Bomb radiocarbon and tag-recapture dating of sandbar shark (Carcharhinus plumbeus)

The sandbar shark (Carcharhinus plumbeus) was the cornerstone species of western North Atlantic and Gulf of Mexico large coastal shark fisheries until 2008 when they were allocated to a research-only fishery. Despite decades of fishing on this species, important life history parameters, such as age and growth, have not been well known. Some validated age and growth information exists for sandbar shark, but more comprehensive life history information is needed. The complementary application of bomb radiocarbon and tag-recapture dating was used in this study to determine valid age-estimation criteria and longevity estimates for this species. These two methods indicated that current age interpretations based on counts of growth bands in vertebrae are accurate to 10 or 12 years. Beyond these years, we could not determine with certainty when such an underestimation of age begins; however, bomb radiocarbon and tag-recapture data indicated that large adult sharks were considerably older than the estimates derived from counts of growth bands. Three adult sandbar sharks were 20 to 26 years old based on bomb radiocarbon results and were a 5- to 11-year increase over the previous age estimates for these sharks. In support of these findings, the tag-recapture data provided results that were consistent with bomb radiocarbon dating and further supported a longevity that exceeds 30 years for this species

Progress report for SRDCP on the Atlantic-wide study on the age and growth of shortfin mako shark

The ICCAT Shark Research and Data Collection Program (SRDCP) aims to develop and coordinate science and science-related activities needed to support provision of sound scientific advice for the conservation and management of pelagic sharks in the Atlantic. This Program was developed in 2013-2014 by the Sharks Species Group, and framed within the 2015-2020 SCRS Strategic Plan. Within this Program, a specific study on the age and growth of shortfin mako in the Atlantic was developed, with the purpose of contributing to the 2017 ICCAT SMA stock assessment. In the paper, we provide an update of the project, including preliminary growth models for the North Atlantic Ocean.Project "LL-Sharks: Mitigação das capturas de tubarões na pescaria de palangre de superfície (Ref: 31-03-05-FEP-44, funded by PROMAR)", Project "MAKO-WIDE - "A wide scale inter-hemispheric and inter-disciplinary study aiming the conservation of the shortfin mako shark in the Atlantic Ocean (Ref: FAPESP/19740/2014)", funded by FCT (Portuguese Foundation for Science and Technology) and FAPESP (São Paulo Research Foundation, Brazil), and Project SAFEWATERS SC7 (The provision of advice on the conservation of pelagic sharks associated to fishing activity under EU Sustainable Fisheries Partnership Agreements in the Atlantic Ocean) under the Framework Contract MARE/2012/21, funded by the European Commission. Additional satellite tags were acquired by NOAA in US-Uruguay and US-Portugal-Uruguay collaboration initiatives. Rui Coelho is supported by an Investigador-FCT contract from the Portuguese Foundation for Science and Technology (FCT) supported by the EU European Social Fund and the Programa Operacional Potencial Humano (Ref: IF/00253/2014). Catarina C. Santos is supported by an FCT Doctoral grant (Ref: SFRH/BD/139187/2018).info:eu-repo/semantics/draf

Inferring Life History Characteristics of the Oceanic Whitetip Shark \u3cem\u3eCarcharhinus longimanus\u3c/em\u3e From Vertebral Bomb Radiocarbon

Oceanic whitetip sharks Carcharhinus longimanus are a cosmopolitan epipelagic species that was once prolific throughout the tropics and subtropics but was recently listed as Critically Endangered by the International Union for the Conservation of Nature and as Threatened under the United States Endangered Species Act. Although historically conspicuous in oceanic fisheries catches, relatively little is known about their habitat use, movement, and life history during migration. Given the paucity of data on migratory patterns and lack of age estimate validation available for this species, we evaluated vertebral growth bands for bomb radiocarbon (14C) patterns to derive additional information on these metrics. Individual growth bands (n = 62) were milled from vertebrae of eight individuals caught in the northwestern Atlantic Ocean. Age estimates based on vertebral growth bands ranged 1–13 years, with capture dates spanning 1978–2004. Plots of vertebral Δ14C relative to regional coral, shark, and fish otolith reference curves suggest age estimates based on presumed annual growth bands were accurate, although specimens were not old enough to capture the most informative portion of the bomb radiocarbon reference period. The magnitude of Δ14C varied among individuals, and individual chronologies demonstrated semi-cyclic patterns of Δ14C depletion and subsequent enrichment, which may be indicative of changes to diet as a function of annual migratory patterns and is supported by recently published telemetry, diet, and stable isotope studies. Although these data are preliminary in nature, they provide some evidence that Δ14C patterns in vertebrae can serve as a multi-purpose tool for life history studies of oceanic sharks

Satellite tagging of shortfin mako for habitat use and post-release survival: progress report for SRDCP

This paper provides an update of two projects developed within the ICCAT Shark Research and Data Collection Program (SRDCP) using satellite telemetry, specifically a study on habitat use and another on post-release survival. Currently, all phase 1 (2015-2016) tags (23 tags: 9 miniPATs and 14 sPAT) have been deployed by observers on Portuguese, Uruguayan and US vessels in the temperate NE, temperate NW and SW Atlantic. A total of 668 tracking days have been recorded. In terms of post-release survivorship, data from 19 tags/specimens is available. From those, 6 specimens died (31.6%) while the remaining 13 (68.4%) survived the first 30 days after tagging. All planned project milestones and deliverables have been achieved and delivered in due time. For the 2nd phase of the project (2016-2017) 12 miniPATS were acquired and will be deployed during 2017 in various regions of the Atlantic, including temperate, tropical and equatorial waters.info:eu-repo/semantics/publishedVersio

Post-release mortality of shortfin mako in the Atlantic using satellite telemetry: preliminary results

This paper provides an update of the study on post-release mortality of the shortfin mako, Isurus oxyrinchus developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Up to date, 34 tags (14 sPATs and 20 miniPATs) have been deployed by observers on Brazilian, Portuguese, Uruguayan, and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 28 out of 34 tagged specimens could be used to obtain preliminary information regarding post-release mortality, resulting in a total of 7 mortality and 21 survival events.This study was carried out as part of a cooperative work conducted by the ICCAT Shark species group integrated in the ICCAT Shark Research and Data Collection Program (SRDCP). The authors are grateful to all fishery observers and longline skippers from the Nations involved in this study. Tags from additional sources have been contributed and deployed with several national Projects, specifically: Project "LL-Sharks: Mitigação das capturas de tubarões na pescaria de palangre de superfície (Ref: 31-03-05-FEP-44, funded by PROMAR)", Project "MAKO-WIDE - "A wide scale inter-hemispheric and inter-disciplinary study aiming the conservation of the shortfin mako shark in the Atlantic Ocean (Ref: FAPESP/19740/2014)", funded by FCT (Portuguese Foundation for Science and Technology) and FAPESP (São Paulo Research Foundation, Brazil), and Project SAFEWATERS SC7 (The provision of advice on the conservation of pelagic sharks associated to fishing activity under EU Sustainable Fisheries Partnership Agreements in the Atlantic Ocean) under the Framework Contract MARE/2012/21, funded by the European Commission. Additional satellite tags were acquired by NOAA in US-Uruguay and US-Portugal-Uruguay collaboration initiatives. Rui Coelho is supported by an Investigador-FCT contract from the Portuguese Foundation for Science and Technology (FCT) supported by the EU European Social Fund and the Programa Operacional Potencial Humano (Ref: IF/00253/2014).info:eu-repo/semantics/draf

Age and growth of shortfin mako in the South Atlantic

The shortfin mako, Isurus oxyrinchus (Lamnidae), is regularly caught as by-catch in pelagic longline fisheries and is among the most vulnerable sharks to this fishery. The age and growth of I. oxyrinchus was studied along a wide South Atlantic region. Data from 332 specimens ranging in size from 90 to 330 cm fork length (FL) for females and 81 to 250 cm FL for males were analysed. Growth models were fitted using the von Bertalanffy growth equation re-parameterised to calculate L0, instead of t0, and a modification of this equation using the known size at birth. The von Bertalanffy growth equation with fixed L0 (size at birth = 63 cm FL) with resulting growth parameters of Linf = 218.5 cm FL, k = 0.170 year-1 for males and Linf = 263.1 cm FL, k = 0.112 year-1 for females, seemed to underestimate maximum length for this species, while overestimating k. Given the poorly estimated parameters we cannot, to this point, recommend the use of the South Atlantic growth curves.info:eu-repo/semantics/publishedVersio

Updated reproductive parameters for the shortfin mako (Isurus oxyrinchus) in the North Atlantic Ocean with inferences of distribution by sex and reproductive stage

Prompted by recent concern about the stock status of the shortfin mako (Isurus oxyrinchus) in the North Atlantic Ocean, we examined reproductive data from 731 individuals (351 females and 380 males) collected by 3 scientific organizations to improve estimates of size and age at maturity. Males ranged in size from 70 to 283 cm fork length (FL) and females from 71 to 338 cm FL. Females matured between 263 and 291 cm FL, with an estimated median length at maturity (L50) of 280 cm FL and a median weight at maturity (WT50) of 275 kg. Males matured between 173 and 187 cm FL, with an L50 of 182 cm FL and WT50 of 64 kg. Catch records from 4 international programs were also examined to investigate spatiotemporal variation in the distribution of life history stages based on updated size-at-maturity estimates and to identify potential parturition and nursery grounds. These records identified the Gulf of Mexico and the eastern North Atlantic Ocean off Portugal as birthing and nursery areas, with the most important nursery area occurring in the western North Atlantic Ocean.FCT MAKO-WIDE (Ref. FAPESP/19740/2014)info:eu-repo/semantics/publishedVersio

The reproductive biology of the porbeage shark (Lamna nasus) in the western North Atlantic Ocean

Reproductive organs from 393 male and 382 female porbeagles (Lamna nasus), caught in the western North Atlantic Ocean, were examined to determine size at maturity and reproductive cycle. Males ranged in size from 86 to 246 cm fork length (FL) and females ranged from 94 to 288 cm FL. Maturity in males was best described by an inflection in the relationship of clasper length to fork length when combined with clasper calcification. Males matured between 162 and 185 cm FL and 50% were mature at 174 cm FL. In females, all reproductive organ measurements related to body length showed a strong inflection around the size of maturity. Females matured between 210 and 230 cm FL and 50% were mature at 218 cm FL. After a protracted fall mating period (September–November), females give birth to an average of 4.0 young in spring (April−June). As in other lamnids, young are nourished through oophagy. Evidence from this study indicated a one-year reproductive cycle and gestation period lasting 8–9 months

Horizontal and vertical movement patterns and habitat use of juvenile porbeagles (Lamna nasus) in the Western North Atlantic

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Skomal, G., Marshall, H., Galuardi, B., Natanson, L., Braun, C. D., & Bernal, D. Horizontal and vertical movement patterns and habitat use of juvenile porbeagles (Lamna nasus) in the Western North Atlantic. Frontiers in Marine Science, 8,(2021): 624158, https://doi.org/10.3389/fmars.2021.624158.The porbeagle (Lamna nasus) is a large, highly migratory endothermic shark broadly distributed in the higher latitudes of the Atlantic, South Pacific, and Indian Oceans. In the North Atlantic, the porbeagle has a long history of fisheries exploitation and current assessments indicate that this stock is severely overfished. Although much is known of the life history of this species, there is little fisheries-independent information about habitat preferences and ecology. To examine migratory routes, vertical behavior, and environmental associations in the western North Atlantic, we deployed pop-up satellite archival transmitting tags on 20 porbeagles in late November, 2006. The sharks, ten males and ten females ranging from 128 to 154 cm fork length, were tagged and released from a commercial longline fishing vessel on the northwestern edge of Georges Bank, about 150 km east of Cape Cod, MA. The tags were programmed to release in March (n = 7), July (n = 7), and November (n = 6) of 2007, and 17 (85%) successfully reported. Based on known and derived geopositions, the porbeagles exhibited broad seasonally-dependent horizontal and vertical movements ranging from minimum linear distances of 937 to 3,310 km and from the surface to 1,300 m, respectively. All of the sharks remained in the western North Atlantic from the Gulf of Maine, the Scotian Shelf, on George's Bank, and in the deep, oceanic waters off the continental shelf along the edge of, and within, the Gulf Stream. In general, the population appears to be shelf-oriented during the summer and early fall with more expansive offshore radiation in the winter and spring. Although sharks moved through temperatures ranging from 2 to 26°C, the bulk of their time (97%) was spent in 6-20°C. In the summer months, most of the sharks were associated with the continental shelf moving between the surface and the bottom and remaining < 200 m deep. In the late fall and winter months, the porbeagles moved into pelagic habitat and exhibited two behavioral patterns linked with the thermal features of the Gulf Stream: “non-divers” (n = 7) largely remained at epipelagic depths and “divers” (n = 10) made frequent dives into and remained at mesopelagic depths (200–1000 m). These data demonstrate that juvenile porbeagles are physiologically capable of exploiting the cool temperate waters of the western North Atlantic as well as the mesopelagic depths of the Gulf Stream, possibly allowing exploitation of prey not available to other predators.This research was funded by the Large Pelagics Research Center (Grant 06-125)

Updates on post-release mortality of shortfin mako in the Atlantic using satellite telemetry

This paper provides an update of the study on post-release mortality of the shortfin mako, Isurus oxyrinchus developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Up to date, 43 tags (14 sPATs and 29 miniPATs) have been deployed by observers on Brazilian, Portuguese, Spanish, Uruguayan, and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 35 out of 43 tagged specimens could be used to obtain preliminary information regarding post-release mortality, resulting in a total of 8 mortality and 27 survival events.This study was carried out as part of a cooperative work conducted by the ICCAT Shark species group integrated in the ICCAT Shark Research and Data Collection Program (SRDCP). The authors are grateful to all fishery observers and longline skippers from the Nations involved in this study. Tags from additional sources have been contributed and deployed with several national Projects, specifically: Project "LL-Sharks: Mitigação das capturas de tubarões na pescaria de palangre de superfície (Ref: 31-03-05-FEP-44, funded by PROMAR)", Project "MAKO-WIDE - "A wide scale inter-hemispheric and inter-disciplinary study aiming the conservation of the shortfin mako shark in the Atlantic Ocean (Ref: FAPESP/19740/2014)", funded by FCT (Portuguese Foundation for Science and Technology) and FAPESP (São Paulo Research Foundation, Brazil), and Project SAFEWATERS SC7 (The provision of advice on the conservation of pelagic sharks associated to fishing activity under EU Sustainable Fisheries Partnership Agreements in the Atlantic Ocean) under the Framework Contract MARE/2012/21, funded by the European Commission. Additional satellite tags were acquired by NOAA in US-Uruguay and US-Portugal-Uruguay collaboration initiatives. Rui Coelho is supported by an Investigador-FCT contract from the Portuguese Foundation for Science and Technology (FCT) supported by the EU European Social Fund and the Programa Operacional Potencial Humano (Ref: IF/00253/2014). Catarina C. Santos is supported by an FCT Doctoral grant (Ref: SFRH/BD/139187/2018).info:eu-repo/semantics/draf