A Novel Mini-DNA Barcoding Assay to Identify Processed Fins from Internationally Protected Shark Species

There is a growing need to identify shark products in trade, in part due to the recent listing of five commercially important species on the Appendices of the Convention on International Trade in Endangered Species (CITES; porbeagle, Lamna nasus, oceanic whitetip, Carcharhinus longimanus scalloped hammerhead, Sphyrna lewini, smooth hammerhead, S. zygaena and great hammerhead S. mokarran) in addition to three species listed in the early part of this century (whale, Rhincodon typus, basking, Cetorhinus maximus, and white, Carcharodon carcharias). Shark fins are traded internationally to supply the Asian dried seafood market, in which they are used to make the luxury dish shark fin soup. Shark fins usually enter international trade with their skin still intact and can be identified using morphological characters or standard DNA-barcoding approaches. Once they reach Asia and are traded in this region the skin is removed and they are treated with chemicals that eliminate many key diagnostic characters and degrade their DNA (“processed fins”). Here, we present a validated mini-barcode assay based on partial sequences of the cytochrome oxidase I gene that can reliably identify the processed fins of seven of the eight CITES listed shark species. We also demonstrate that the assay can even frequently identify the species or genus of origin of shark fin soup (31 out of 50 samples).     

Characterization of the pelagic shark‐fin trade in north‐central Chile by genetic identification and trader surveys

Shark fins have become a highly valued commodity with the major Asian fin‐trade centres supplied from global sources, including Chile. With growing concerns about the resilience of shark populations to heavy fishing pressure, there is a need for better information on shark landings to aid management efforts. In the widespread absence of shark landing records especially by species, monitoring the fin trade has been proposed as a way to assess species exploitation levels. Here, the first species assessment of the Chilean shark‐fin trade was provided. The goals of this study were to (1) determine the species composition and relative species proportion of sharks utilized in the fin trade, (2) determine the relationship between fin trader market names and species and (3) assess trader accuracy in identifying shark fin species based on fin photographs. Fins were analysed from two different fin drying facilities (n = 654) (secaderos) and two fin‐storage warehouses (n = 251). In contrast to official government landing records that only document four species in the landings, molecular species identification of the fins demonstrated that at least 10 pelagic shark species are present in the north‐central Chilean shark fin trade: Alopias superciliosus, Alopias vulpinus, Carcharhinus obscurus, Galeorhinus galeus, Isurus oxyrinchus, Isurus paucus, Lamna nasus, Prionace glauca, Sphyrna lewini, Sphyrna zygaena. The species composition of the fins from the secaderos was P. glauca (83·9%), I. oxyrinchus (13·6%), L. nasus (1·7%) and A. superciliosus (0·2%). There was generally good agreement between market names and single shark species for the trade categories ‘Azulejo’, ‘Tiburon’, ‘Tintorera’, ‘Cola de zorro’ and ‘Martillo’. In contrast, the market category ‘Carcharhinus’ consisted of a mixture of at least five species. The molecular results also identified two species (S. lewini and I. paucus) not previously recorded in Chilean waters. The fin identification survey given to nine regional traders demonstrated that they were highly accurate in recognizing pictures of fins from P. glauca and I. oxyrinchus. The overall strong concordance between market categories and fins from single species and the trader accuracy in survey fin identification suggests that monitoring the Chilean fin trade by market names will provide a reasonably accurate picture of the volume of sharks landed by species.     

The Species and Origin of Shark Fins in Taiwan’s Fishing Ports,Markets, and Customs Detention: A DNA Barcoding Analysis

The increasing consumption of shark products, along with the shark’s fishing vulnerabilities, has led to the decrease in certain shark populations. In this study we used a DNA barcoding method to identify the species of shark landings at fishing ports, shark fin products in retail stores, and shark fins detained by Taiwan customs. In total we identified 23, 24, and 14 species from 231 fishing landings, 316 fin products, and 113 detained shark fins, respectively. All the three sample sources were dominated by Prionace glauca, which accounted for more than 30% of the collected samples. Over 60% of the species identified in the fin products also appeared in the port landings, suggesting the domestic-dominance of shark fin products in Taiwan. However, international trade also contributes a certain proportion of the fin product markets, as four species identified from the shark fin products are not found in Taiwan’s waters, and some domestic-available species were also found in the customs-detained sample. In addition to the species identification, we also found geographical differentiation in the cox1 gene of the common thresher sharks (Alopias vulpinus), the pelagic thresher shark (A. pelagicus), the smooth hammerhead shark (Sphyrna zygaena), and the scalloped hammerhead shark (S. lewini). This result might allow fishing authorities to more effectively trace the origins as well as enforce the management and conservation of these sharks.     

Genetic profiling reveals illegal international trade in fins of the great white shark, <Emphasis Type="Italic">Carcharodon carcharias</Emphasis>

Great white sharks are protected by national legislation in several countries, making this species the most widely protected elasmobranch in the world. Although the market demand for shark fins in general has continued to grow, the value and extent of utilization of white shark fins in trade has been controversial. We combine law enforcement with genetic profiling to demonstrate that illegal trade in fins of this species is occurring in the contemporary international market. Furthermore, we document the presence of fins from very young white sharks in the trade, suggesting a multiple-use market (food to trophies) exists for fins of this species. The presence of small fins in the trade contradicts the view that white shark fins have market value only as large display trophies, and not as food. Our findings indicate that effective conservation of protected shark species will require international management regimes that include monitoring of the shark fishery and trade on a species-specific basis.     

The biology and conservation status of the large hammerhead shark complex: the great,scalloped, and smooth hammerheads

Hammerhead sharks are among the most intriguing yet imperiled groups of large sharks globally. Until recently, our understanding of their biology, movements, diet, and life histories was challenged by a lack of studies. In recent years there has been a surge of published studies on this group of sharks, incorporating new information on age and growth, behavior, and the threats they face. Here we summarize and compare what is known on the biology and conservation of the three largest species of hammerhead sharks: the great hammerhead (Sphyrna mokarran), the scalloped hammerhead (Sphyrna lewini), and the smooth hammerhead (Sphyrna zygaena). We chose these species since they are the most well-studied of the hammerheads, and also because they are commonly captured in target and non-target fisheries worldwide. Thus, we also discuss population trends and the vulnerabilities of each species, and make recommendations for future studies on these fascinating and complex elasmobranch fishes.     

Identification of young‐of‐the‐year great hammerhead shark Sphyrna mokarran in northern Florida and South Carolina

Two sharks, visually identified in the field as young‐of‐the‐year (YOY) scalloped hammerhead Sphyrna lewini, were identified as great hammerhead Sphyrna mokarran based on nuclear‐encoded single nucleotide polymorphisms (SNP) and sequences of mtDNA. Individuals were captured and released in Bulls Bay, SC, and Saint Joseph Bay, FL, in 2013 and 2014, respectively. These findings indicate S. mokarran may be pupping in or around these areas and highlight new regions that may be a productive focus for future research on early life history of S. mokarran.     

Discovery of a multispecies shark aggregation and parturition area in the Ba Estuary,Fiji Islands

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species‐specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here, we present a fisheries‐independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location's role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north‐western Viti Levu) was assessed with a gillnet‐ and longline‐based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68% open or semihealed), mean sizes of individuals (±SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered.” Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small‐scale environmental drivers of shark abundance. The data suggests a tendency for species‐specific spatial use, both horizontally (i.e., between sampling areas) and vertically (i.e., across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.     

Vulnerability to longline fisheries of three hammerhead shark Sphyrna species in the south‐western and equatorial Atlantic Ocean

Catch and effort data from 29 418 longline sets from Brazilian tuna longline vessels operating in the south‐western and equatorial Atlantic Ocean between 2004 and 2011 were analysed to investigate the distribution, catch rate and size of three species of hammerhead sharks (Sphyrna lewini, Sphyrna mokarran and Sphyrna zygaena). During that period, 6172 hammerhead sharks were caught. Among the elasmobranchs, the highest percentage of hammerhead sharks were caught in 2007, when they accounted for 3·90% of the group, while the lowest value of 0·40% was recorded in 2010. In general, the spatial distribution of the mean catch per unit effort (CPUE) by years and quarters showed a trend of higher catches near the equatorial region and in southern Brazil. The nominal mean CPUE was 0·12 Sphyrna spp. 1000⁻¹ hooks, with the highest value being recorded in 2007 (0·30 Sphyrna spp. 1000⁻¹ hooks). The standardized yearly CPUE estimated by a generalized linear model assuming a zero inflated negative binomial (ZINB) distribution were not much different from nominal values. Of the 205 sexed specimens, 117 were females and 88 were males, resulting in a sex ratio with a predominance of females (1·30:1·00), although not statistically significant. The total length of females ranged from 1200 to 2800 mm and of males from 1100 to 3100 mm. Juvenile hammerhead sharks represented 82 and 54% of the sexed female and male specimens, respectively.     

Historical records reveal potential extirpation of four hammerhead sharks (Sphyrna spp.) in Mexican Pacific waters

Populations of hammerhead sharks (Sphyrna and Eusphyra) have declined in many regions of the world. Six of the eight hammerheads known to date are distributed in the Mexican Pacific: S. corona, S. lewini, S. media, S. mokarran, S. tiburo and S. zygaena. These species, with exception of S. corona, were abundant in the Gulf of California in 1960s. I analyze records from fishery-dependent and fishery-independent surveys, and records from ichthyological collections to determine the presence and frequency of hammerheads in the Mexican Pacific. The most frequent hammerheads in fishery-dependent and fishery-independent surveys were S. lewini and S. zygaena. It appears that S. media, S. mokarran and S. tiburo might have been extirpated from the Gulf of California. In the last two decades, records of S. mokarran (n = 61) were restricted to Central and Southern Mexican Pacific, and records of S. tiburo (n = 3) and S. media (n = 3) were restricted to the Southern region. Given the continued fishing pressure, inferred declines and the probable extirpation of populations, S. tiburo and S. media should be reassessed for the IUCN red list as Endangered or Critically Endangered. Sphyrna corona should be reassessed as Endangered or Critically Endangered, because it is endemic to the Eastern Pacific and recent records have been obtained only from Colombian waters. The Endangered status of S. mokarran is confirmed for this region.     

Global estimates of shark catches using trade records from commercial markets

Despite growing concerns about overexploitation of sharks, lack of accurate, species-specific harvest data often hampers quantitative stock assessment. In such cases, trade studies can provide insights into exploitation unavailable from traditional monitoring. We applied Bayesian statistical methods to trade data in combination with genetic identification to estimate by species, the annual number of globally traded shark fins, the most commercially valuable product from a group of species often unrecorded in harvest statistics. Our results provide the first fishery-independent estimate of the scale of shark catches worldwide and indicate that shark biomass in the fin trade is three to four times higher than shark catch figures reported in the only global data base. Comparison of our estimates to approximated stock assessment reference points for one of the most commonly traded species, blue shark, suggests that current trade volumes in numbers of sharks are close to or possibly exceeding the maximum sustainable yield levels.     

Notes on the long‐term transport of the scalloped hammerhead shark (Sphyrna lewini)

The capture and transport of scalloped hammerhead sharks (Sphyrna lewini Griffith and Smith, 1834) historically has represented a difficult, expensive, and uncertain undertaking for the public aquarium community. In this study, techniques were developed to improve the successful long‐term transport of S. lewini by mitigating some of the deleterious effects associated with hyperactivity and impaired swimming patterns. The relationship between the transport vessel size and shark sizes, numbers, and swimming behavior was considered when formulating the transport regime. By balancing these factors and adopting a comprehensive water treatment method, it was possible to extend the duration of a successful transport by up to 60 hr. Implications for the future transport of S. lewini and other free‐swimming sharks are discussed. Zoo Biol 21:243–251, 2002. © 2002 Wiley‐Liss, Inc.     

French naiad (Bivalvia: Margaritiferidae,Unionidae) species distribution models: prediction maps as tools for conservation

The aim of this study was to determine whether juvenile scalloped hammerhead sharks (Sphyrna lewini) use the south-eastern Gulf of California as a nursery and feeding area. This information could help lay the groundwork required for the conservation of this endangered species. To address this, we carried out stable isotope (δ¹⁵N and δ¹³C) and stomach content analyses of sharks caught between 2000 and 2004 in Mazatlan, Mexico. Stomach contents and δ¹³C values indicated that S. lewini is a predator that feeds on benthic prey near the coast. Differences in δ¹⁵N average values between sizes classes (<100 vs. >100 cm) suggest that there was an ontogenetic change in this shark’s feeding habits and also in their living environment (from benthic areas to pelagic areas). The trophic position indicated that S. lewini is a tertiary consumer, but with a high degree of trophic plasticity, and thus, different trophic roles, highlighting the importance of this predator as a regulator of prey populations. Finally, the linear isotopic relationship between S. lewini and its prey indicates a long residency within the Mazatlan area. Our results demonstrate that the south-eastern Gulf of California is a nursery area that offers abundant food for juvenile scalloped hammerhead sharks.     

Feeding ecology and trophic comparisons of six shark species in a coastal ecosystem off southern Brazil

The diets of six shark species, Sphyrna lewini, Sphyrna zygaena, Carcharhinus obscurus, Carcharhinus limbatus, Rhizoprionodon lalandii and Galeocerdo cuvier, were investigated in a subtropical coastal ecosystem of southern Brazil. Stomach content data were obtained to assess foraging niche segregation and ontogenetic shifts in the diets of these sharks. Five of the shark species off the Paraná coast were ichthyophagous, with the exception of S. zygaena, which was teutophagous. With the exception of G. cuvier, which had a generalist diet, the other five species displayed specialization in their feeding. Ontogenetic shifts were observed in C. obscurus and S. lewini with large individuals consuming elasmobranchs. Owing to the diet overlap between C. obscurus and S. lewini, C. obscurus and C. limbatus and R. lalandii and C. limbatus, future studies on the spatial and temporal distributions of these species are needed to understand the extent of competitive interactions.     

Stomach content analysis of juvenile, scalloped hammerhead shark Sphyrna lewini captured off the coast of Mazatlán, Mexico

We quantified the diet of juvenile, scalloped hammerhead shark Sphyrna lewini in the area off Mazatlan, Sinaloa, Mexico, to understand their feeding ecology this shark. The prey species of Sphyrna lewini were identified and quantified from stomach content analysis. In addition, we determined the variations between genders. During two fishing seasons (2000–2001 and 2001–2002), we analyzed 232 stomachs, of which 85% contained food. The trophic spectrum was composed of three species of cephalopods, six of crustaceans and 19 species of fish from mainly pelagic and benthic habitats. According to the Index of Relative Importance (%IRI), the cephalopod Loliolopsis diomedeae with IRI = 18%, fish of the family Carangidae IRI = 25% and family Synodontidae IRI = 19% constituted the main prey in general. The trophic niche width was <0.4, which indicated that S. lewini juveniles in this area feed on a wide range of prey items, though they showed a preference for a few prey items.     

应用脂肪酸组成研究热带东太平洋同域中上层鲨鱼营养生态位分化

物种对食物资源利用方式的差异,即营养生态位分化是物种共存的先决条件之一,对种间营养生态位的比较研究有助于了解同域分布物种的共存机制。脂肪酸组成可反映生物较长时间尺度的摄食信息,对探讨物种间营养生态位分化具有重要指示作用。热带东太平洋主要栖息有8种大型中上层鲨鱼,大青鲨(Prionace glauca)、大眼长尾鲨(Alopias superciliosus)、镰状真鲨(Carcharhinus falciformis)、长鳍真鲨(Carcharhinus longimanus)、浅海长尾鲨(Alopias pelagicus)、尖吻鲭鲨(Isurus oxyrinchus)、路氏双髻鲨(Sphyrna lewini)和锤头双髻鲨(Sphyrna zygaena),通过比较其肌肉脂肪酸组成,分析种间食性差异,营养关系及营养生态位分化。结果表明,尖吻鲭鲨营养级相对较高,大青鲨相对较低。3种鼠鲨与5种真鲨存在食性差异或栖息地隔离。浅海长尾鲨与大眼长尾鲨营养生态位重叠程度较高,存在激烈的资源竞争。大青鲨与镰状真鲨生态位宽度较大,表征其对环境的可塑性较强;尖吻鲭鲨和路氏双髻鲨生态位宽度较小,表现为其食性的特化。本研究解释了脂肪酸组成分析在鲨鱼摄食研究中的潜在应用,对分析大洋性鲨鱼的营养生态位分化,资源分配方式及同域共存机制有一定的应用价值。     

Age,growth and reproductive biology of the silky shark,Carcharhinus falciformis,and the scalloped hammerhead,Sphyrna lewini,from the northwestern Gulf of Mexico

Synopsis The silky shark, Carcharhinus falciformis, and scalloped hammerhead, Sphyrna lewini, represent >80% of the shark by-catch of the winter swordfish/tuna longline fishery of the northwestern Gulf of Mexico. This catch represents a potential supplemental fishery, yet little is known of the life histories of the two species. This report relates reproductive biology data to age and growth estimates for 135 C. falciformis and 78 S. lewini. Unlike other regional populations, C. falciformis in the Gulf of Mexico may have a seasonal 12 month gestation period. Males mature at 210–220 cm TL (6–7 yr); females at >225 cm TL (7–9 yr). Application of age at length data for combined sexes produced von Bertalanffy growth model parameter estimates of L_∞ = 291 cm TL, K = 0.153, t₀ = −2.2 yr. Adult male S. lewini outnumbered adult females in catches because of differences in the distributions of the sexually segregated population. Males mature at 180 cm TL (10 yr); females at 250 cm TL (15 yr). von Bertalanffy parameter estimates for combined sexes of this species were L_∞ = 329 cm TL, K = 0.073, t_o = −2.2 yr.     

Head Morphology and Electrosensory Pore Distribution of Carcharhinid and Sphyrnid Sharks

Selection to maximize electroreceptive search area might have driven evolution of the cephalofoil head morphology of hammerhead sharks (family Sphyrnidae). The enhanced electrosensory hypothesis predicts that the wider head of sphyrnid sharks necessitates a greater number of electrosensory pores to maintain a comparable pore density. Although gross head morphology clearly differs between sphyrnid sharks and their closest relatives the carcharhinids, a quantitative examination is lacking. Head morphology and the distribution of electrosensory pores were compared between a carcharhinid, Carcharhinus plumbeus, and two sphyrnid sharks, Sphyrna lewini and S. tiburo. Both sphyrnids had greater head widths than the carcharhinid, although head surface area and volume did not differ between the three species. The raked head morphology of neonatal S. lewini pups, presumably an adaptation to facilitate parturition, becomes orthogonal to the body axis immediately post-parturition whereas this change is much less dramatic for the other two species. The general pattern of electrosensory pore distribution on the head is conserved across species despite the differences in gross head morphology. Sphyrna lewini has a mean of 3067 ± 158.9 SD pores, S. tiburo has a mean of 2028 ± 96.6 SD pores and C. plumbeus has a mean of 2317 ± 126.3 SD pores and the number of pores remains constant with age. Sphyrnids have a greater number of pores on the ventral surface of the head whereas C. plumbeus has an even distribution on dorsal and ventral surfaces. The greater number of pores distributed on a similar surface area provides S. lewini pups with a higher density of electrosensory pores per unit area compared to C. plumbeus pups. The greater number of ampullae, the higher pore density and the larger sampling area of the head combine to provide hammerhead sharks with a morphologically enhanced electroreceptive capability compared to comparably sized carcharhinids.     

Potential expansion in the spatial distribution of subtropical and temperate west Australian sharks

Fishery-dependent and -independent data collected since 1975 were examined to explore the spatial distribution of 30 shark and ray species in the west coast of Australia. Bigeye sixgill (Hexanchus nakamurai), tiger (Galeocerdo cuvier) and spinner (Carcarhinus brevipinna) sharks, and scalloped hammerhead (Sphyrna lewini) were observed >1000 and 300 km to the east of the edge of their reported distributions. Broadnose sevengill sharks (Notorhyncus cepedianus) and southern sawsharks (Pristiophorus nudipinnis) were observed >1000 km to the west of the edge of their reported distributions. Our study highlights the value of collecting and examining long time-series of data for understanding the spatial distribution of large marine predators.     

Big catch,little sharks: Insight into Peruvian small‐scale longline fisheries

Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small‐scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. Of these, 70.6% were blue sharks (Prionace glauca), 28.4% short‐fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k‐selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods.     

Rapid and Simultaneous Identification of Body Parts from the Morphologically Similar Sharks Carcharhinus obscurus and Carcharhinus plumbeus (Carcharhinidae) Using Multiplex PCR

Many commercially exploited carcharhinid sharks are difficult to identify to species owing to extensive morphological similarities. This problem is severely exacerbated when it comes to identifying detached shark fins, and the finless and headless shark carasses typically sold in markets. To assist in the acquisition of urgently needed conservation and management data on shark catch and trade, we have developed a highly streamlined approach based on multiplex polymerase chain reaction (PCR) that uses species-specific primers derived from nuclear ribosomal ITS2 sequences to achieve rapid species identification of shark body parts. Here we demonstrate the utility of this approach for identifying fins and flesh from two globally distributed, morphologically very similar carcharhinid sharks (Carcharhinus obscurus and Carcharhinus plumbeus) intensively targeted in fisheries worldwide, and often confused for each other even as whole animals. The assay is conducted in a 4-primer multiplex format that is structured to simultaneously achieve the following efficiency and cost-reduction objectives: it requires only a single-tube amplification reaction for species diagnosis, it incorporates an internal positive control to allow detection of false-negative results, and it is novel in that it allows species identification even when DNAs from two species are combined in the same tube during the PCR reaction. The latter innovation reduces the required effort for screening a set of unknown samples by 50%. The streamlined approach illustrated here should be amenable for use in a shark conservation and management context where large numbers of samples typically need to be screened; the approach shown may also provide a model for a rapid diagnostic method applicable to species identification in general. Received September 15, 2000; accepted December 15, 2000