Lamna Nasus Research Articles

Occurrence of juvenile porbeagle sharks (Lamna nasus) in the northern coast of Spain.

Opportunistic records can provide valuable information on certain species, including the critically endangered porbeagle shark (Lamna nasus). This note documents the occurrence of three juveniles, with approximate 120-, 88-, and 85-cm fork lengths respectively, observed along the coast of Asturias, Spain, in 2024. Given the three distinct scenarios in which these records respectively occurred (incidental capture, washed ashore and stranding), they emphasize the role of citizen science in identifying potential threats to this species, particularly in early stages of life, in a region that may be important and previously overlooked.

First insights into the vertical habitat use of young porbeagles in the north-western Atlantic with implications for bycatch reduction strategies

Context For threatened marine species, data on their vertical habitat use patterns can reveal risk of interactions with fishing gear and can inform bycatch avoidance strategies. Such data are lacking for young porbeagles (Lamna nasus), which are captured as bycatch in north-western Atlantic fisheries. Aims We aimed to examine temporal patterns in diving and characterise vertical habitat use of young porbeagles during summer and autumn. Methods We used data from short-term (28-day), high-resolution (5-min interval) pop-off satellite tags attached to 14 young (young-of-the-year and 1-year-old) porbeagles to model depth use. Key results Occupied depths ranged from the sea surface to 679 m, with ambient water temperatures of −0.2 to 26°C. Diel period and season were factors related to depth use. Conclusions Sharks exhibited a diel activity pattern characterised by more extensive use of the water column during the day while remaining primarily at the surface at night. Depth use differed between seasons, with summer characterised by greater affinity for surface waters (0–10 m) compared to autumn. Implications Young porbeagles are at risk of interaction with active fisheries on the continental shelf, but interactions may be reduced by setting gear deeper at night or during summer.

New insights into the reproduction and migration of the porbeagle shark Lamna nasus (Bonnaterre 1788) in the Southwest Atlantic Ocean.

The objective of this study was to estimate the reproductive parameters of porbeagle shark in the Southwest Atlantic Ocean and thus characterize the adult fraction of this population. Therefore, 1012 specimens were measured by scientific observers on board the commercial trawl fleet operating south of 50° S. The size range of the specimens was from 77 to 292 cm fork length (LF). The mean size at maturity was estimated to be 153 cm LF for males and 172 cm LF for females. Porbeagle shark catches were recorded throughout the year, with the highest frequency occurring between November and June. The presence of pregnant females was observed from December to July, along with an increase in the average size of embryos in each litter. The information presented in this study improves the knowledge of the reproductive biology and allows to propose a migratory pattern of adult porbeagle females in the Southwest Atlantic Ocean. The likely seasonal increase in vulnerability of this shark to austral trawl fishery, despite all conservation management measures established in Argentina, underscores the importance of promoting its proper management and conservation given the need to improve understanding of porbeagle population dynamics in the Southern Hemisphere.

First Use of Free-Diving Photo-Identification of Porbeagle Shark (Lamna nasus) off the Brittany Coast, France

A large number of pelagic shark species have declined significantly in recent decades due to overfishing, bycatch, and habitat degradation. Whereas porbeagle sharks have become scarce due to a reduction in their populations around the world, recent stock evaluations are giving positive signals about the evolution of the North-Eastern Atlantic stock size. The porbeagle shark (Lamna nasus), an offshore pelagic species with a wide distribution, is designated by IUCN as Globally Vulnerable and Critically Endangered for Europe and subject to various international conservation conventions. An increasing number of observations are reported off the Brittany coast of Trégor. The ecological role of this area for the species is still unknown and greater knowledge is needed to develop and apply sustainable management measures on a local and international scale. This study represents the first use of photo-identification on porbeagle sharks in order to improve the ecological knowledge of the species in the Trégor area. These results confirm the effectiveness of this method, with 19 of the 131 individuals identified being re-sighted, indicating an interesting degree of site fidelity and showing a sex ratio of 100% females. Observations of individuals over several years allowed the researchers to discuss the relevance of the different types of marks. The findings suggest that the Trégor area off the Brittany coast serves as a seasonal residence for female porbeagle sharks, especially between May and October. This study represents a successful first step in the use of photo-identification for this species. It offers technical support for the sharing of the methodology and provides some biological knowledge allowing researchers to discuss potential sustainable management measures for the conservation of porbeagle sharks in the study area and their habitats while needed.

Application of mitochondrial gene markers and real-time PCR for the identification of Isurus spp. and Lamna nasus species

Application of mitochondrial gene markers and real-time PCR for the identification of <i>Isurus</i> spp. and <i>Lamna nasus</i> species

Stable isotopes reveal intrapopulation heterogeneity of porbeagle shark (Lamna nasus)

Porbeagle (Lamna nasus) is an ubiquist, highly mobile and long-living shark species with spatial and temporal sex and size segregation observed in catches. Porbeagle sharks were targeted by commercial fisheries in the European waters until the closure of the fishery in 2010. Most of the French fleet catches were located in Bay of Biscay, Celtic Sea and the English Channel. The aim of the study was to find out occurrences of spatial segregation within the shark population in the Northeast Atlantic Ocean based on the stable isotope method. Carbon and nitrogen stable isotopes (δ13C, δ15N) were measured in muscle of porbeagle sharks fished in the Bay of Biscay and the Celtic Sea between April and September 2008, and April and June 2009. Neither influence of sex nor ontogenic isotopic shift was detected in the sampled sharks, but muscle δ13C and δ15N values increased significantly from offshore towards coastal area, which reflected inter-areas variability. Realized isotopic niches were similar amongst offshore areas whilst in St Georges’ Channel muscle isotopic composition exhibited higher inter-individual variability. This underpins the lack of information on life history of porbeagle sharks and underlines the need of more information on the species movements to support population management in European waters.

Looking into the prevalence of bycatch juveniles of critically endangered elasmobranchs: a case study from pelagic longline and trammel net fisheries of the Asinara Gulf (western Mediterranean)

Bycatch of cartilaginous species is considered one of the main drivers for the dramatic declines observed in many populations. Pelagic longlines and passive nets impact many species depending on their life stage and habitat use. Here, we present an updated list of incidental catches collected through a 4-year fishery-dependent survey. We documented the bycatch of four critically endangered species, particularly 13 individuals of Isurus oxyrinchus, Prionace glauca, and Mobula mobular by longlines and one specimen of Lamna nasus by trammel nets in the Asinara Gulf (Northern Sardinia, Italy). As almost all specimens were juveniles or newborns, we explored and discussed the potential drivers explaining their prevalence in the sample. Despite our low sample size, of the four possible options discussed, the role of the Asinara Gulf as an Important Shark and Ray Area (ISRA) for large pelagic elasmobranch species is one worth considering.

Hai på menyen

In 2021 the University Museum of Bergen conducted an archaeological excavation at the Middle Neolithic (3500–2700 BC) site Nerlandsøy at Sunnmøre. The most surprising find was 154 teeth from Porbeagle shark (Lamna nasus) imbedded in culture layers. Teeth from this species have been found in three other sites infrom North-Western Norway, however in much lesser number than on Nerlandsøy. In this paper the shark teeth are interpreted as a hitherto unknown part of the increasing big game hunting taking place in the Middle Neolithic. The hunting activity is reflected both in the material culture, as well as in the rock art, in the region and is believed to be an important part of the social dynamics of the society.

The fossil distribution of two pelagic lamniform sharks Alopias vulpinus and Lamna nasus, from South America

ABSTRACT The fossil record of the southeastern Pacific Ocean has been scarcely studied compared to other regions. We present the detailed description of two pelagic shark species, Alopias vulpinus (common thresher) and Lamna nasus (porbeagle) (Elasmobranchii: Lamniformes), from the Neogene of South America. The fossil teeth described here were recovered from the Bahia Inglesa Formation in Caldera, northern Chile. Our study provides the first comprehensive descriptions of fossil remains of A. vulpinus from Chile and L. nasus from the Americas. The occurrence of the common thresher shark represents the first published record and description of a representative from the family Alopiidae in northern Chile, whereas the fossil remains of the porbeagle shark are recorded for the first time in Chile. This study contributes to the understanding of the past distribution of shark species in the Eastern Pacific of South America during the Neogene period. It further confirms the particular abundance of lamniform sharks in the Neogene of Chile.

Using reproductive hormones extracted from archived muscle tissue to assess maturity and reproductive status in porbeagles Lamna nasus

While lethal sampling can be the most effective technique to collect critical reproductive data for elasmobranchs, non-lethal techniques need to be validated for future use. Concentrations of reproductive hormones in plasma and muscle have been found to correlate to sexual maturity and/or reproductive cycles in oviparous as well as yolk-sac, placental, and histotrophic viviparous elasmobranchs, offering a potentially non-lethal technique to study reproduction. However, reproductive hormone analysis is scant for oophagous sharks. This study utilized muscle tissues from porbeagles Lamna nasus that were dissected for other life history studies and were stored frozen for up to 37 years to quantify testosterone (T) and estradiol (E2) concentrations in relation to previously-known maturity and reproductive stage. A total of 207 samples (92 males, 115 females) from porbeagles ranging in size from 80 to 256.5 cm fork length were analyzed. Muscle T and E2 concentrations were related to maturity and reproductive stage in porbeagles, with the highest T concentrations found in mature males during the spermatogenic season (summer) and the highest E2 concentrations found in gravid females. These results suggest muscle hormone concentrations have the potential to serve as a non-lethal proxy of reproductive stage in oophagous sharks. This study also demonstrates the value of specimen sharing and the potential for continued use of stored vertebral muscle tissue for reproductive hormone analysis in order to optimize the amount of data gained from biological samples. Future use of these methods would be particularly valuable for threatened species for which lethal sampling is restricted.

The Portuguese industrial pelagic longline fishery in the Northeast Atlantic: Catch composition, spatio-temporal dynamics of fishing effort, and target species catch rates

The multispecific and highly dynamic nature of pelagic longline fisheries demands a holistic view that will likely benefit the development of effective management strategies. This study aims to provide an integrated perspective of the Portuguese longline fishery targeting swordfish Xiphias gladius and blue shark Prionace glauca in the Northeast Atlantic, regarding fishing dynamics, target species catches and associated bycatch. Data from 896 observed fishing sets (887,641 hooks) collected between 2015 and 2020 were used in a cluster analysis to group sets according to the target species. These sets were investigated for spatio-temporal patterns, and the relationship between target species catches and environmental and operational characteristics were examined using generalized additive mixed models (GAMM). A total of 46,306 individuals from 54 species (30 fish, 11 sharks, 2 manta rays, 6 cetaceans, 2 sea turtles and 2 seabirds) were recorded. Swordfish and blue shark comprised over 88.3% of the total catch in numbers (33.6% and 54.7%, respectively). Overall, most of the fishing effort occurred west off mainland Portugal, congregated during autumn when vessels targeted mostly swordfish, and dispersed over the region during spring and summer, when vessels targeted mostly blue shark. The bycatch of sea turtles and a relatively higher diversity of bony fish species, yet low catch in terms of abundance, appeared more associated with sets identified as targeting swordfish. Recorded catch of tunas Thunnus spp. and pelagic sharks, such as the shortfin mako Isurus oxyrinchus and the porbeagle Lamna nasus, were more associated with blue shark sets. Bigeye thresher Alopias superciliosus, thresher Alopias vulpinus, pelagic stingray Pteroplatytrygon violacea and lancetfish Alepisauros ferox were found equally associated with both targeted species. Management strategies for the region are discussed in light of these new findings.

Morphological study of the oral denticles of the porbeagle shark Lamna nasus.

Oral denticles of sharks are composed by a crown, dentine covered by a layer of enameloid and pulp cavity, the same structure of the dermal denticles found across the body surface of most elasmobranchs. In addition, oral papillae and taste buds are distributed among denticles within the oropharyngeal cavity, playing a fundamental role for tasting as part of the chemosensory system of fishes. Scanning electron microscopy (SEM) has been employed as an important tool for the study of dermal denticles and other structures, as well as histology and more recently computed tomography(CT) scan analysis. Herein, the authors used two methods for the study of the morphology of the oropharyngeal cavity of Lamna nasus (Lamniformes), an oceanic and pelagic shark: SEM and CT scan. The general morphology of oral denticles studied herein is related to abrasion strength as they are diamond-shaped, lack lateral cusps and have less pronounced ridges. In addition, smooth ridges and broad rounded denticles could be related to prevent abrasion during food consumption and manipulation. Oral papillae had a round shape and were observed only under SEM. The densities of papillae were estimated in 100 per cm2 , whereas denticles were 1760 and 1230 cm2 over the dorsal and ventral regions, respectively. The high numbers of denticles are inversely proportional to papillae density; denticles seem to restrict papillae distribution. Regarding the differences between methodologies, under SEM, only the crown was visualized, as well the papillae, allowing the estimation of size and density of both structures. Nonetheless, under CT scan, the whole components of denticles were clearly visualized: different views of the crown, peduncle, basal plate, and pulp cavity. On the contrary, oral papillae were not visualized under CT due to the tissue preparation. Furthermore, both methods are complementary and were important to extract as much information as possible from denticles and papillae.

Interdisciplinary stock identification of North Atlantic porbeagle (Lamna nasus)

We conducted an interdisciplinary review of available information (i.e., genetics, life-history, and movement) to evaluate the stock structure of a previously targeted shark species, the porbeagle (Lamna nasus), in the North Atlantic. Most available information supports the conclusion that porbeagle consist of a single genetic population in the North Atlantic, which is relevant for determining species conservation status. However, the observed movement rates between the Northwest, Northeast Atlantic, and the Mediterranean appear to be low enough to consider separate spatial units for stock assessment and fishery management. The review reveals different interpretations among the organizations involved with the conservation, management, and assessments of porbeagle in the North Atlantic regarding biological population and stock boundaries. Differences in the spatial definition of management units among management organizations may pose an impediment to conserving porbeagle populations and achieving management objectives. We recommend an increased collaboration between organizations involved in highly migratory shark species as it would be beneficial for data collection, data inclusiveness, the robustness of assessments, and provide clarity for fishery managers, scientists, and the public on stocks and status. This review demonstrates that the interdisciplinary approach to stock identification is particularly valuable for data-limited species because no single approach typically has enough information to be definitive. Clearly defining management units that reflect the biological populations of porbeagle in the North Atlantic is expected to reduce uncertainty in stock assessments and help achieve current management and conservation goals of rebuilding North Atlantic porbeagle stocks.

Environmental DNA captures elasmobranch diversity in a temperate marine ecosystem

AbstractMany sharks, skates, and rays (elasmobranchs) are highly threatened by the activities of commercial fisheries, and a clear understanding of their distributions, diversity, and abundance can guide protective measures. However, surveying and monitoring elasmobranch species can be highly invasive or resource‐intensive, and utilization of non‐invasive environmental DNA‐based methods may overcome these problems. Here, we studied spatial and seasonal variation in the elasmobranch community of the Western English Channel using environmental DNA (eDNA) collected from surface and bottom waters periodically over an annual cycle (2017–2018). In total we recovered 13 elasmobranch species within eDNA samples, and the number of transformed eDNA reads was positively associated with species (hourly) catch data resolved from 105‐year time series trawl data (1914–2018). These results demonstrate the ability of eDNA to detect and semi‐quantitatively reflect the prevalence of historically dominant and rare elasmobranch species in this region. Notably, eDNA recorded a greater number of species per sampling event than a conventional trawl survey in the same area over the same sampling years (2017–2018). Several threatened species were recovered within the eDNA, including undulate ray, porbeagle shark, and thresher shark. Using eDNA, we found differences in elasmobranch communities among sampling stations and between seasons, but not between sampling depths. Collectively, our results suggest that non‐invasive eDNA‐based methods can be used to study the spatial and seasonal changes in the diversity and abundance of whole elasmobranch communities within temperate shelf habitats. Given the threatened status of many elasmobranchs in human‐impacted marine environments, eDNA analysis is poised to provide key information on their diversity and distributions to inform conservation‐focused monitoring and management.

Legacy and emerging flame retardants in sharks from the Western North Atlantic Ocean

Following the discontinuation of commercial polybrominated diphenyl ether (PBDE) mixtures, a variety of alternative flame retardants (FRs) have been developed and employed. To understand the contamination status of these emerging FRs in marine fish and wildlife, we investigated their bioaccumulation in four shark species, including shortfin mako shark (Isurus oxyrhinchus; n = 26), porbeagle (Lamna nasus; n = 4), sandbar shark (Carcharhinus plumbeus; n = 6), and common thresher (Alopias vulpinus; n = 4), from coastal and offshore waters of the western North Atlantic Ocean. Median concentrations of emerging FRs, including dechlorane analogues (i.e., dechlorane plus, Dec-602, −603, and − 604), tetrabromo-o-chlorotoluene (TBCT), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and hexabromobenzene (HBBZ), ranged from 1.4–7.4, 10.2–22.4, 1.0–16.7, and 4.1–17.7 ng/g lipid weight (lw), respectively. Although concentrations of emerging FRs were generally 1–2 orders of magnitude lower than those of legacy FRs (i.e., PBDEs, 312–800 ng/g lw and hexabromocyclododecane or HBCDD, 17.2–99.3 ng/g lw), they were detected in more than 80% of the shark livers. Analysis of available biological data indicated that fork length significantly correlated with the concentrations of ΣPBDEs, HBCDD, ΣDechloranes or TBCT in shortfin mako livers. This indicates that longer-term exposure likely results in elevated FR concentrations in sharks. Our findings suggest likely exposure of western North Atlantic fish and wildlife to several emerging FRs, including dechloranes, BTBPE, HBBZ, and TBCT. Additional studies are needed to better elucidate their potential risks to fish and wildlife as well as the variety of environmental and biological factors influencing these risks.

Species substitution and mislabeling in the swordfish (Xiphias gladius) market in Santiago, Chile: Implications in shark conservation

Food fraud and the conservation and trade of threatened species are topics of high concern. Some shark species are considered in this category by IUCN and CITES, and can enter as mislabeled or substituted in the commercialization chain. In Chile, three shark species are present as by-catch in the swordfish (Xiphias gladius) fisheries; these are sold headless, gutted, and finned, hindering their identification by morphological traits. Locally, the commercial designation for swordfish is Albacora, while the unofficial name, Albacorilla, is used in the shark products trade. Thus, DNA barcoding was used for taxonomic identification to assess food fraud incident (FFI) percentage in the swordfish market in Santiago. Muscle samples (n = 47) sold under Albacora or Albacorilla designations were obtained from supermarkets, fish markets, and open-air markets. We predicted the fraud probability by a fitted logistic regression model. The majority (91.48%) of the samples were identified as swordfish, while 6.39% were identified as porbeagle shark (Lamna nasus) and 2.13% as shortfin mako (Isurus oxyrinchus). These shark species are classified as vulnerable and endangered (IUCN), respectively, and listed in Appendix II (CITES). The FFI was 8.52%, including mislabeling (2.13%) found only in fish markets and substitution which was reported in fish markets (4.26%) and open-air markets (2.13%). No FFI were detected in supermarkets. The sales price was significant to explain FFI in the logistic model. We conclude that it is necessary to increase stakeholder awareness about shark conservation status, developing specific labelling legislation containing the scientific names and commercial designations for each shark species, and carry out effective enforcement programs of the labelling regulations using DNA-based methods.

Lamna nasus

This datasheet on Lamna nasus covers Identity.

Characterization of Halogenated Organic Compounds in Pelagic Sharks and Sea Turtles Using a Nontargeted Approach

Halogenated organic compounds (HOCs) in marine species collected from the Atlantic Ocean [3 shortfin mako (Isurus oxyrinchus) and 1 porbeagle (Lamna nasus)], and 12 sea turtles collected from the Pacific Ocean [3 loggerhead (Caretta caretta), 3 green (Chelonia mydas), 3 olive ridley (Lepidochelys olivacea), and 3 hawksbill (Eretmochelys imbricata)] were analyzed with a nontargeted analytical method using two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry. Sharks and sea turtles had distinct HOC profiles. Halogenated methoxyphenols (halo-MeOPs) were the most abundant compound class identified in sea turtle livers, while polychlorinated biphenyls (PCBs) were the most abundant in shark livers. In addition to legacy contaminants and halo-MeOPs, a total of 110 nontargeted/novel HOCs (NHOCs) were observed in the shark livers. Shortfin mako collected from the northern Gulf of Mexico contained the largest number (89) and most diverse structural classes of NHOCs. Among all NHOCs, a group of compounds with the elemental composition C14H12-nCln (n = 5-8) exhibited the highest concentrations, followed by chlorocarbazoles and tris(chlorophenyl) methanes (TCPMs). Using nontargeted workflows, a variety of known and unknown HOCs were observed, which demonstrate the need to develop more complete chemical profiles in the marine environment.

Eating catch of the day: the diet of porbeagle shark Lamna nasus (Bonnaterre 1788) based on stomach content analysis, and the interaction with trawl fisheries in the south-western Atlantic (52° S-56° S).

This work examined the diet of the porbeagle shark Lamna nasus in the south-west Atlantic Ocean (SWAO, Argentina, 52° S-56° S) by analysing the stomach content information obtained by scientific observers who sampled specimens captured as by-catch on-board commercial fishing vessels from 2010 to 2020. A total of 148 fishing sites were analysed, in which the estimated catch was composed mainly of hoki Macruronus magellanicus (56.00%) and southern blue whiting Micromesistius australis (33.13%). From 413 porbeagle sharks sampled (292 females and 121 males) ranging from 71 to 241 cm total length (LT ) (mean: 179.76 ± 26.74 cm), 310 (75.06%) contained food in the stomachs. The forage fish were mainly hoki M. magellanicus (23.53%) and southern blue whiting M. australis (19.05%), followed by the Patagonian sprat Sprattus fuegensis (4.48%) and nototheniids (1.4%). Cephalopods and crustaceans accounted for 10% of the diet. The estimated trophic level was 4.35. Generalized linear models revealed that the consumption of hoki M. magellanicus and southern blue whiting M. australis increased with the LT of the porbeagle shark. Moreover, smaller porbeagle sharks preyed upon both small and large teleost fish, whereas larger porbeagle sharks predated exclusively upon large fish. The diet of porbeagle shark involved interactions with fisheries as it fed upon the fish species that constituted the main catch in the analysed fishing sites, as well as the main catches of the austral trawl fisheries. The ecological role of porbeagle shark observed in the SWAO exposed implications for fisheries management from a multispecies perspective.

Beyond Post-release Mortality: Inferences on Recovery Periods and Natural Mortality From Electronic Tagging Data for Discarded Lamnid Sharks

Accurately characterizing the biology of a pelagic shark species is critical when assessing its status and resilience to fishing pressure. Natural mortality (M) is well known to be a key parameter determining productivity and resilience, but also one for which estimates are most uncertain. WhileMcan be inferred from life history, validated direct estimates are extremely rare for sharks. Porbeagle (Lamna nasus) and shortfin mako (Isurus oxyrinchus) are presently overfished in the North Atlantic, but there are no directed fisheries and successful live release of bycatch is believed to have increased. UnderstandingM, post-release mortality (PRM), and variables that affect mortality are necessary for management and effective bycatch mitigation. From 177 deployments of archival satellite tags, we inferred mortality events, characterized physiological recovery periods following release, and applied survival mixture models to assessMand PRM. We also evaluated covariate effects on the duration of any recovery period and PRM to inform mitigation. Although large sample sizes involving extended monitoring periods (&amp;gt;90 days) would be optimal to directly estimateMfrom survival data, it was possible to constrain estimates and infer probable values for both species. Furthermore, the consistency ofMestimates with values derived from longevity information suggests that age determination is relatively accurate for these species. Regarding bycatch mitigation, our analyses suggest that juvenile porbeagle are more susceptible to harm during capture and handling, that keeping lamnid sharks in the water during release is optimal, and that circle hooks are associated with longer recovery periods for shortfin mako.