Carcharhinus Brevipinna Research Articles

Multidecadal fishers’ knowledge reveals overexploitation of sharks in southeastern Brazil

Abstract Assessing the impacts caused by fisheries requires long-term data series and continuous landing monitoring, which are still scarce in several low and middle-income countries. Alternative approaches, such as fishers’ local ecological knowledge (LEK) have been employed to assess the history of marine resources and overcome the challenges of missing data. We documented temporal changes over the last 60 years in small-scale fisheries in Arraial do Cabo, Brazil. Interviews with 155 fishers revealed the capture of six shark species (one genus), all under extinction risk according to the global and the national Red Lists. Among these, Carcharhinus brevipinna, Carcharhinus plumbeus, and Isurus oxyrinchus are commercially important. While LEK suggests an increase in fishing efforts, with new fishing grounds emerging after 2006, the number of individuals caught has decreased over time. Historical shark exploitation has led to substantial declines in the catches of C. plumbeus and C. brevipinna, which have rare occurrences in the region. Although landing data are critical information for building local fisheries management plans and setting conservation strategies, monitoring in the region is discontinuous and should be prioritized by public policies.

A new species of Phoreiobothrium Linton, 1889 (Cestoda: Onchoproteocephalidea) from the spinner shark, Carcharhinus brevipinna (Valenciennes) off the coast of KwaZulu-Natal, South Africa.

The extreme sparsity of collection efforts in many parts of the word, including southern Africa, leaves a vast hidden diversity of marine cestode species, such as species of Phoreiobothrium. The examination of a common South African coastal-pelagic shark species, Carcharhinus brevipinna (Valenciennes), resulted in the discovery of a new species of Phoreiobothrium Linton, 1889. Phoreiobothrium martini sp. n. is undoubtedly different from all other congeners in several morphological characteristics, however, it is most easily distinguished from other species by its total length, the size of its hooks, and the number of post vaginal testes. The addition of P. martini sp. n. increases the total number of valid species of Phoreiobothrium to 20 worldwide. Furthermore, P. martini sp. n. marks the description of representatives of only the second onchoproteocephalidean genus from southern Africa, therefore expanding the generic biogeographical representation and introducing new host associations. Apart from the description of this new species of cestode, the discovery of additional species of Phoreiobothrium will be beneficial regarding future ecological investigations. With the high degree of host-specificity found amongst species of Phoreiobothrium, species such as P. martini sp. n. could be used as sentinel species for the accurate identification, separation and diagnosis of commonly misidentified shark species.

Morphology, Morphometrics, and Shark Conservation Status at TPI Sibolga City, North Sumatra Province

Sharks are predatory animals that dwell near coral reefs and swim at the ocean's bottom. Since the inclusion of many shark species in CITES Appendix II status in 2013, shark groups have become a global issue. This is owing to shark fishing's high exploitation, both as a target capture and as bycatch. It is divided into eleven fisheries management areas, one of which is WPPNRI 572, according to the Regulation of the Minister of Maritime Affairs and Fisheries of the Republic of Indonesia Number 18/PERMEN-KP/2014 concerning the State Fisheries Management Area of the Republic of Indonesia, hereinafter abbreviated as WPPNRI. The Indian Ocean waters west of Sumatra, as well as the Sunda Strait, are included in this area. Because it faces the high seas, notably the Indian Ocean, Sumatra's west coast is a key area of the Indonesian sea. The city of Sibolga is strategically important as one of the key entry points for utilizing the potential of western Sumatra's waters. This study was place during August and September of 2021. The goal of this study was to identify sharks landed through TPI Sibolga City in North Sumatra Province, describe their morphology and morphometrics, and describe their conservation status using IUCN and CITES criteria. Squalus chloroculus, Nebrius ferrugineus, Carcharhinus brevipinna, Carcharhinus falciformis, Carcharhinus melanopterus, Carcharhinus sorrah, Rhizoprionodon acutus, Rhizoprionodon oligolinx, and Sphyrna lewini were among the 310 sharks successfully landed in the TPI, according to the study's findings. The overall length variable has the strongest tendency, according to the results of the Principal Component Analysis Scree Plot. C. brevipinna, C. falciformis, C. melanopterus, C. sorrah, and T. obesus are shark species with comparable morphometric features. According to the IUCN, the conservation status of S. lewini is Critical or Threatened (EN). The status of N. ferrugineus is Very Vulnerable (VU). Near Threatened (NT) status for S. chloroculus, C. brevipinna, C. falciformis, C. melanopterus, C. sorrah, and T. obesus. Less Worrying Status was assigned to R. acutus and R. oligolinx (LC). While the trading status of sharks based on CITES, particularly C. falciformis, C. melanopterus, and S. lewini, are included in the Appendix II list, which denotes species that are not threatened with extinction but could be affected if trade continues without regulation

Length‐weight and length‐length relationships for eight shark species from Indonesian waters

Length-weight and length-length relationships (LWRs and LLRs) for eight species of sharks were estimated using fish specimens caught in commercial fishery during 2018–2021 and landed at three fishing ports (Tanjung Luar Fish Landing Port-Lombok, Muncar Coastal Fishing Port-Banyuwangi and Sungai Kakap Fish Landing Port-Pontianak). The LWRs for Hemipristis elongata, Lamiopsis tephrodes and Pseudocarcharias kamoharai as well as the LLR for P. kamoharai reported in this study have not appeared on FishBase. This study also improved the LWRs and LLRs for other species. In addition, this study updated the maximum total length records for Carcharhinus brevipinna, Hemigaleus microstoma, H. elongata, Hexanchus nakamurai and L. tephrodes.

On the presence of the spinner shark Carcharhinus brevipinna (Müller & Henle, 1839) (Chondrichthyes: Carcharhinidae) in Maldivian waters

We present the first confirmed report on the presence of spinner shark, Carcharhinus brevipinna, in Maldivian waters. The species was observed in front of Kooddoo’s harbour, in Villingili pass, Northern Huvadhoo Atoll, Southern Maldives in March 2020.

Connecting post-release mortality to the physiological stress response of large coastal sharks in a commercial longline fishery.

Bycatch mortality is a major factor contributing to shark population declines. Post-release mortality (PRM) is particularly difficult to quantify, limiting the accuracy of stock assessments. We paired blood-stress physiology with animal-borne accelerometers to quantify PRM rates of sharks caught in a commercial bottom longline fishery. Blood was sampled from the same individuals that were tagged, providing direct correlation between stress physiology and animal fate for sandbar (Carcharhinus plumbeus, N = 130), blacktip (C. limbatus, N = 105), tiger (Galeocerdo cuvier, N = 52), spinner (C. brevipinna, N = 14), and bull sharks (C. leucas, N = 14). PRM rates ranged from 2% and 3% PRM in tiger and sandbar sharks to 42% and 71% PRM in blacktip and spinner sharks, respectively. Decision trees based on blood values predicted mortality with >67% accuracy in blacktip and spinner sharks, and >99% accuracy in sandbar sharks. Ninety percent of PRM occurred within 5 h after release and 59% within 2 h. Blood physiology indicated that PRM was primarily associated with acidosis and increases in plasma potassium levels. Total fishing mortality reached 62% for blacktip and 89% for spinner sharks, which may be under-estimates given that some soak times were shortened to focus on PRM. Our findings suggest that no-take regulations may be beneficial for sandbar, tiger, and bull sharks, but less effective for more susceptible species such as blacktip and spinner sharks.

Ontogenetic Patterns of Elemental Tracers in the Vertebrae Cartilage of Coastal and Oceanic Sharks

As predators, coastal and oceanic sharks play critical roles in shaping ecosystem structure and function, but most shark species are highly susceptible to population declines. Effective management of vulnerable shark populations requires knowledge of species-specific movement and habitat use patterns. Since sharks are often highly mobile and long-lived, tracking their habitat use patterns over large spatiotemporal scales is challenging. However, the analysis of elemental tracers in vertebral cartilage can describe a continuous record of the life history of an individual from birth to death. This study examined trace elements (Li, Mg, Mn, Zn, Sr, and Ba) along vertebral transects of five shark species with unique life histories. From most freshwater-associated to most oceanic, these species include Bull Sharks (Carcharhinus leucas), Bonnethead Sharks (Sphyrna tiburo), Blacktip Sharks (Carcharhinus limbatus), Spinner Sharks (Carcharhinus brevipinna), and Shortfin Mako Sharks (Isurus oxyrinchus). Element concentrations were compared across life stages (young-of-the-year, early juvenile, late juvenile, and adult) to infer species-specific ontogenetic patterns of habitat use and movement. Many of the observed elemental patterns could be explained by known life history traits: C. leucas exhibited clear ontogenetic changes in elemental composition matching expected changes in their use of freshwater habitats over time. S. tiburo elemental composition did not differ across ontogeny, suggesting residence in estuarine/coastal regions. The patterns of elemental composition were strikingly similar between C. brevipinna and C. limbatus, suggesting they co-occur in similar habitats across ontogeny. I. oxyrinchus elemental composition was stable over time, but some ontogenetic shifts occurred that may be due to changes in migration patterns with maturation. The results presented in this study enhance our understanding of the habitat use and movement patterns of coastal and oceanic sharks, and highlights the applicability of vertebral chemistry as a tool for characterizing shark life history traits.

Vulnerability Assessment of Pelagic Sharks in the Western North Pacific by Using an Integrated Ecological Risk Assessment.

Simple SummaryA new integrated ecological risk assessment (ERA) including the IUCN Red List category, the body weight variation trend of 1989–2011 with large sample size (n > 678,000), and the inflection point of population growth curve coupled with the ERA was developed to assess the impact of longline fishery on the pelagic sharks in the western North Pacific. The intrinsic rate of population growth was used to estimate the productivity, and the susceptibility was estimated by the multiplication of the catchability, selectivity, and post-capture mortality. Five groups were identified based on the cluster analysis coupling with non-parametric multi-dimensional scaling. Rigorous management measures are recommended for the scalloped hammerhead, silky, and spinner shark at highest risk, setting total allowable catch quota is recommended for the bigeye thresher, and sandbar shark, and a consistent monitoring scheme is suggested for the smooth hammerhead, shortfin mako, pelagic thresher, oceanic whitetip, and dusky shark.The vulnerability of 11 pelagic shark species caught by the Taiwanese coastal and offshore longline fisheries in the western North Pacific were assessed by an ecological risk assessment (ERA) and 10 of the 11 species was assessed by using an integrated ERA developed in this study. The intrinsic rate of population growth was used to estimate the productivity of sharks, and the susceptibility of sharks was estimated by the multiplication of the catchability, selectivity, and post-capture mortality. Three indices namely, the IUCN Red List category, the body weight variation trend, and the inflection point of population growth curve coupled with ERA were used to conduct an integrated ERA. The results indicated that the scalloped hammerhead is at the highest risk (group 1), followed by the silky shark, and the spinner shark at high risk (group 2). The bigeye thresher, and sandbar shark fall in group 3, the smooth hammerhead falls in group 4, and the shortfin mako, pelagic thresher, oceanic whitetip, and dusky shark fall in group 5. Rigorous management measures for the species in groups 1 and 2, setting total allowable catch quota for group 3, and consistent monitoring schemes for groups 4 and 5 are recommended.

Inside the mouth of sharks: Comparative data on the morphology of the oropharyngeal cavity

Oropharyngeal dermal denticles and oral papillae are present throughout the oropharyngeal cavity, and incorporate the use of taste buds to orally process and evaluate the food items, whereas oral denticles are thought to provide a form of protection against abrasion during food consumption and improve ventilation efficiency. Herein, are compared the microstructure of the oropharyngeal denticles and papillae of large predatory requiem sharks (Carcharhinidae) (Carcharhinus brevipinna, C.leucas, C. limbatus, C.obscurus, C.signatus, and Galeocerdo cuvier), under scanning electron microscopy. The results revealed that the largest oral denticles were found in adults of C. signatus, followed by juveniles of G. cuvier, C. leucas, and C. obscurus, respectively. Oral papillae were found to be larger in G. cuvier, C. signatus, and in C. leucas, and all these specimens presented round-shaped papillae. The higher denticles densities were found in the oral cavity of C. signatus, however, this species presented the lowest density of papillae. Carcharhinus limbatus presented the second highest rate of denticles density, followed by G. cuvier, C. obscurus, C. leucas, and C. brevipinna. The highest density of papillae was found in C. brevipinna, indicating that the density of denticles is inversely proportional to the papillae distribution, the same as we observed in C. signatus. The denticles density seems to be higher as the animal increases in size, as we observed in adult specimens of C. signatus, and this shark presented two different morphologies of denticles, different from the other species studied here. This may suggest that densities and sizes of these structures differ as the animals grow, expressed by the prey spectrum availability and the dietary shifts due to the distinct habitat which the species are associated during their life cycles.

REDESCRIPTION OF CATHARIOTREMA SELACHII (MACCALLUM, 1916) JOHNSTON AND TIEGS, 1922 (MONOGENOIDEA: MONOCOTYLIDAE), EMENDATION OF MONOTYPIC CATHARIOTREMA JOHNSTON AND TIEGS, 1922, AND PROPOSAL OF CATHARIOTREMATINAE N. SUBFAM. BASED ON MORPHOLOGICAL AND NUCLEOTIDE EVIDENCE.

We herein redescribe the enigmatic Cathariotrema selachii (MacCallum, 1916) Johnston and Tiegs, 1922 based on the holotype, paratypes, and newly collected specimens infecting the olfactory organ of 5 shark species from the Gulf of Mexico (all new host records): scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834) (Carcharhiniformes: Sphyrnidae); great hammerhead shark, Sphyrna mokarran (Rüppell, 1837); blacktip shark, Carcharhinus limbatus (Müller and Henle, 1839) (Carcharhiniformes: Carcharhinidae); spinner shark, Carcharhinus brevipinna (Müller and Henle, 1839); and Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson, 1836) (Carcharhinidae). These specimens were morphologically indistinguishable from each other and from MacCallum's holotype and paratypes. Those sequenced had identical first internal transcribed spacer (ITS1) and large subunit ribosomal DNA (28S) nucleotide sequences. As such, C. selachii infects sharks of 2 orders (Carcharhiniformes, Lamniformes) and 3 families (Carcharhinidae, Sphyrnidae, Lamnidae) in the Northwestern Atlantic Ocean (type locality) and Gulf of Mexico (new records herein). This report is the first of new specimens of C. selachii in the Atlantic Ocean Basin in 95 yr and corrects long-standing error cascades and ambiguities concerning the morphology and systematic placement of C. selachii. Considering morphology and nucleotide-based phylogenetic evidence (28S, Bayesian analysis), we herein emend monotypic CathariotremaJohnston and Tiegs, 1922 and propose Cathariotrematinae Bullard n. subfam. for it and 4 other genera (all formerly assigned to Merizocotylinae Johnston and Tiegs, 1922). These genera comprise species infecting only the nose of sharks (monotypic Cathariotrema, SqualotremaKearn and Green, 1983 and SeptitremaKheddam, Chisholm, and Tazerouti, 2020 plus 3 species of TriloculotremaKearn, 1993) and nose of a chimaera (monotypic HolocephalocotyleDerouiche, Neifar, Gey, Justine, and Tazerouti, 2019). Cathariotrematinae differs from Merizocotylinae by having a 3-part attachment organ and by lacking open loculi that symmetrically encircle a cluster of >2 loculi in the center of the haptor. Monophyletic Cathariotrematinae (with sequences representing species of Cathariotrema, Triloculotrema, and Holocephalocotyle only) was sister to monophyletic Merizocotylinae, which together were sister to monophyletic Calicotylinae Monticelli, 1903. These subfamilies comprise a monophyletic group of monocotylids that have a double vagina and infect extrabranchial, enclosed niches (urogenital system, body cavity, olfactory chamber/nose) on their shark, ray, and chimaera hosts (all other monocotylids have a single vagina and infect the gill or body surfaces of rays only). Monocotylinae Taschenberg, 1879 and Decacotylinae Chisholm, Wheeler, and Beverley-Burton, 1995 were recovered as monophyletic. Heterocotylinae Chisholm, Wheeler, and Beverley-Burton, 1995 remained paraphyletic. We accept ParacalicotyleSzidat, 1970.

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.

Complete mitochondrial genome and phylogenetic analysis of the copper shark Carcharhinus brachyurus (Günther, 1870)

Copper shark (Carcharhinus brachyurus Günther, 1870) is one of the most widely distributed but least known species in the family Carcharhinidae. Herein, we report the first complete mitogenome of C. brachyurus. The overall structure of the 16,704 bp C. brachyurus mitogenome was similar to that of other Carcharhinus species and showed the highest average nucleotide identity (97.1%) with the spinner shark (Carcharhinus brevipinna). Multigene phylogeny using 13 protein-coding genes (PCGs) in the mitogenome resolved C. brachyurus clustered with other species within the genus; the overall tree topology was congruent with recent phylogenetic studies of this species. These results provide important information for conservation genetics and further evolutionary studies of sharks.

Identifying shark species responsible for fisheries depredation off Southeast Queensland, Australia.

Anecdotal reports from fishers in Southeast Queensland, Australia suggest that shark depredation is a significant issue, however little is known about which species are responsible for depredating catches. This research aimed to identify depredating species in Southeast Queenslandline based fisheries, by undertaking a genetic analysis of depredated samples collected by commercial, charter and recreational fishers. The genetic analysis successfully identified ten depredating sharks, all from the genus Carcharhinus (19.2% success). The species identified using mitochondrial DNA included five C. leucas (bull sharks), two C. plumbeus (sandbar sharks), one C. amboinensis (pigeye shark), one C. brevipinna (spinner shark) and one unconfirmed C. plumbeus/C. altimus (bignose shark). While many species of Carcharhinus have been found to depredate catches in Australia, C. leucas has not been highlighted until this research as a potential problematic species. The optimised protocol allowed for the confident identification of shark species responsible for depredation in fisheries using frozen fish samples donated by fishers.

Identification and Delineation of Essential Habitat for Elasmobranchs in Estuaries on the Texas Coast

Essential habitat is required for a given species to complete its lifecycle and includes habitat for breeding, feeding, and growth. Estuaries provide essential habitat for many fishes, including elasmobranchs, particularly as nurseries. Shore-based, gillnet surveys have documented ten elasmobranch species (sharks and batoids) inhabiting Texas estuaries; however, limitations in the methodology, spatial, and temporal scope employed mean the role of these estuaries as elasmobranch nurseries remains uncertain. Therefore, an alternative sampling technique was implemented to survey open water locations in two Texas estuaries during the peak time of putative elasmobranch nursery usage (May to October). Ten species of elasmobranch were observed, including a shark, Carcharhinus porosus, and batoid species, Hypanus americanus, that were not documented in previous surveys. The most commonly encountered species, Carcharhinus brevipinna, comprised 45% of individuals caught, in contrast to previous surveys of these estuaries, in which the species was less than 1% of the total elasmobranch catch. The results revealed a distinction between sharks and batoids in terms of the life history stages present, as well as the depths and distances from the tidal inlet of areas in which they were encountered. Young-of-the-year and small juvenile Carcharhinus brevipinna and Sphyrna lewini were observed across multiple years and in multiple months within years at one site, suggesting that one of the sampled estuaries functions as a nursery. Although putative nurseries for these species have been identified elsewhere in the world, estuaries serving as nursery grounds in the western Gulf of Mexico are not well described.

Use of historical data to assess changes in the vulnerability of sharks

Shark populations have declined worldwide. However, the lack of data for most species makes it difficult to use conventional population assessments to estimate their status. The productivity and susceptibility analysis (PSA) has been recommended for elasmobranchs as it is a data-poor assessment that uses the best available information of the species and their fisheries to determine their vulnerability. A historical characterisation was performed to define the most important periods for the shark fishery in Campeche, southern Gulf of Mexico, and a PSA was conducted to determine the vulnerability of the eleven most important commercial shark species in each three periods. The periods were defined as: local commercialisation (1940–1979), when all species had their lowest vulnerability values, and Carcharhinus leucas, Negraprion brevirostris, and Sphyrna mokarran were classified as highly vulnerable; developed industry (1980–1998) when there was an increase of the fishing pressure, and most small species changed from low to moderate vulnerability and the large coastal sharks scored their highest vulnerability values; and declining industry (1999–2018), when all species had lower vulnerability values than in the developed industry period. However, Carcharhinus brevipinna, Ginglymostoma cirratum, N. brevisrostris, C. leucas, and S. mokarran were still classified as highly vulnerable and could be suffering the accumulative effects of decades of fishing pressure. This multidisciplinary approach serves to identify the most vulnerable species throughout the history of the fishery and to understand the vulnerability values within a historical context, avoiding the shifting baseline syndrome.

Four New Species of Paraorygmatobothrium (Eucestoda: Phyllobothriidea) from Sharks of the Gulf of Mexico and the Atlantic Ocean, with Comments on Their Host Specificity

Four new species of Paraorygmatobothrium are described from carcharhinid shark species from the Gulf of Mexico and the U.S. coast of the northwestern Atlantic Ocean. Paraorygmatobothrium bullardi n. sp. is described from Carcharhinus brevipinna as its type host, and from Carcharhinus acronotus and Carcharhinus limbatus. Paraorygmatobothrium campbelli n. sp. is described from Rhizoprionodon terraenovae. Paraorygmatobothrium deburonae n. sp. is described from Carcharhinus isodon as its type host, as well as from C. brevipinna, C. limbatus, and R. terraenovae. Paraorygmatobothrium mattisi n. sp. is described from R. terraenovae as its type host, and from C. brevipinna and C. limbatus. These 4 species differ from other species of Paraorygmatobothrium and from each other in bothridial microthrix shape, and in various combinations of features such as the total length of the worm, apical sucker size, bothridial musculature, proglottid number, testes number, and genital pore position. Difficulty in differentiating these 4 species from one another, and from other species of Paraorygmatobothrium, points to limitations in the use of morphology alone to recognize species diversity in this genus. A phylogenetic analysis of Paraorygmatobothrium and related genera, based on partial (D1-D3) 28S rDNA sequence data, confirms that the genus is not monophyletic. Genetic distances of COI revealed that sequence divergence between species of Paraorygmatobothrium is generally at least an order of magnitude larger than COI divergence within a species. Patterns of host use for 3 of the new species are consistent with previous findings that point to a lack of host specificity in Paraorygmatobothrium.

Assessing trophic flexibility of a predator assemblage across a large estuarine seascape using blood plasma stable isotope analysis

The northcentral Gulf of Mexico (nGoM) encompasses a range of environments that support a speciose predatory assemblage. Large predatory species are often viewed as trophically-analogous, sharing similar isotopic niches. To investigate the regional and seasonal isotopic variability of a predator assemblage across the coastal waters of the nGoM (Louisiana, Mississippi, and Alabama), we analyzed the stable isotopes of carbon, nitrogen, and sulfur using a fast turnover tissue, blood plasma, for seven dominant predator species. Carbon, nitrogen, and sulfur isotope values varied regionally, with a significant interaction between region and season for nitrogen and sulfur. Species' isotopic niches varied regionally, as well as seasonally, leading to varying levels of isotopic niche overlap among species. Blacktip sharks Carcharhinus limbatus and Atlantic sharpnose sharks Rhizoprionodon terraenovae in particular demonstrated flexibility in their isotopic relationships, whereas blacknose sharks C. acronotus maintained a more consistent isotopic niche regardless of region or season. No biologically significant overlap was observed for blacknose sharks, bull sharks C. leucas, or spinner sharks C. brevipinna, suggesting that these species occupy distinct isotopic space. Overlap calculations using two isotopes (carbon and nitrogen) produced markedly higher overlap versus three isotopes (carbon, nitrogen, and sulfur), which demonstrates that predatory roles may be oversimplified when using only carbon and nitrogen. These findings highlight the value of examining seasonal variation in trophic roles using fast turnover tissues and provide the first triple-isotope characterization of a common predatory assemblage in the northcentral Gulf of Mexico.

DNA analysis of elasmobranch products originating from Bangladesh reveals unregulated elasmobranch fishery and trade on species of global conservation concern.

Trade involving elasmobranch products in Bangladesh is a four-decade-long practice in large scale and there is little understanding of its impact on species composition, population, and subsequent conservation. Capacity for monitoring and identification is lacking in landing and shark processing centres. A rapid survey and collection of tissue samples were performed in three landings and nine shark processing centres between 2016 and 2017 in the south-eastern coastal region of Bangladesh. Sequencing for a 707-bp fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was used to assess the taxonomic status and species composition from 71 elasmobranch tissue samples collected from the shark processing centre only. Good quality COI sequences were obtained for 34 specimens representing 21 species—the majority of which are threatened with extinction. A total of ten species of sharks (Carcharhinus brevipinna, C. amboinensis, C. leucas, C. sorrah, C. amblyrhynchoides, Chiloscyllium burmensis, Galeocerdo cuvier, Rhincodon typus, Scoliodon laticaudus, and Sphyrna lewini), eleven species of rays (Aetomylaeus maculatus, Gymnura poecilura, Mobula mobular, M. kuhlii, Neotrygon indica, Pateobatis uarnacoides, Rhinoptera javanica, and R. jayakari), including three species of guitarfish (Glaucostegus granulatus, G. obtusus, and G. typus), were identified. Four species (14.7% of samples) were found to be listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Appendix II. Sixteen species (59% of the specimens) were threatened with extinction according to IUCN Red List, whereas 41% were data deficient or not assessed. The results have important implications for the management of regional fisheries and the conservation of elasmobranchs as they 1) represent a preliminary understanding of elasmobranch diversity in trade; 2) depict a lack of awareness and monitoring; and 3) demonstrate a need for urgent monitoring and regulation of elasmobranch trade in Bangladesh.

A Note on Associations Observed between Sharks and Teleosts

We report herein on novel observations of associations between 2 teleost species and a variety of shark species in the Gulf of Mexico. Using underwater video, we observed Decapterus punctatus (Round Scad) and Chloroscombrus chrysurus (Atlantic Bumper) associating with both Carcharhinus limbatus (Blacktip Shark) and Carcharhinus brevipinna (Spinner Shark). We also observed Round Scad associating with Carcharhinus acronotus (Blacknose Shark). Both Round Scad and Atlantic Bumpers schooled around and followed these sharks. We observed Round Scad in schools averaging 54 individuals that tended to stay posterior to the pectoral fins of the shark. These observations prompted a novel on-line image survey wherein we found that Round Scad were associated with 3 additional shark species. Online media platforms have not been commonly utilized for data collection, and to our knowledge, this is the first study to conduct a Google Image survey to obtain data supporting interspecific associations. This paper is also the first report of an apparent symbiosis between various shark species with Round Scad and with Atlantic Bumpers. There are few reports of associations with sharks aside from well-known examples, such as Echeneis naucrates (Sharksucker), Naucrates ductor (Pilotfish), and Labroides spp. (cleaner wrasses). These results provide additional information to the body of literature about symbioses between top predators, such as sharks, and teleosts.

Shark pelagic longline fishery in the Gulf of Gabes: Inter-decadal inspection reveals management needs

This study explores the status of exploited shark populations in the Gulf of Gabes in relation to fishing pressure, based on data pertaining to shark longline fishery, collected during two periods. Catch data from 48 and 96 pelagic longline sets collected, respectively, during 2007/2008 and 2016/2017, were used to compare species composition and catch rates between periods. Four species were recorded during 2007/2008, while 11 additional species of pelagic and demersal elasmobranchs along with teleosts were fished during 2016/2017. Elasmobranch species dominated the catches with 94% and 99.3% in terms of specimens number, respectively, during 2016/2017 and 2007/2008. The sandbar shark, Carcharhinus plumbeus, was the predominant species in catch (>84% of all fishes) during both periods. Two other species of sharks, Carcharhinus brevipinna and Isurus oxyrinchus, were relatively common, while the other species were a minor component. Despite the increase in terms of diversity pertaining to species captured during 2016/2017, the nominal catch rates of elasmobranch and C. plumbeus decreased by 39.17% and 42.21%, respectively, suggesting populations’ declines. In addition, size distribution analyses revealed that this fishery may opportunistically operate on breeding and nursery areas, which affect main species over most of their life stages. The mortality and hooking location proportions were species-specific, with some species having significant percentages of live specimens at the time of haulback, providing an opportunity to release the sensitive life stages. Given the described state of shark exploitations in the Gulf of Gabes, urgent and efficient fishery regulation measures and conservation strategies, together with further investigations, are required to allow changing the unregulated shark longline fishery to a sustainable one.