Prionace Research Articles

Mercury stable isotopes suggest reduced foraging depth in oxygen minimum zones for blue sharks

Oxygen minimum zones (OMZs) are currently expanding across the global ocean due to climate change, leading to a compression of usable habitat for several marine species. Mercury stable isotope compositions provide a spatially and temporally integrated view of marine predator foraging habitat and its variability with environmental conditions. Here, we analyzed mercury isotopes in blue sharks Prionace glauca from normoxic waters in the northeastern Atlantic and from the world's largest and shallowest OMZ, located in the northeastern Pacific (NEP). Blue sharks from the NEP OMZ area showed higher Δ199Hg values compared to sharks from the northeastern Atlantic, indicating a reduction in foraging depth of approximately 200 m. Our study suggests for the first time that blue shark feeding depth is altered by expanding OMZs and illustrates the use of mercury isotopes to assess the impacts of ocean deoxygenation on the vertical foraging habitat of pelagic predators.

Trophic niche partitioning of five sympatric shark species in the tropical eastern Pacific Ocean revealed by multi-tissue fatty acid analysis

Fatty acid (FA) analysis of consumer tissues has recently shown utility in drawing further inferences about trophic niche dynamics of marine predators such as sharks. In this study, we examined liver, plasma, and muscle FAs in five coexisting pelagic sharks (blue (Prionace glauca), silky (Carcharhinus falciformis), bigeye thresher (Alopias superciliosus), pelagic thresher (Alopias pelagicus), and smooth hammerhead (Sphyrna zygaena)) inhabiting the tropical eastern Pacific Ocean. Results showed complex inter- and intra-individual and tissue variation among the five shark species. Based on multivariate analysis of the muscle FAs, P. glauca and C. falciformis have the largest FA niche widths, indicating diverse feeding habits or habitat isolation, whereas A. pelagicus and S. zygaena occupied a narrower niche width, reflecting increased trophic specialization. High percentages of muscle FA niche overlap indicated strong resource competition between S.zygaena and C. falciformis and a degree of dietary isolation by P. glauca. Interpretations of feeding ecology differed based on the analysis of plasma FAs, which could be attributed to higher dietary FA turnover rates. The liver was deemed unsuitable to examine FA niche metrics based on high and unexplained intra-specific variance in liver FAs as well as the unique lipid metabolism in chondrichthyans. Overall, our multi-tissue approach revealed the magnitude of potential competitive interactions among coexisting tropical shark species. It also expanded our understanding of inter-tissue variability and best practices when using FA analysis to estimate trophic niche metrics of sharks.

Extraction of Biocompatible Collagen From Blue Shark Skins Through the Conventional Extraction Process Intensification Using Natural Deep Eutectic Solvents.

The disposal of large amounts of skin waste resulting from the blue shark fishing industry presents several industrial and environmental waste management concerns. In addition, these marine subproducts are interesting sources of collagen, a fibrous protein that shows high social and economic interest in a broad range of biomedical, pharmaceutical, and cosmetic applications. However, blue shark wasted skins are a poorly explored matrix for this purpose, and conventional collagen recovery methodologies involve several pre-treatment steps, long extraction times and low temperatures. This work presents a new green and sustainable collagen extraction approach using a natural deep eutectic solvent composed of citric acid:xylitol:water at a 1:1:10 molar ratio, and the chemical characterization of the extracted collagen by discontinuous electrophoresis, thermogravimetric analysis, Fourier transformed infrared spectroscopy and circular dichroism. The extracted material was a pure type I collagen, and the novel approach presented an extraction yield 2.5 times higher than the conventional one, without pre-treatment of raw material and reducing the procedure time from 96 to 1 h. Furthermore, the in vitro cytotoxicity evaluation, performed with a mouse fibroblasts cell line, has proven the biocompatibility of the extracted material. Overall, the obtained results demonstrate a simple, quick, cheap and environmentally sustainable process to obtain marine collagen with promising properties for biomedical and cosmetic applications.

Marine origin biomaterials using a compressive and absorption methodology as cell-laden hydrogel envisaging cartilage tissue engineering.

In the recent decade, marine origin products have been growingly studied as building blocks complying with the constant demand of the biomedical sector regarding the development of new devices for Tissue Engineering and Regenerative Medicine (TERM). In this work, several combinations of marine collagen-chitosan-fucoidan hydrogel were formed using a newly developed eco-friendly compressive and absorption methodology to produce hydrogels (CAMPH), which consists of compacting the biopolymers solution while removing the excess of water. The hydrogel formulations were prepared by blending solutions of 5% collagen from jellyfish and/or 3% collagen from blue shark skin, with solutions of 3% chitosan from squid pens and solutions of 10% fucoidan from brown algae, at different ratios. The biopolymer physico-chemical characterization comprised Amino Acid analysis, ATR-FTIR, CD, SDS-PAGE, ICP, XRD, and the results suggested the shark/jellyfish collagen(s) conserved the triple helical structure and had similarities with type I and type II collagen, respectively. The studied collagens also contain a denaturation temperature of around 30-32°C and a molecular weight between 120 and 125kDa. Additionally, the hydrogel properties were determined by rheology, water uptake ability, degradation rate, and SEM, and the results showed that all formulations had interesting mechanical (strong viscoelastic character) and structural stability properties, with a significant positive highlight in the formulation of H3 (blending all biopolymers, i.e., 5% collagen from jellyfish, 3% collagen from skin shark, 3% chitosan and 10% of fucoidan) in the degradation test, that shows a mass loss around 18% over the 30days, while the H1 and H2, present a mass loss of around 35% and 44%, respectively. Additionally, the in vitro cellular assessments using chondrocyte cells (ATDC5) in encapsulated state revealed, for all hydrogel formulations, a non-cytotoxic behavior. Furthermore, Live/Dead assay and Phalloidin/DAPI staining, to assess the cytoskeletal organization, proved that the hydrogels can provide a suitable microenvironment for cell adhesion, viability, and proliferation, after being encapsulated. Overall, the results show that all marine collagen (jellyfish/shark)-chitosan-fucoidan hydrogel formulations provide a good structural architecture and microenvironment, highlighting the H3 biomaterial due to containing more polymers in their composition, making it suitable for biomedical articular cartilage therapies.

How Well Do 'Catch-Only' Assessment Models Capture Catch Time Series Start Years and Default Life History Prior Values? A Preliminary Stock Assessment of the South Atlantic Ocean Blue Shark Using a Catch-Based Model.

Simple SummaryBlue shark species are at the top of the list of captured bycatch sharks in most tuna and tuna-like fisheries. As a consequence, their populations have been declining due to overfishing; thus, there is a need for the assessment of their stocks to better understand blue sharks’ stock status. Most bycatch species lack sufficient data for traditional stock assessment models to be implemented. Blue sharks in the South Atlantic have been assessed in the past using a state-space production model. Given the development of new assessment models and the use of up-to-date data, their stock status was evaluated using a new state-space production model (CMSY++). We used different catch time series, abundance indices and priors to measure the intrinsic growth rate r to evaluate their influence on the outputs of CMSY++. We identified from many scenarios that the blue shark stock in the South Atlantic may be witnessing overfishing and is being overfished.CMSY++, an improved version of the CMSY approach developed from Catch-MSY which uses a Bayesian implementation of a modified Schaefer model and can predict stock status and exploitation, was used in the present study. Evaluating relative performance is vital in situations when dealing with fisheries with different catch time series start years and biological prior information. To identify the influences of data inputs on CMSY++ outputs, this paper evaluated the use of a nominal reported catch and a reconstructed catch dataset of the South Atlantic blue shark alongside different priors of the blue shark’s productivity/resilience (r) coupled with different indices of abundance. Results from the present study showed that different catch time series start years did not have a significant influence on the estimation of the biomass and fishing reference points reported by CMSY++. However, uninformative priors of r affected the output results of the model. The developed model runs with varying and joint abundance indices showed conflicting results, as classification rates in the final year changed with respect to the type of index used. However, the model runs indicated that South Atlantic blue shark stock could be overfished (B2020/Bmsy = 0.623 to 1.15) and that overfishing could be occurring (F2020/Fmsy = 0.818 to 1.78). This result is consistent with the results from a previous assessment using a state-space surplus production model applied for the same stock in 2015. Though some potential could be observed when using CMSY++, the results from this model ought to be taken with caution. Additionally, the continuous development of prior information useful for this model would help strengthen its performance.

Evaluation of the shark fisheries along the Coastline of Ghana, West Africa

The decline in traditionally valuable fish stocks, coupled with an increased demand for shark fins and meat has caused many fishermen to target sharks. However, there is limited information on the fishing practices, gears, and catch distribution for the shark fisheries. This study used a semi-structured interview to characterize the shark fisheries and techniques used to catch sharks as well as the catch statistics and trade in fifteen coastal communities along the Eastern, Central, and Western coasts of Ghana. Out of the 470 fishers interviewed, 46% were specialized shark fishers while the remaining 54% landed sharks as bycatch. Specialized shark fishers captured between 7–10 individual sharks per fishing trip while by-catch shark fishers captured between 1–5 sharks. The shark species harvested include the blue shark, thresher shark, common and sand tiger, bull shark, short and longfin mako shark, hammerhead, and milk shark. Fishers along the eastern coast mostly capture sharks as bycatch, while those along the central and western coast of Ghana target sharks with specialized fishing gears. The catch data obtained from the fishers indicated higher shark landings and was linked to the development of longlines and drift gill nets with hooks attached to the footrope that target sharks, and are usually deployed along the western coastlines of Ghana. Nearly all the shark species captured in the study communities were listed by the IUCN as either “Endangered”, “Critically Endangered” or “Vulnerable”. Among fishers who target sharks, 74% stated that shark populations were declining and were spending more effort to capture the fish. Specialized shark fishers indicated a poor perception and attitude towards shark conservation along the entire coastline of the country and are not in support of shark conservation. It is recommended that the capture and trade in these species should be closely monitored to prevent the extinction of vulnerable populations.

Mercury bioaccessibility in fish and seafood: Effect of method, cooking and trophic level on consumption risk assessment

The bioaccessible Hg fraction in fish and seafood commonly present in the Mediterranean diet was assessed through three distinct in vitro extraction schemes. Each extraction method provided different results, highlighting the lack of a universal methodology to estimate mercury (Hg) bioaccessibility in those matrices. Bioaccessible Hg fractions ranged from 10 to nearly 90% of total mercury (T-Hg) and increased in predator species (Swordfish - Xiphias gladius, Blue Shark - Prionace glauca and Tuna - Thunnus sp.). Among the three extractions tested, the Unified Bioaccessibility Method (UBM) provided the highest estimation of Hg bioaccessibility for consumers. The tested cooking procedures (frying, grilling and steaming) considerably reduced the bioaccessible fraction. Results indicate that bioaccessible Hg found in ingested fish and seafood is far below the levels set by the current safety risk assessment legislation. These findings highlight the importance of integrating bioaccessibility measurements in food safety legislation.

Preliminary study on spatio-temporal variations of five giant and 17 large fish species around the Korean peninsula from 2011 to 2016

Although giant and large fish species are highly important as a keystone species in the marine ecosystem, there have been no or few studies on their spatio-temporal variations around the Korean peninsula. For this, we analyzed daily reports made by observers at 57 fishery landing sites in Korea over 6 years, from 2011 to 2016. In total, 153 fish species were re-identified based on photos and descriptions recorded by Korean observers, of which five species were classified as a giant fish over 5 m in maximum total length (MTL) and 17 species as a large fish from 3 m to 5 m MTL according to the data presented by Froese & Pauly (2021). Among the giant and large fish species, Mola mola was the most abundant species, with 75 individuals landed as by-catch. The second most abundant species was Isurus oxyrinchus (31), followed by Mobula mobular (23), Lamna ditropis (17), Masturus lanceolatus (16), Sphyrna zygaena (14), and Prionace glauca (12). As a result of cluster analysis based on the number of individuals of giant and large fish species by year and sea, six years were separated into two clusters (2011–2013 vs. 2014–2016), with high contribution of M. mola, I. oxyrinchus, and M. lanceolatus; and three seas were separated into two clusters (eastern + southern seas vs. western sea), with high contribution of M. lanceolatus, L. ditropis, and I. oxyrinchus. The largest number of M. mola accounted for 64% of the total in 2014 and 2016, and 71% in summer (June–August). It is assumed to have a correlation between seawater temperature fluctuation and the occurrence of giant and large fish species. Our study highlights importance of longterm monitoring of giant and large fish species, and can help to understand the life cycle such as natal or nursery migration of giant and large fish species around the Korean peninsula.

Global-Scale Environmental Niche and Habitat of Blue Shark (Prionace glauca) by Size and Sex: A Pivotal Step to Improving Stock Management

Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.

Optimal setting time and season increase the target and reduce the incidental catch in longline fisheries: a Bayesian beta mixed regression approach

Abstract Sustainable fisheries' managers increasingly seek to implement measures that reduce the mortality of threatened species while maintaining or increasing catch of target species. Our study proposed a simple management option for optimizing fishing over daily and seasonal scales to maximize catch success while protecting non-target species in pelagic longline fisheries. We used Bayesian beta mixed regression models to describe the effects of setting times and seasonality on catches in a pelagic longline fishery in the southwest South Atlantic Ocean (SWAO). Targeted species (swordfish, blue shark, and albacore tuna) are typically captured in fully nocturnal sets (started between 16 and 00 h), whereas shortfin mako shark and loggerhead turtles are typically captured during partially nocturnal sets (started between 00 and 04 h); probably a response to hook depth and circadian behaviours. The results suggest that it is feasible to use only fully nocturnal sets to target preferred species while reducing incidental catch of non-target species. The catch of target species was higher in austral winter, explained by the northward displacement of the subtropical convergence in the SWAO during this season. These results provide a baseline for bycatch mitigation strategies in pelagic longline fisheries at regional and global scales.

Evaluation of the Kenya long line pelagic fishery: Temporal variation in fishing effort and catch rates

Pelagic fishes support a vital part of the local and export production and trade at global, regional, and local levels. In the Western Indian Ocean, pelagic fishes are mainly exploited by purse-seiners and long-line fishing vessels operating in national exclusive economic zones and international waters. Catch data from these vessels is often not adequately evaluated to determine the variation of catches and the state of the exploited stocks. This study evaluates the Kenya long line fishery between 2016 and 2020 to determine catch rates, temporal variation over time, and the key species’ maximum sustainable yield (MSY). The catches were dominated by Xiphias gladius (44.7%), Thunnus albacares (24.4%), Thunnus obesus (10.9%), and Prionace glauca (7.7%). Catch rates were significantly different among years, months, vessels, and depths for all species except for X. gladius and P. glauca, whose catch rates did not significantly differ at different depths. The catch rates for X. gladius, T. obesus, and T. albacares were higher during the northeast monsoon season, while P. glauca had higher catch rates during the southeast monsoon season. The maximum sustainable yield (MSY) was higher than the annual catches for the four species. We recommend catch rates be monitored over a more extended period for trend comparison and future work to consider discards encountered during fishing. We recommend seasonal closures for management, especially for the vessels targeting tunas and swordfish to conduct fishing during the NEM season when the catch rates are higher. There is a need for future work to focus on hook selectivity for the long-line fisheries along the Kenya EEZ.

Species composition, seasonality and biological characteristics of Western Ghana’s elasmobranch fishery

Despite the fact that elasmobranchs are now targeted in artisanal fisheries in the wake of continuous declines of teleosts in Ghana, data on any aspects of these fisheries are poor. This study aims to document the spatial and temporal variation, and biological composition of elasmobranchs in five key elasmobranch-dominated fishing communities in Western Ghana, which include Adjoa, Axim, Busua, Dixcove and Shama. A total of 2157 elasmobranchs comprising 1414 sharks and 743 rays, belonging to 34 species in 15 families, were recorded over the course of 9 months. Prionace glauca (81.2%) and Raja parva (29.3%) were the dominant shark and ray species, respectively. Shama had the highest mean shark catch (33.3 ± S.D 29.7), followed by Dixcove (19.1 ± 14.7) and Axim (18.2 ± 12.4). However, Axim exhibited the greatest mean ray catch (25.8 ± 10.6), followed by Adjoa (10.9 ± 3.8) and Busua (9.6 ± 5.4). The greatest relative catch and species richness for all the sites was documented in the minor rainy season (August to November). Sexual segregation was typical among most of the common elasmobranch species landed. This study serves as a baseline for monitoring future changes in the artisanal shark and ray fisheries in Western Ghana.

What Is in Your Shark Fin Soup? Probably an Endangered Shark Species and a Bit of Mercury

Simple SummaryShark fin soup is consumed by many Asian communities throughout the world and is one of the main drivers of the demand for shark fin. The demand for shark products has seen shark populations decline by as much as 70%. The fins found in soups break down into a fibrous mass meaning that identifying the species of shark that a fin came from is impossible by visual methods. Here, we use molecular techniques to identify the species of sharks found in bowls of soup collected in Singapore. We identified a number of endangered species in the surveyed soups, and many of these species have been shown to contain high levels of mercury, a potent neurotoxin. It is highly likely that consumers of shark fin soup are consuming levels of mercury that are above safe allowable limits, and at the same time are contributing to the massive declines in global shark populations.Shark fin soup, consumed by Asian communities throughout the world, is one of the principal drivers of the demand of shark fins. This near USD 1 billion global industry has contributed to a shark population declines of up to 70%. In an effort to arrest these declines, the trade in several species of sharks is regulated under the auspices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Despite this legal framework, the dried fins of trade-regulated sharks are frequently sold in markets and consumed in shark fin soup. Shark fins found in soups break down into a fibrous mass of ceratotrichia, meaning that identifying the species of sharks in the soup becomes impossible by visual methods. In this paper, we use DNA barcoding to identify the species of sharks found in bowls of shark fin soup collected in Singapore. The most common species identified in our samples was the blue shark (Prionace glauca), a species listed as Near Threatened on the International Union for Conservation of Nature (IUCN) Red List with a decreasing population, on which scientific data suggests catch limits should be imposed. We identified four other shark species that are listed on CITES Appendix II, and in total ten species that are assessed as Critically Endangered, Endangered or Vulnerable under the IUCN Red List of Threatened Species. Globally, the blue shark has been shown to contain levels of mercury that frequently exceed safe dose limits. Given the prevalence of this species in the examined soups and the global nature of the fin trade, it is extremely likely that consumers of shark fin soup will be exposed to unsafe levels of this neurotoxin.

Drivers of at-vessel mortality of the blue shark (Prionace glauca) and oceanic whitetip shark (Carcharhinus longimanus) assessed from monitored pelagic longline experiments

Elasmobranchs make up a significant part of bycatch in pelagic longline fisheries, whose induced mortality can be a major threat to endangered species. It is therefore crucial to understand the drivers of at-vessel mortality (AVM) for this fishing gear to enhance postrelease survival. To this end, we analysed scientific data collected during monitored longline fishing experiments conducted in French Polynesia to ( i) estimate AVM for each species based on bootstrapped samples and ( ii) to assess AVM drivers using multivariate logistic regression models for the blue shark ( Prionace glauca) and oceanic whitetip shark ( Carcharhinus longimanus). We found that AVM varies widely between species. Oceanic whitetip sharks are more likely to die when caught in waters outside their comfort temperature range, and their odds of survival increase with body length. For the blue shark, the only driver related to AVM is hooking duration. These results indicate that to reduce the AVM of these two species, the vertical distribution of hooks and soak duration should be considered as mitigation measures related to pelagic longlining.

Marine‐climate interactions with the blue shark (Prionace glauca) catches in the western coast of Baja California Peninsula, Mexico

AbstractFishery and size data by sex of 28,110 blue sharks (Prionace glauca) from 2162 longline sets documented by observers on board 204 fishery trips from the industrial fleet based in Ensenada, Mexico during 2006–2016, were used to conduct a spatial–temporal analysis of the catch‐per‐unit‐effort (CPUE) and its relationship with climate indices along the west coast of the Baja California Peninsula. Catch length analysis by maturity groups indicated catches were composed mainly by juvenile females (58–199 cm TL) and males (60–179 cm TL). Relationships of seasonal CPUE with sea surface temperature (SST) and Chlorophyll‐a (Chl) were analyzed determining aggregations were in areas characterized by oceanographic physical processes. From the exploratory analysis of annual correlations of climate indices with CPUE, the local climate SanDiAs Index explained most variation in CPUE. A generalized additive model (GAM) with 13 predictor variables was applied to gain insight on their relationship with the total CPUE by size and sex groups. The model explained 50.5% of the total blue shark CPUE and 65.5% for juvenile females. The GAM results revealed blue shark CPUE is influenced by five relevant factors: SST, NPGO, year, latitude with distance to coast and quarter interactions, and hooks set. There is a trend to increase or decrease of CPUE when compared with the delay of NEI and SanDiAs indices in more than 1 year. Local and regional climate indices can be successful tools for forecasting blue shark catches in the Northwestern Mexican Pacific.

Occurrence and population structure of sharks in two ecologically or biologically significant marine areas off north‐eastern Brazil

Abstract Ecologically or Biologically Significant Marine Areas (EBSAs) are rare, and highly important sites to the life history of a number of declining shark species are endangered by fishing. The high diversity of sharks caught by fisheries is difficult to monitor due to the scarcity of information on species‐specific biological aspects (growth, maturity and fertility rate). There are two EBSAs off north‐eastern Brazil, where key species are caught, more specifically the oceanic whitetip (Carcharhinus longimanus), mako (Isurus oxyrinchus), blue (Prionace glauca) and silky (Carcharhinus falciformis) sharks. Another 23 species displaying low frequency in catches have also been recorded, many of them considered threatened according to the IUCN Red List and the Brazilian Ministry of Environment. The main purpose of this study was to generate information about shark diversity and demonstrate the role of the two EBSAs in their conservation. After analysing fishing data collected from 2000 to 2011, maps were built to categorize shark species by phases of their ontogenetic development (neonate, young and adult) based on samples of C. falciformis (n = 330), C. longimanus (n = 440), I. oxyrinchus (n = 452) and P. glauca (n = 8,176). Shark stocks comprised mainly juveniles, which raises concerns since they are considered a crucial life stage for the sustainability of shark populations. Catch monitoring also highlighted that several of the species caught are threatened and their catch is either prohibited or limited according to the Brazilian laws and international rules in place. Action plans and enforcement of laws and rules are needed to deliver the protective measures needed for shark species in these EBSAs.

Cadmium and lead levels in muscle tissue of blue shark (Prionace glauca) in the Southeastern Pacific Waters

Prionace glauca is a top predator, prone to bioaccumulate trace elements, representing the most captured elasmobranch species for human consumption in Peru. Concentrations of cadmium and lead in the edible muscle tissue of the blue shark captured in the south Peruvian coastal waters and offshore north-central Chile were determined. The Cd and Pb levels varied between 0.004 and 0.014 and 0.004 and 0.03 mg kg−1, respectively. We found direct correlation of Cd concentration with the total length, nevertheless there was no clear relationship regarding sex, seasons, and capture areas. Both metals were below the safety limits for human consumption. The target hazard quotient (THQ) values suggest that its consumption does not represent a risk to the human health. In Peru, this is only the second paper that reports Cd and Pb in sharks. We recommend increasing the sampling by including larger sharks and in other regions of the Peruvian coastline.

DNA Barcoding Identifies Endangered Sharks in Pet Food Sold in Singapore

Shark populations have declined by more than 70% over the past 50 years. These declines have largely been attributed to increases in fishing efforts. Despite increased public awareness surrounding the conservation of sharks, three-quarters of all oceanic shark species are currently considered at risk of extinction. Here, we use DNA barcoding to identify shark DNA found in pet food purchased within Singapore. We identified a number of sharks that have some degree of control over their trade exerted under the auspices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), or through their classification as threatened by the International Union for Conservation of Nature (IUCN). The most commonly identified shark was the blue shark, Prionace glauca, a species that is not listed in CITES or classified as threatened by the IUCN, but one which scientific evidence suggests is overexploited and should have its catch regulated. The second most commonly encountered species was the CITES Appendix II listed silky shark, Carcharhinus falciformis. None of the products specifically listed shark as an ingredient, listing only generic terms, such as “ocean fish,” “white fish,” and “white bait.” The vague terminology used to describe pet food ingredients, and in some cases, the mislabeling of contents, prevents consumers – in this case, pet owners – from making informed and environmentally conscious decisions; consequently, pet owners and animal lovers may unwittingly be contributing to the overfishing of endangered sharks.

Microstructure and energy dispersive diffraction reconstruction of 3D patterns of crystallographic texture in a shark centrum.

Purpose: Tomography using diffracted x-rays produces reconstructions mapping quantities such as crystal lattice parameter(s), crystallite size, and crystallographic texture, information quite different from that obtained with absorption or phase contrast. Diffraction tomography is used to map an entire blue shark centrum with its double cone structure (corpora calcerea) and intermedialia (four wedges). Approach: Energy dispersive diffraction (EDD) and polychromatic synchrotron x-radiation at 6-BM-B, the Advanced Photon Source, were used. Different, properly oriented Bragg planes diffract different x-ray energies; these intensities are measured by one of ten energy-sensitive detectors. A pencil beam defines the irradiated volume, and a collimator before each energy-sensitive detector selects which portion of the irradiated column is sampled at any one time. Translating the specimen along , and axes produces a 3D map. Results: We report 3D maps of the integrated intensity of several bioapatite reflections from the mineralized cartilage centrum of a blue shark. The axis reflection's integrated intensities and those of a reflection with no axis component reveal that the cone wall's bioapatite is oriented with its axes lateral, i.e., perpendicular to the backbone's axis, and that the wedges' bioapatite is oriented with its axes axial. Absorption microcomputed tomography (laboratory and synchrotron) and x-ray excited x-ray fluorescence maps provide higher resolution views. Conclusion: The bioapatite in the cone walls and wedges is oriented to resist lateral and axial deflections, respectively. Mineralized tissue samples can be mapped in 3D with EDD tomography and subsequently studied by destructive methods.

Mineralized collagen as a bioactive ink to support encapsulation of human adipose stem cells: A step towards the future of bone regeneration

Bioprinting – printing with incorporated living cells – has earned special attention on tissue engineering approaches, aiming to closer reproduce the 3D microenvironment of the target tissue. However, it raises extra complexity related to the need to use cell-friendly printing conditions that still comply with material printing fidelity. Inspired by the composite nano structural organization of mineralized tissues, this work reports the efficiency of the chemical approach followed to in situ mineralize blue shark skin collagen, at a nano scale level, to ultimately produce stable inks. The influence of initial cellular density was evaluated by assessing three different concentrations (2.5, 5 and 7.5 × 106 cells·ml−1) of human adipose stem cells (hASC), with the higher density of encapsulated cells presenting improved viability in a long culture term. Immunodetection of osteogenic-related markers, like RUNX2 and osteopontin, 21 days after cell culture in basal conditions confirmed the potential of the ink to be applied for osteogenic purposes, which may be associated with the success of the cell-to-ink interaction and the Ca2+ ions released from the co-precipitated hydroxyapatite. A combination of mineralized shark collagen, alginate and hASC is thus proposed as a bioactive bioink with potential properties for regeneration of bone tissue.