Browsing by Author "Carlson, John"
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- Age and growth of shortfin mako in the South AtlanticPublication . Rosa, Daniela; Mas, Federico; Mathers, Alyssa; Natanson, Lisa J.; Carlson, John; Coelho, RuiThe 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.
- Blue shark (Prionace glauca) movements, habitat use, and vertical overlap with longline fishing gears in the southwestern Atlantic OceanPublication . Mas, Federico; Cortés, Enric; Coelho, Rui; Defeo, Omar; Miller, Philip; Carlson, John; Gulak, Simon; Domingo, AndrésOver the last three decades, the advent and the continuous sophistication of telemetry devices have revolutionized our understanding of how pelagic sharks move and exploit their three-dimensional underwater habitat, with implications for management and conservation. In this study, conventional (4,648) and electronic (18) tags were used to assess the horizontal and vertical movements of blue sharks, Prionace glauca, and their vertical overlap with shallow and deep-set longline fishing gears in the southwestern Atlantic Ocean. Results revealed prolonged permanence in the area, large-scale displacements, including trans-equatorial, trans-Atlantic and Indian-Atlantic movements, and high daily displacement rates. Blue sharks showed an extensive use of the water column and considerable variability among and within individuals in vertical behavior, involving normal and reverse diel vertical migrations, surface-oriented behavior, extended use of mesopelagic waters, and occasional extreme dives into bathypelagic waters. Depth distribution appeared unrelated to size or sex but was influenced by the time of day and temperature, with deeper and colder temperatures consistently found during the day. The moon cycle affected the vertical distribution of some sharks but not others. Temperature-depth recorders deployed on hooks, combined with depth distribution from electronic tags, provided insightful information on the species' vertical overlap with shallow- and deep-set longline configurations. Encounterability values were higher during nighttime and lower during daytime for both longline configurations, but were largely affected by the individuals' vertical behavior, highlighting the importance of accounting for environmental conditions besides fishing gear configuration and metiers. This novel information on blue sharks' movements and fishery interactions in the South Atlantic Ocean can inform future management and conservation strategies.
- Habitat use and migrations of shortfin mako in the atlantic using satellite telemetryPublication . Santos, Catarina C.; Domingo, Andrés; Carlson, John; Natanson, Lisa J.; Cortés, Enric; Miller, Philip; Hazin, Fábio H. V.; Travassos, Paulo; Mas, Federico; Coelho, RuiThis paper provides an update of the study on habitat use for shortfin mako, developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Currently, all phase 1 (2015-2016) tags (23 tags: 9 miniPATs and 14 sPAT) and 11 tags from phase 2 (2016-2018) have been deployed by observers on Portuguese, Uruguayan, Brazilian and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 32 tags/specimens is available and a total of 1260 tracking days have been recorded. Results showed shortfin makos moved in multiple directions, travelling considerable distances. Shortfin mako sharks spent most of their time above the thermocline (0-90 m), between 18 and 22 °C. The main plan for the next phase of the project is to continue the tag deployment during 2018 in several regions of the Atlantic.
- Movements, habitat use, and diving behavior of Shortfin Mako in the Atlantic OceanPublication . Casaca Santos, Catarina; Domingo, Andrés; Carlson, John; Natanson, Lisa J.; Travassos, Paulo; Macías, David; Cortés, Enric; Miller, Philip; Hazin, Fábio; Mas, Federico; Ortiz de Urbina, Josetxu; Lino, Pedro G.; Coelho, RuiThe shortfin mako is one of the most important shark species caught in Atlantic Ocean pelagic fisheries. Given increasing concerns for the stock status of the species, the present study was designed to fill gaps in the knowledge of habitat use and movement patterns of shortfin mako in the Atlantic Ocean. From 2015 to 2019, 53 shortfin makos were tagged with pop-up satellite archival tags within the North, Central, and Southwest Atlantic Ocean, with successful transmissions received from 34 tags. Generally, sharks tagged in the Northwest and Central Atlantic moved away from tagging sites showing low to no apparent residency patterns, whereas sharks tagged in the Northeast and Southwest Atlantic spent large periods of time near the Canary Archipelago and Northwest Africa, and over shelf and oceanic waters off southern Brazil and Uruguay, respectively. These areas showed evidence of site fidelity and were identified as possible key areas for shortfin mako. Sharks spent most of their time in temperate waters (18–22◦C) above 90 m; however, data indicated the depth range extended from the surface down to 979 m, in water temperatures ranging between 7.4 and 29.9◦C. Vertical behavior of sharks seemed to be influenced by oceanographic features, and ranged from marked diel vertical movements, characterized by shallower mean depths during the night, to yo-yo diving behavior with no clear diel pattern observed. These results may aid in the development of more informed and efficient management measures for this species.
- Post-release mortality of shortfin mako in the Atlantic using satellite telemetry: preliminary resultsPublication . Domingo, Andrés; Casaca Santos, Catarina; Carlson, John; Natanson, Lisa; Cortés, Enric; Mas, Federico; Miller, Philip; Hazin, Fábio H. V.; Travassos, Paulo; Coelho, RuiThis 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.
- Progress report for SRDCP on the Atlantic-wide study on the age and growth of shortfin mako sharkPublication . Rosa, Daniela; Mas, Federico; Mathers, Alyssa; Natanson, Lisa J.; Domingo, Andrés; Carlson, John; Coelho, RuiThe 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.
- Satellite tagging of shortfin mako for habitat use and post-release survival: progress report for SRDCPPublication . Coelho, Rui; Domingo, Andrés; Carlson, John; Natanson, Lisa; Cortés, Enric; Miller, PhilipThis 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.
- Shark research and data collection program : progress on the age and growth of the shortfin mako in the Atlantic OceanPublication . Coelho, Rui; Carlson, John; Natanson, Lisa; Rosa, Daniela; Mas, Federico; Mathers, Alyssa; Domingo, Andrés; Santos, MiguelThis paper presents an update of the age and growth study within the ICCAT Shark Research and Data Collection Program (SRDCP), including the current development status and plans for the 2nd phase of the project. There are currently 469 vertebrae samples (205 females, 257 males and 7 specimens with unidentified sex) collected and processed from both the North and Southern hemispheres. The sample distribution is much more complete in the north, while in the south at this stage there are only samples from the equatorial region. The size range of the samples varies from 52 cm to 366 cm FL. The next steps of this projects is proposing a workshop on age reading and growth in order to prepare a reference set of vertebrae that can be used as a guideline for the readings of the remaining sample, and also discuss aspects of age validation and band deposition periodicity. The final results will be presented to the SCRS sharks working group in 2017, in order to contribute to the 2017 shortfin mako stock assessment.
- Shark Research and Data Collection Program: progress on the age and growth of the shortfin mako in the Atlantic OceanPublication . Coelho, Rui; Carlson, John; Natanson, Lisa; Rosa, Daniela; Mas, Federico; Mathers, Alyssa; Domingo, Andrés; Santos, Miguel N.This paper presents an update of the age and growth study within the ICCAT Shark Research and Data Collection Program (SRDCP), including the current development status and plans for the 2nd phase of the project. There are currently 469 vertebrae samples (205 females, 257 males and 7 specimens with unidentified sex) collected and processed from both the North and Southern hemispheres. The sample distribution is much more complete in the north, while in the south at this stage there are only samples from the equatorial region. The size range of the samples varies from 52 cm to 366 cm FL. The next steps of this projects is proposing a workshop on age reading and growth in order to prepare a reference set of vertebrae that can be used as a guideline for the readings of the remaining sample, and also discuss aspects of age validation and band deposition periodicity. The final results will be presented to the SCRS sharks working group in 2017, in order to contribute to the 2017 shortfin mako stock assessment.
- Shark Research and Data Collection Program: progress on the satellite tagging of shortfin mako for post-release survival and habitat use studiesPublication . Coelho, Rui; Domingo, Andrés; Carlson, John; Cortés, Enric; Rosa, Daniela; ller, Philip; Santos, Miguel N.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 other on post-release survival. At the time of this paper, 10 tags (6 miniPATs and 4 sPAT) had been deployed from observers on Portuguese fishing vessels in the temperate NE Atlantic. The remaining tags are being deployed by USA in the temperate NW and Uruguay in the SW. The preliminary analysis shows that specimens tagged in the temperate NE moved to southern areas, while specimens tagged in the tropical NE close to the Cabo Verde archipelago moved easterly to the African continent. Three tags were deployed in equatorial waters and one moved to the NE while the other moved SE. In terms of post-release survivorship, 2 specimens tagged with sPATs survived and 2 died. For the 2nd year of the project we will acquire additional miniPATs to be deployed preferably in equatorial waters, in the mixing zone for the stocks.