and eight fishing techniques engaged with elasmobranch capture were identified. A total of 2,357 landings were recorded, with a total production of 354 t. The highest yields were recorded in 2009, with sharks being harvested mostly by small and medium-sized vessels, and batoids, by small vessels and canoes. Drifting nets and longlines played a prominent role in elasmobranch fisheries. The results show that the landings were influenced by days at sea, which is common in tropical fisheries. The elasmobranch data series is discontinuous as statistics are absent for most fishing sites albeit imperative for proper management, as well as relevant for decision-makers focusing on their conservation.

Expanding records of occurrence of the whale shark (Rhincodon typus) in The Bahamas and a call for sustainable tourism practices.

This report updates our understanding of whale shark occurrences in The Bahamas by drawing upon a variety of data sources. Our findings reveal previously unreported sighting locations, often associated with tourism activities, underscoring the pivotal role played by nontraditional data sources in addressing knowledge gaps. These revelations emphasize the ongoing necessity for monitoring efforts. Additionally, we have found cases that raise concerns related to unregulated human-shark interactions in the region, highlighting the pressing need for sustainable tourism practices within Bahamian waters.

Photobacterium damselae subspecies damselae Pneumonia in Dead, Stranded Bottlenose Dolphin, Eastern Mediterranean Sea.

Photobacterium damselae subspecies damselae, an abundant, generalist marine pathogen, has been reported in various cetaceans worldwide. We report a bottlenose dolphin in the eastern Mediterranean Sea that was found stranded and dead. The dolphin had a severe case of chronic suppurative pneumonia and splenic lymphoid depletion caused by this pathogen.

Carbonic anhydrase in elasmobranchs and current climate change scenario implications.

The enzyme carbonic anhydrase (CA) has well-known functions in acid-base balance, respiratory gas exchange, and osmoregulation in teleost fishes. However, studies concerning the role of CA in elasmobranchs are still scarce. Therefore, the aim of this study is to present the current status of CA studies in sharks and rays, as well as to identify gaps and emerging needs, in order to guide future studies. This review is organized according to the main roles of CA, with further considerations on climate change and CA effects indicated as paramount, as strategies in the face of climate change can be crucial for species response. The literature review revealed a reduction in publications on CA over the years. In addition, a historical research differentiation is noted, where the first assessments on the subject addressed investigations on basic CA functions, while the most recent studies present a comparative approach among species as well as interdisciplinary discussions, such as ecology and phylogeny. Considering that several elasmobranchs are threatened, future studies should prioritize non-lethal methodologies, in addition to expanding studies to climate change effects on CA.

Evaluating conservation status and governmental efforts towards regional flagship species in Brazil.

Several strategies have been adopted to optimize biodiversity conservation. The use of fauna and flora species as flagships can help increase public commitment and raise funds for their conservation. However, species choices must be well balanced, considering not only intrinsic aspects (e.g., risk of extinction and ecological role), but also social, cultural, and economic aspects of the region where the flagship will be adopted. Brazil is one of the countries with the greatest diversity on the planet. Nevertheless, there are several challenges associated with natural resources conservation. Flagships have been adopted informally for decades throughout the country but there are no efforts to evaluate these strategies results for the preservation of the selected species. The aim of this study was to carry out an extensive survey on regional flagship species, their conservation status, level of endemism, and domestic legislation currently in force for their protection or human use. A total of 62 flagships were identified, with at least one species of flora and one of fauna for each of the 27 Brazilian Federative Units. The animals most commonly used as regional symbols are birds, followed by mammals. Flora species used as regional symbols are quite diverse. However, they are all somehow used by humans. As for legal protection, there are government measures for endangered species. Nevertheless, most species used as regional symbols are not at risk of extinction and, for this reason, do not receive any legal protection. Moreover, while some flagships are endemic, others are alien species, indicating that this criterion is not considered when choosing regional symbols. In the overall analysis it was noted that species choice could be optimized to highlight the national biodiversity. Despite efforts to establish legal measures for their preservation, few effective results have been observed. Therefore, improved effective measures for their conservation should be adopted to guarantee the effectiveness of flagship species for biodiversity conservation.

Benzocaine-induced stress in the euryhaline teleost, Centropomus parallelus and its implications for anesthesia protocols.

The use of anesthetic in fish farming is a traditional practice which aims to reduce the stress caused by transport and handling. However, anesthesia-induction protocols are commonly established and implemented without proper physiological/behavioral evaluation. Additionally, concentration and time of exposure to the anesthetic are often set without considering species-specific responses. The fat snook (Centropomus parallelus) is a fish with great potential for aquaculture. Given its remarkable euryhalinity, it can grow in fresh- or seawater. Most studies on fat snook anesthesia tested natural compounds (essential oils) instead of traditional anesthetics. However, the use of benzocaine is much more common in the commercial sector, as it is easy to obtain and of relatively low cost. The present study aimed at analyzing the effects benzocaine exposure on glucose and cortisol plasma levels (two traditional stress markers in teleost fish), as well as on plasma osmolality, chloride and magnesium, (indicators of osmo-ionic allostasis) in animals acclimated to different salinities. Results showed that while osmo-ionic allostasis was strictly maintained across the treatments, time of anesthesia had a strong positive relationship to plasma cortisol and glucose, regardless the salinity of exposure and acclimation. The results are discussed as they relate to anesthesia protocols and how stress response generated by time of anesthesia may challenge farming flexibility.

Microscopic aspects of electrosensory system on the partially euryhaline lesser guitarfish.

The electrosensory system on elasmobranchs consists of subcutaneous electroreceptor organs known as ampullae of Lorenzini. The present study investigated the ampullae of Lorenzini morphology of the lesser guitarfish Zapteryx brevirostris, using light microscopy and scanning electron microscopy. The pore number found in the ventral skin surface is much higher than that found in the dorsal portion, characteristic of species that inhabit the euphotic zone. Under light microscopy it was possible to observe that the wall canal consists of a single layer of squamous epithelial cells. The canal features distal expansion, where the ampullae are located with up to six alveoli. The sensory epithelium of ampullae is composed by cubic cells, with oval nucleus, restricted to the interior of the alveoli. With analysis the clusters under scanning electron microscopy, it was possible to observe the structure and the random arrangement of individual ampullae, canals and nerves. The distribution of dorsal and ventral pores and ampullae in Z. brevirostris resembled those of the same family. The number of alveoli per ampullae was similar to that found in euryhaline elasmobranchs species, suggesting that the morphological organization in Z. brevirostris is linked to its possible evolutionary transitory position among batoids.

Ultrasonography as a promising methodology to indicate captured-induced abortion in viviparous elasmobranchs.

This study aimed to characterize morphological aspects related to abortion through a non-lethal approach in the shortnose guitarfish Zapteryx brevirostris, an endemic and threatened species commonly caught by artisanal fisheries. Two females with signs of abortion and one female exhibiting external signs of pregnancy were purchased alive at a fish market during the period when this species has developing embryos in southern Brazil. Scans were conducted using a portable ultrasound. Females with signs of abortion revealed an absence of embryos despite having a similar morphology of the uterus when compared to the pregnant female. Examination of the pregnant female revealed the presence of two embryos, measuring c. 100 mm, each detected through their midline. This study presents new data on uterine macromorphology following successive abortive events in a viviparous elasmobranch species and validates ultrasonography as a diagnostic tool for the species. Ultrasonography is an effective, non-lethal and less-invasive methodology that is recommended for use in future studies of abortion and other reproductive events in elasmobranchs.

A preliminary investigation into the morphology of oral papillae and denticles of blue sharks (Prionace glauca) with inferences about its functional significance across life stages.

Sensory organs in elasmobranchs (sharks, skates, rays) detect and respond to a different set of biotic and/or abiotic stimuli, through sight, smell, taste, hearing, mechanoreception and electroreception. Although gustation is crucial for survival and essential for growth, mobility, and maintenance of neural activity and the proper functioning of the immune system, comparatively little is known about this sensory system in elasmobranchs. Here we present a preliminary investigation into the structural and dimensional characteristics of the oral papillae and denticles found in the oropharyngeal cavity of the blue shark (Prionace glauca) during embryonic development through adulthood. Samples were obtained from the dorsal and ventral surface of the oropharyngeal cavity collected from embryos at different development stages as well as from adults. Our results suggest that development of papillae occurs early in ontogeny, before the formation of the oral denticles. The diameter of oral papillae gradually increases during development, starting from 25 µm in stage I embryos, to 110 µm in stage IV embryos and 272-300 µm in adults. Embryos exhibit papillae at early developmental stages, suggesting that these structures may be important during early in life. The highest density of papillae was observed in the maxillary and mandibular valve regions, possibly related to the ability to identify, capture and process prey. The oral denticles were observed only in the final embryonic stage as well as in adults. Accordingly, we suggest that oral denticles likely aid in ram ventilation (through reducing the hydrodynamic drag), to protect papillae from injury during prey consumption and assist in the retention and consumption of prey (through adhesion), since these processes are only necessary after birth.

Talking to the dead: using Post-mortem data in the assessment of stress in tiger sharks (Galeocerdo cuvier) (Péron and Lesueur, 1822).

Sharks are very sensitive to stress and prone to a high mortality rate after capture. Since approximately 50 million of sharks are caught as bycatch every year, and current recommendations to reduce the impact of commercial fishing strongly support immediate release, it is imperative to better understand post-release mortality caused by the stress of capture and handling. Blood samples allow the assessment of stress levels which are valuable tools to reduce mortality in commercial, recreational and scientific fishing, being essential for the improvement in those conservation measures. Biochemical analyses are widely used for sharks as stress indicators, with secondary plasma parameters (lactate, glucose and ions) being the most often employed assays. However, it is virtually impossible to determine baseline plasma parameters in free-ranging sharks, since blood withdrawal involves animal capture and restrain, which are stressful procedures. This study aims at analyzing secondary parameters of five healthy tiger sharks captured with circular hooks and handlines in Fernando de Noronha (Northeastern Brazil) and comparing them with secondary parameters of three dead tiger sharks caught off Recife (also Northeastern Brazil). The results showed that the analysis of some plasma constituents in dead animals may be an efficient tool to assess stress and lethality. However, traditional parameters such as glucose and calcium, need to be used with caution. The results also demonstrated the extreme importance of urea and phosphorus for assessing stress response and mortality in tiger sharks, both parameters frequently neglected and of utmost importance for shark's homeostasis.

From screens to seas: tech contaminants in tiger sharks.

The potential negative impacts of Technology-Critical Elements (TCEs) on the environment and wildlife, despite increasingly recognized, remain largely overlooked. In this sense, this study aimed to investigate the concentrations of several TCEs, including rubidium (Rb), titanium (Ti) and various Rare Earth Elements (REEs), in different tissues of tiger sharks. Sharks incidentally caught by artisanal fleets in southern Brazil were opportunistically sampled and liver, gills, kidneys, heart, muscle, eyes, brain, skin, and teeth were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Significant Rb concentration variations were observed across different tissues, with higher levels detected in kidneys and lower levels in the liver. Titanium concentrations also exhibited significant differences, with higher levels detected in teeth and lower levels in liver. Although no statistical differences were observed for the analyzed REEs, a trend of higher accumulation in the liver, gills, and skin was noted. Light Rare Earth Elements (LREEs) were found predominantly in all organs, with neodymium, lanthanum, and cerium as the most significant REEs detected. Several statistically significant correlations were identified between Rb and REEs, as well as between Ti and REEs, indicating systemic transport of these elements across different tissues. These findings indicate that the growing extraction and disposal of metallic elements, driven by technological advancements, may lead to their assimilation by marine fauna, particularly at higher trophic levels. The potential harmful effects on these organisms remain unknown and require urgent investigation. Additionally, as mining activities intensify globally, precise legislative measures are essential to address environmental concerns, species conservation, and human health considerations.

"Cocaine Shark": First report on cocaine and benzoylecgonine detection in sharks.

Cocaine (COC) and benzoylecgonine (BE), the main COC metabolite, have been detected in aquatic ecosystems. Studies focusing on wild fish are, however, very limited, and no reports concerning elasmobranchs are available. This study investigated COC and BE levels in Brazilian Sharpnose sharks (Rhizoprionodon lalandii) (n = 13) using LC-MS/MS. All samples (13/13) tested positive for COC, with 92 % (12/13) testing positive for BE. COC concentrations (23.0 µg kg-1) were over 3-fold higher than BE (7.0 µg kg-1). COC levels were about three-fold significantly higher in muscle (33.8 ± 33.4 g kg-1) compared to liver (12.2 ± 14.2 µg kg-1). Females presented higher COC concentrations in muscle (40.2 ± 35.8 µg kg-1) compared to males (12.4 ± 5.9 µg kg-1). Several positive statistical correlations were noted between COC and BE (rho = 0.84) in females, indicating systemic COC transport and metabolization, as well as between BE and weight (rho = 0.62), and between COC and the Condition Factor (rho = 0.73). A strong correlation was noted between BE and COC in the muscle of non-pregnant females (rho = 1.00). This study represents the first COC and BE report in free-ranging sharks, and the findings point to the potential impacts of the presence of illicit drugs in environments.

Some euryhalinity may be more common than expected in marine elasmobranchs: the example of the South American skate Zapteryx brevirostris (Elasmobranchii, Rajiformes, Rhinobatidae).

Elasmobranchs are essentially marine, but ~15% of the species occur in brackish or freshwater. The Brazilian marine coastal skate Zapteryx brevirostris, non-reported in nearby estuaries, was submitted to 35, 25, 15, and 5 psu, for 6 or 12h (n=6). Plasma was assayed for osmolality, urea, and ions (Na(+), Cl(-), K(+), Mg(2+)). Muscle water content was determined, and the rectal gland, kidney and gills were removed for carbonic anhydrase (CA) and Na(+),K(+)-ATPase (NKA) activities. The skate survived to all treatments. Plasma osmolality and urea levels decreased respectively by 27% and 38% after 12h in 5 psu (with respect to levels when in seawater), but plasma Na(+), Cl(-), and Mg(2+) were well regulated. Plasma K(+) showed some conformation after 12h. Muscle hydration was maintained. Branchial CA and NKA did not respond to salinity. Rectal gland NKA decreased upon seawater dilution, while renal NKA increased. This skate was shown to be partially euryhaline. The analysis of plasma urea of elasmobranchs in brackish and freshwater versus salinity and time-allied to the widespread occurrence of some euryhalinity in the group-led us to revisit the hypothesis of a brackish water habitat for elasmobranch ancestors.

Almost nothing is known about the tiger shark in South Atlantic waters.

The tiger shark (Galeocerdo cuvier) has been relatively well assessed concerning biology and ecology aspects in both Atlantic and Pacific North America and in Caribbean waters. The amount of data in these regions has led to the species protection under capture quotas and with the creation of sanctuaries. The reality in developing countries, however, is the exact opposite, with scarce information on the species in the southern hemisphere, namely South American and African waters. In these regions, protection measures are insufficient, and studies on tiger shark biology and ecology are scarce, significantly hindering conservation and management efforts. Thus, the aim of this study was to compile scientific literature on the tiger shark in the South Atlantic and discuss the impact of these data (or lack thereof) distributed within a total of ten research categories for guiding management plans. In total, 41 scientific publications on different G. cuvier biology and ecology aspects were obtained. The most studied topics were Feeding Ecology (n = 12), followed by Human Interactions (n = 8), and Movements and Migration (n = 7). Northeastern Brazil (Southwest Atlantic) was the most researched area, probably due to the higher coastal abundance of tiger sharks in this area, alongside a high number of recorded attacks, justifying funding for studies in the region. No studies carried out in other South American or African countries were found. It is important to mention that even though some research topics are relatively well covered, a severe knowledge gap is noted for risk assessments and fisheries management, with a proposition for the implementation of sanctuaries noted. This is, however, particularly worrisome, as the South Atlantic is mostly unexplored in this regard for tiger sharks. It is also important to note how different the attention given to this species is in the North Atlantic when compared to the South region. Lastly, we highlight that the existence of sub-populations, the lack of migratory corridors geographically connecting distinct areas used by the species, and the lack of fisheries statistics on tiger shark landings, all increase the vulnerability of this species in the South Atlantic.

Ecotoxicology applied to conservation: Potential negative metal and metalloid contamination effects on the homeostatic balance of the critically endangered Brazilian guitarfish, Pseudobatos horkelii (Elasmobranchii: Rhinobatidae).

Metal contamination poses a significant threat to elasmobranchs, underscoring the need for targeted conservation approaches. The critically endangered Brazilian guitarfish, Pseudobatos horkelii, confronts an array of challenges, notably overexploitation, putting its survival at risk. Our study investigated the potential toxicity arising from arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) contamination across various adult guitarfish tissues from southeastern Brazil. Serological stress indicators, nutritional metabolites, and creatinine, an organ function marker, were also assessed, and Selenium (Se) levels were also investigated for possible protective effects. Our investigation unveiled significant correlations between metal concentrations and the determined physiological markers, shedding light on potential adverse effects. Remarkably, six correlations were indicative of how Hg and Pb negatively impact hepatic metabolite assimilation, while As was shown to influence renal phosphorus dynamics, Cd to affect rectal gland phosphorus regulation, and Pb to influence creatinine production in muscle tissue. Furthermore, Se demonstrated protective properties against Cd, Hg, and Pb, suggesting a role in alleviating the toxicity of these elements. Despite probable protective Se influences, the detected elemental interactions still suggest potential for organ impairment. These findings gain heightened significance within the context of the cumulative stressors faced by the Brazilian guitarfish, with metal contamination exhibiting the capacity to erode this species resilience against both anthropogenic and environmental pressures, thereby disrupting systemic equilibrium and jeopardizing wild populations. By investigating the intricate balance between metal accumulation and physiological consequences, our study contributes with crucial insights into potential conservation strategy formulations towards pollution for this critically endangered elasmobranch species.

First report on the serum chemistry and haematology of free-ranging dusky (Carcharhinus obscurus) and sandbar (Carcharhinus plumbeus) sharks in the eastern Mediterranean Sea.

Shark assessments in the Mediterranean Sea are still scarce, and serum chemistry and haematological data have yet to be reported for wild dusky (Carcharhinus obscurus) or sandbar (Carcharhinus plumbeus) shark populations in the Mediterranean Sea. Herein, blood samples were obtained from adult dusky (n = 23) and sandbar (n = 14) sharks from an aggregation site near the Hadera power and desalination plants in Israel in the winters of 2016-20. Several serum chemistry analytes were characterized with relation to stress, body size and environmental conditions. Glucose concentrations were higher, while total cholesterol concentrations were lower in dusky sharks than in sandbar sharks, potentially due to distinct metabolic pathways utilized during the capture-related activity by both species. However, differences in sex and size are noted and should be considered. The blood cell morphology of both species was consistent with previous findings for sandbar sharks. Atypical monocytes were noted in one dusky shark. Preliminary and exploratory reference intervals for female dusky sharks were calculated for glucose, triglycerides, total cholesterol, total protein and creatine kinase. These data must be viewed with caution due to the potential influence of capture-related stress on analyte concentrations and activities and the fact that only females were employed in the calculations. Moreover, the sampling site is adjacent to coastal power and desalination plants, which may significantly affect shark physiology. Although limited, this novel database on dusky and sandbar shark serum chemistry and haematology aspects is essential as a first attempt to obtain data on these species in the eastern Mediterranean Sea and for future conservation and long-term biomonitoring efforts.

First description of a Gammaherpesvirus in a common dolphin (Delphinus delphis) from the Eastern Mediterranean Sea.

In September 2020, a male common dolphin (Delphinus delphis) was found dead on a beach near Bat-Yam, Israel. A small, raised, well circumscribed penile lesion (i.e., mass) was identified and removed for histology and molecular characterizations. By histology, the penile mass presented focal keratinization of the squamous epithelium and a mild ballooning of acanthocytes in lower epithelium levels, as well as features compatible with viral plaques, and tested positive for a gammaherpesvirus through molecular characterization analyses. Tissue samples from the lungs, liver, and spleen, however, tested negative for herpesvirus infection. The gammaherpesvirus detected herein is similar to other isolates found in several areas worldwide in different cetacean species. This is the first reported case of gammaherpesvirus infection in dolphins from the eastern Mediterranean Sea, indicative of the need for long-term assessments to create viral infections databases in cetaceans, especially in a climate change context, which is likely to intensify infectious disease outbreaks in marine mammals in the future.

Unraveling Metabolite Provisioning to Offspring Through Parental Fluids: A Case Study of the Brazilian Guitarfish, Pseudobatos horkelii.

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, ß-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.

Elasmobranch-associated microbiota: a scientometric literature review.

Elasmobranchs provide greatly relevant ecosystem services for the balance of the environments in which they are inserted. In recent decades, sharp population declines have been reported for many species in different regions worldwide, making this taxonomic group currently one of the most threatened with extinction. This scenario is almost entirely due to excessive fishing pressure, but any contributing factor that may cause additional mortality to populations must be mapped and monitored. In a fast-changing world, emerging marine pollution associated with climate change display the potential to increase the spread of infectious agents. These can, in turn, lead to mortality events, both directly and indirectly, by reducing immune responses and the physical and nutritional condition of affected individuals. In this context, the present study aimed to analyze data concerning elasmobranch-associated microbiota, identifying study trends and knowledge gaps in order to direct future studies on this topic of growing relevance for the health of wild populations, as well as individuals maintained in captivity, considering the zoonotic potential of these microorganisms.