Publications by authors named "Thomas K Doyle"

16 Publications

  • Page 1 of 1

Distinct gelatinous zooplankton communities across a dynamic shelf sea.

Limnol Oceanogr 2019 Jul 13;64(4):1802-1818. Epub 2019 Mar 13.

The Centre for Marine and Renewable Energy Environmental Research Institute Cork Ireland.

Understanding how gelatinous zooplankton communities are structured by local hydrography and physical forcing has important implications for fisheries and higher trophic predators. Although a large body of research has described how fronts, hydrographic boundaries, and different water masses (e.g., mixed vs. stratified) influence phytoplankton and zooplankton communities, comparatively few studies have investigated their influence on gelatinous zooplankton communities. In July 2015, 49 plankton samples were collected from 50 m depth to the surface, across five transects in the Celtic Sea, of which, four crossed the Celtic Sea Front. Two distinct gelatinous communities were found in this dynamic shelf sea: a cold water community in the cooler mixed water that mainly contained neritic taxa and a warm water community in the warmer stratified water that contained a mixture of neritic and oceanic taxa. The gelatinous biomass was 40% greater in the warm water community (∼ 2 mg C m) compared with the cold water community (∼ 1.3 mg C m). The warm water community was dominated by , and , whereas the cold water community was dominated by and ctenophores. Physonect siphonophores contributed > 36% to the gelatinous biomass in the warm water community, and their widespread distribution suggests they are ecologically more important than previously thought. A distinct oceanic influence was also recorded in the wider warm water zooplankton community, accounting for a ∼ 20 mg C m increase in biomass in that region.
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http://dx.doi.org/10.1002/lno.11152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6767432PMC
July 2019

Global spatial risk assessment of sharks under the footprint of fisheries.

Authors:
Nuno Queiroz Nicolas E Humphries Ana Couto Marisa Vedor Ivo da Costa Ana M M Sequeira Gonzalo Mucientes António M Santos Francisco J Abascal Debra L Abercrombie Katya Abrantes David Acuña-Marrero André S Afonso Pedro Afonso Darrell Anders Gonzalo Araujo Randall Arauz Pascal Bach Adam Barnett Diego Bernal Michael L Berumen Sandra Bessudo Lion Natalia P A Bezerra Antonin V Blaison Barbara A Block Mark E Bond Ramón Bonfil Russell W Bradford Camrin D Braun Edward J Brooks Annabelle Brooks Judith Brown Barry D Bruce Michael E Byrne Steven E Campana Aaron B Carlisle Demian D Chapman Taylor K Chapple John Chisholm Christopher R Clarke Eric G Clua Jesse E M Cochran Estelle C Crochelet Laurent Dagorn Ryan Daly Daniel Devia Cortés Thomas K Doyle Michael Drew Clinton A J Duffy Thor Erikson Eduardo Espinoza Luciana C Ferreira Francesco Ferretti John D Filmalter G Chris Fischer Richard Fitzpatrick Jorge Fontes Fabien Forget Mark Fowler Malcolm P Francis Austin J Gallagher Enrico Gennari Simon D Goldsworthy Matthew J Gollock Jonathan R Green Johan A Gustafson Tristan L Guttridge Hector M Guzman Neil Hammerschlag Luke Harman Fábio H V Hazin Matthew Heard Alex R Hearn John C Holdsworth Bonnie J Holmes Lucy A Howey Mauricio Hoyos Robert E Hueter Nigel E Hussey Charlie Huveneers Dylan T Irion David M P Jacoby Oliver J D Jewell Ryan Johnson Lance K B Jordan Salvador J Jorgensen Warren Joyce Clare A Keating Daly James T Ketchum A Peter Klimley Alison A Kock Pieter Koen Felipe Ladino Fernanda O Lana James S E Lea Fiona Llewellyn Warrick S Lyon Anna MacDonnell Bruno C L Macena Heather Marshall Jaime D McAllister Rory McAuley Michael A Meÿer John J Morris Emily R Nelson Yannis P Papastamatiou Toby A Patterson Cesar Peñaherrera-Palma Julian G Pepperell Simon J Pierce Francois Poisson Lina Maria Quintero Andrew J Richardson Paul J Rogers Christoph A Rohner David R L Rowat Melita Samoilys Jayson M Semmens Marcus Sheaves George Shillinger Mahmood Shivji Sarika Singh Gregory B Skomal Malcolm J Smale Laurenne B Snyders German Soler Marc Soria Kilian M Stehfest John D Stevens Simon R Thorrold Mariana T Tolotti Alison Towner Paulo Travassos John P Tyminski Frederic Vandeperre Jeremy J Vaudo Yuuki Y Watanabe Sam B Weber Bradley M Wetherbee Timothy D White Sean Williams Patricia M Zárate Robert Harcourt Graeme C Hays Mark G Meekan Michele Thums Xabier Irigoien Victor M Eguiluz Carlos M Duarte Lara L Sousa Samantha J Simpson Emily J Southall David W Sims

Nature 2019 08 24;572(7770):461-466. Epub 2019 Jul 24.

Marine Biological Association of the United Kingdom, Plymouth, UK.

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.
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http://dx.doi.org/10.1038/s41586-019-1444-4DOI Listing
August 2019

Microplastic Ingestion by Gelatinous Zooplankton May Lower Efficiency of the Biological Pump.

Environ Sci Technol 2019 05 1;53(9):5387-5395. Epub 2019 Apr 1.

School of Biological, Earth and Environmental Sciences , University College Cork , Cork T23 TK30 , Ireland.

The impacts of microplastics on some individual organisms have been well studied but what is less clear is what impacts microplastics have on wider ecosystem processes. Using salps as model organisms, we studied the effect of microplastic ingestion on the downward flux of high-density particulate organic matter in the form of salp faecal pellets. While to date most microplastic studies used virgin microplastics at unrealistic environmental concentrations here we exposed Salpa fusiformis to fractured and UV exposed polyethylene and polystyrene microplastics possessing a biofilm. It was found that when exposed to environmentally relevant concentrations, reported for the Mediterranean and the South Pacific Gyre, only few faecal pellets had microplastics incorporated within them. Under potential future scenarios, however, up to 46% of faecal pellets contained microplastics. Incorporated microplastics significantly altered the size, density and sinking rates of salp faecal pellets ( p-value < 0.05 in each instance). Sinking rates decreased by 1.35-fold (95% CI = 1.18, 1.56) for faecal pellets with polyethylene microplastics and 1.47-fold (95% CI = 1.34, 1.61) for polystyrene. These results suggest that today, microplastic ingestion by salps has minimal impact on the biological pump. However, under future microplastic concentrations (or in areas such as convergent zones), microplastics may have the potential to lower the efficiency of the biological pump.
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http://dx.doi.org/10.1021/acs.est.8b07174DOI Listing
May 2019

A Paradigm Shift in the Trophic Importance of Jellyfish?

Trends Ecol Evol 2018 11 20;33(11):874-884. Epub 2018 Sep 20.

School of Biological Sciences, Queen's University Belfast, Belfast, UK.

The past 30 years have seen several paradigm shifts in our understanding of how ocean ecosystems function. Now recent technological advances add to an overwhelming body of evidence for another paradigm shift in terms of the role of gelatinous plankton (jellyfish) in marine food webs. Traditionally viewed as trophic dead ends, stable isotope analysis of predator tissues, animal-borne cameras, and DNA analysis of fecal and gut samples (metabarcoding) are all indicating that many taxa routinely consume jellyfish. Despite their low energy density, the contribution of jellyfish to the energy budgets of predators may be much greater than assumed because of rapid digestion, low capture costs, availability, and selective feeding on the more energy-rich components. Feeding on jellyfish may make marine predators susceptible to ingestion of plastics.
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http://dx.doi.org/10.1016/j.tree.2018.09.001DOI Listing
November 2018

Using tagging data and aerial surveys to incorporate availability bias in the abundance estimation of blue sharks (Prionace glauca).

PLoS One 2018 11;13(9):e0203122. Epub 2018 Sep 11.

School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland.

There is worldwide concern about the status of elasmobranchs, primarily as a result of overfishing and bycatch with subsequent ecosystem effects following the removal of top predators. Whilst abundant and wide-ranging, blue sharks (Prionace glauca) are the most heavily exploited shark species having suffered marked declines over the past decades, and there is a call for robust abundance estimates. In this study, we utilized depth data collected from two blue sharks using pop-up satellite archival tags, and modelled the proportion of time the sharks were swimming in the top 1-meter layer and could therefore be detected by observers conducting aerial surveys. The availability models indicated that the tagged sharks preferred surface waters whilst swimming over the continental shelf and during daytime, with a model-predicted average proportion of time spent at the surface of 0.633 (SD = 0.094) for on-shelf, and 0.136 (SD = 0.075) for off-shelf. These predicted values were then used to account for availability bias in abundance estimates for the species over a large area in the Northeast Atlantic, derived through distance sampling using aerial survey data collected in 2015 and 2016 and modelled with density surface models. Further, we compared abundance estimates corrected with model-predicted availability to uncorrected estimates and to estimates that incorporated the average time the sharks were available for detection. The mean abundance (number of individuals) corrected with modelled availability was 15,320 (CV = 0.28) in 2015 and 11,001 (CV = 0.27) in 2016. Depending on the year, these estimates were ~7 times higher compared to estimates without the bias correction, and ~3 times higher compared to the abundances corrected with average availability. When the survey area contains habitat heterogeneity that may affect surfacing patterns of animals, modelling animals' availability provides a robust alternative to correcting for availability bias and highlights the need for caution when applying "average" correction factors.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203122PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6133345PMC
February 2019

Evaluation of Cyanea capillata Sting Management Protocols Using Ex Vivo and In Vitro Envenomation Models.

Toxins (Basel) 2017 07 7;9(7). Epub 2017 Jul 7.

Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Mānoa, Honolulu, HI 96813, USA.

Lion's mane jellyfish () stings cause severe pain and can lead to dangerous systemic effects, including Irukandji-like syndrome. As is the case for most cnidarian stings, recommended medical protocols in response to such stings lack rigorous scientific support. In this study, we sought to evaluate potential first aid care protocols using previously described envenomation models that allow for direct measurements of venom activity. We found that seawater rinsing, the most commonly recommended method of tentacle removal for this species, induced significant increases in venom delivery, while rinsing with vinegar or Sting No More Spray did not. Post-sting temperature treatments affected sting severity, with 40 min of hot-pack treatment reducing lysis of sheep's blood (in agar plates), a direct representation of venom load, by over 90%. Ice pack treatment had no effect on sting severity. These results indicate that sting management protocols for need to be revised immediately to discontinue rinsing with seawater and include the use of heat treatment.
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http://dx.doi.org/10.3390/toxins9070215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5535162PMC
July 2017

Assessing the Efficacy of First-Aid Measures in Physalia sp. Envenomation, Using Solution- and Blood Agarose-Based Models.

Toxins (Basel) 2017 04 26;9(5). Epub 2017 Apr 26.

Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813, USA.

Stings from the hydrozoan species in the genus cause intense, immediate skin pain and elicit serious systemic effects. There has been much scientific debate about the most appropriate first aid for these stings, particularly with regard to whether vinegar use is appropriate (most current recommendations recommend against vinegar). We found that only a small percentage (≤1.0%) of tentacle cnidae discharge during a sting event using an ex vivo tissue model which elicits spontaneous stinging from live cnidarian tentacles. We then tested a variety of rinse solutions on both Atlantic and Pacific species to determine if they elicit cnidae discharge, further investigating any that did not cause immediate significant discharge to determine if they are able to inhibit cnidae discharge in response to chemical and physical stimuli. We found commercially available vinegars, as well as the recently developed Sting No More Spray, were the most effective rinse solutions, as they irreversibly inhibited cnidae discharge. However, even slight dilution of vinegar reduced its protective effects. Alcohols and folk remedies, such as urine, baking soda and shaving cream, caused varying amounts of immediate cnidae discharge and failed to inhibit further discharge, and thus likely worsen stings.
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http://dx.doi.org/10.3390/toxins9050149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5450697PMC
April 2017

Localised residency and inter-annual fidelity to coastal foraging areas may place sea bass at risk to local depletion.

Sci Rep 2017 04 4;8:45841. Epub 2017 Apr 4.

MaREI Centre, Environmental Research Institute, University College Cork, Ireland.

For many marine migratory fish, comparatively little is known about the movement of individuals rather than the population. Yet, such individual-based movement data is vitally important to understand variability in migratory strategies and fidelity to foraging locations. A case in point is the economically important European sea bass (Dicentrarchus labrax L.) that inhabits coastal waters during the summer months before migrating offshore to spawn and overwinter. Beyond this broad generalisation we have very limited information on the movements of individuals at coastal foraging grounds. We used acoustic telemetry to track the summer movements and seasonal migrations of individual sea bass in a large tidally and estuarine influenced coastal environment. We found that the vast majority of tagged sea bass displayed long-term residency (mean, 167 days) and inter-annual fidelity (93% return rate) to specific areas. We describe individual fish home ranges of 3 km or less, and while fish clearly had core resident areas, there was movement of fish between closely located receivers. The combination of inter-annual fidelity to localised foraging areas makes sea bass very susceptible to local depletion; however, the designation of protected areas for sea bass may go a long way to ensuring the sustainability of this species.
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http://dx.doi.org/10.1038/srep45841DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5379199PMC
April 2017

Enhancing public awareness and promoting co-responsibility for marine litter in Europe: The challenge of MARLISCO.

Mar Pollut Bull 2016 Jan 11;102(2):309-15. Epub 2016 Feb 11.

Mediterranean Information Office for Environment, Culture and Sustainable Development (MIO-ECSDE), 12, Kyrristou Str., 105 56 Athens, Greece. Electronic address:

Marine litter is a pervasive and complex societal problem but has no simple solution. Inadequate practices at all levels of production-use-disposal contribute to accumulation of waste on land and at sea. Enhanced societal awareness but also co-responsibility across different sectors and improved interactions between stakeholders are necessary. MARLISCO was a European initiative, which developed and implemented activities across 15 countries. It worked towards raising societal awareness and engagement on marine litter, through a combination of approaches: public exhibitions in over 80 locations; a video competition involving 2100 students; and a legacy of educational and decision-supporting tools. 12 national participatory events designed to facilitate dialogue on solutions brought together 1500 stakeholders and revealed support for cross-cutting, preventive measures. Evaluation during implementation shows that these activities are effective in improving individuals' perceptions about the problem but also commitment in being part of the solution. This paper summarises MARLISCO's approach and highlights a selection of outcomes.
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http://dx.doi.org/10.1016/j.marpolbul.2016.01.031DOI Listing
January 2016

Identification of genetically and oceanographically distinct blooms of jellyfish.

J R Soc Interface 2013 Mar 3;10(80):20120920. Epub 2013 Jan 3.

Department of Biosciences, College of Science, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, UK.

Reports of nuisance jellyfish blooms have increased worldwide during the last half-century, but the possible causes remain unclear. A persistent difficulty lies in identifying whether blooms occur owing to local or regional processes. This issue can be resolved, in part, by establishing the geographical scales of connectivity among locations, which may be addressed using genetic analyses and oceanographic modelling. We used landscape genetics and Lagrangian modelling of oceanographic dispersal to explore patterns of connectivity in the scyphozoan jellyfish Rhizostoma octopus, which occurs en masse at locations in the Irish Sea and northeastern Atlantic. We found significant genetic structure distinguishing three populations, with both consistencies and inconsistencies with prevailing physical oceanographic patterns. Our analyses identify locations where blooms occur in apparently geographically isolated populations, locations where blooms may be the source or result of migrants, and a location where blooms do not occur consistently and jellyfish are mostly immigrant. Our interdisciplinary approach thus provides a means to ascertain the geographical origins of jellyfish in outbreaks, which may have wide utility as increased international efforts investigate jellyfish blooms.
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http://dx.doi.org/10.1098/rsif.2012.0920DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565741PMC
March 2013

Pleated turtle escapes the box--shape changes in Dermochelys coriacea.

J Exp Biol 2011 Oct;214(Pt 20):3474-9

School of Biological, Earth and Environmental Sciences, University College Cork, Distillery Fields, North Mall, Cork, Ireland.

Typical chelonians have a rigid carapace and plastron that form a box-like structure that constrains several aspects of their physiology and ecology. The leatherback sea turtle, Dermochelys coriacea, has a flexible bony carapace strengthened by seven longitudinal ridges, whereas the plastron is reduced to an elliptical outer bony structure, so that the ventrum has no bony support. Measurements of the shell were made on adult female leatherbacks studied on the feeding grounds of waters off Nova Scotia (NS) and on breeding beaches of French Guiana (FG) to examine whether foraging and/or breeding turtles alter carapace size and/or shape. NS turtles exhibited greater mass and girth for a given curved carapace length (CCL) than FG turtles. Girth:CCL ratios rose during the feeding season, indicating increased girth. Measurements were made of the direct (straight) and surface (curved) distances between the medial longitudinal ridge and first right-hand longitudinal ridge (at 50% CCL). In NS turtles, the ratio of straight to curved inter-ridge distances was significantly higher than in FG turtles, indicating distension of the upper surfaces of the NS turtles between the ridges. FG females laid 11 clutches in the breeding season; although CCL and curved carapace width remained stable, girth declined between each nesting episode, indicating loss of mass. Straight to curved inter-ridge distance ratios did not change significantly during the breeding season, indicating loss of dorsal blubber before the onset of breeding. The results demonstrate substantial alterations in size and shape of female D. coriacea over periods of weeks to months in response to alterations in nutritional and reproductive status.
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http://dx.doi.org/10.1242/jeb.057182DOI Listing
October 2011

High activity and Levy searches: jellyfish can search the water column like fish.

Proc Biol Sci 2012 Feb 13;279(1728):465-73. Epub 2011 Jul 13.

Department of Biosciences, Swansea University, Singleton Park, Swansea SA2 8PP, UK.

Over-fishing may lead to a decrease in fish abundance and a proliferation of jellyfish. Active movements and prey search might be thought to provide a competitive advantage for fish, but here we use data-loggers to show that the frequently occurring coastal jellyfish (Rhizostoma octopus) does not simply passively drift to encounter prey. Jellyfish (327 days of data from 25 jellyfish with depth collected every 1 min) showed very dynamic vertical movements, with their integrated vertical movement averaging 619.2 m d(-1), more than 60 times the water depth where they were tagged. The majority of movement patterns were best approximated by exponential models describing normal random walks. However, jellyfish also showed switching behaviour from exponential patterns to patterns best fitted by a truncated Lévy distribution with exponents (mean μ=1.96, range 1.2-2.9) close to the theoretical optimum for searching for sparse prey (μopt≈2.0). Complex movements in these 'simple' animals may help jellyfish to compete effectively with fish for plankton prey, which may enhance their ability to increase in dominance in perturbed ocean systems.
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http://dx.doi.org/10.1098/rspb.2011.0978DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3234559PMC
February 2012

Gill damage to Atlantic salmon (Salmo salar) caused by the common jellyfish (Aurelia aurita) under experimental challenge.

PLoS One 2011 Apr 7;6(4):e18529. Epub 2011 Apr 7.

Coastal and Marine Research Centre, Environmental Research Institute, University College Cork, Cork, Ireland.

Background: Over recent decades jellyfish have caused fish kill events and recurrent gill problems in marine-farmed salmonids. Common jellyfish (Aurelia spp.) are among the most cosmopolitan jellyfish species in the oceans, with populations increasing in many coastal areas. The negative interaction between jellyfish and fish in aquaculture remains a poorly studied area of science. Thus, a recent fish mortality event in Ireland, involving Aurelia aurita, spurred an investigation into the effects of this jellyfish on marine-farmed salmon.

Methodology/principal Findings: To address the in vivo impact of the common jellyfish (A. aurita) on salmonids, we exposed Atlantic salmon (Salmo salar) smolts to macerated A. aurita for 10 hrs under experimental challenge. Gill tissues of control and experimental treatment groups were scored with a system that rated the damage between 0 and 21 using a range of primary and secondary parameters. Our results revealed that A. aurita rapidly and extensively damaged the gills of S. salar, with the pathogenesis of the disorder progressing even after the jellyfish were removed. After only 2 hrs of exposure, significant multi-focal damage to gill tissues was apparent. The nature and extent of the damage increased up to 48 hrs from the start of the challenge. Although the gills remained extensively damaged at 3 wks from the start of the challenge trial, shortening of the gill lamellae and organisation of the cells indicated an attempt to repair the damage suffered.

Conclusions: Our findings clearly demonstrate that A. aurita can cause severe gill problems in marine-farmed fish. With aquaculture predicted to expand worldwide and evidence suggesting that jellyfish populations are increasing in some areas, this threat to aquaculture is of rising concern as significant losses due to jellyfish could be expected to increase in the future.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0018529PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3072396PMC
April 2011

Environmental context explains Lévy and Brownian movement patterns of marine predators.

Nature 2010 Jun 9;465(7301):1066-9. Epub 2010 Jun 9.

Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK.

An optimal search theory, the so-called Lévy-flight foraging hypothesis, predicts that predators should adopt search strategies known as Lévy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey. Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Lévy behaviour has recently been questioned. Consequently, whether foragers exhibit Lévy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory's central predictions. Here we use maximum-likelihood methods to test for Lévy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Lévy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Lévy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Lévy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Lévy-flight foraging hypothesis, supporting the contention that organism search strategies naturally evolved in such a way that they exploit optimal Lévy patterns.
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http://dx.doi.org/10.1038/nature09116DOI Listing
June 2010

The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea).

J Exp Biol 2008 Aug;211(Pt 16):2566-75

School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK.

Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300-1250 m) and protracted (>1h) dives made by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed ;deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.
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http://dx.doi.org/10.1242/jeb.020065DOI Listing
August 2008

Jellyfish aggregations and leatherback turtle foraging patterns in a temperate coastal environment.

Ecology 2006 Aug;87(8):1967-72

Department of Biological Sciences, Institute of Environmental Sustainability, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, United Kingdom.

Leatherback turtles (Dermochelys coriacea) are obligate predators of gelatinous zooplankton. However, the spatial relationship between predator and prey remains poorly understood beyond sporadic and localized reports. To examine how jellyfish (Phylum Cnidaria: Orders Semaeostomeae and Rhizostomeae) might drive the broad-scale distribution of this wide ranging species, we employed aerial surveys to map jellyfish throughout a temperate coastal shelf area bordering the northeast Atlantic. Previously unknown, consistent aggregations of Rhizostoma octopus extending over tens of square kilometers were identified in distinct coastal "hotspots" during consecutive years (2003-2005). Examination of retrospective sightings data (>50 yr) suggested that 22.5% of leatherback distribution could be explained by these hotspots, with the inference that these coastal features may be sufficiently consistent in space and time to drive long-term foraging associations.
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http://dx.doi.org/10.1890/0012-9658(2006)87[1967:jaaltf]2.0.co;2DOI Listing
August 2006