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Carroll G, Abrahms B, Brodie S, Cimino MA. Spatial match-mismatch between predators and prey under climate change. Nat Ecol Evol 2024:10.1038/s41559-024-02454-0. [PMID: 38914712 DOI: 10.1038/s41559-024-02454-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 04/30/2024] [Indexed: 06/26/2024]
Abstract
Climate change is driving a rapid redistribution of life on Earth. Variability in the rates, magnitudes and directions of species' shifts can alter spatial overlap between predators and prey, with the potential to decouple trophic interactions. Although phenological mismatches between predator requirements and prey availability under climate change are well-established, 'spatial match-mismatch' dynamics remain poorly understood. We synthesize global evidence for climate-driven changes in spatial predator-prey overlap resulting from species redistribution across marine and terrestrial domains. We show that spatial mismatches can have vastly different outcomes for predator populations depending on their diet specialization and role within the wider ecosystem. We illustrate ecosystem-level consequences of climate-driven changes in spatial predator-prey overlap, from restructuring food webs to altering socio-ecological interactions. It remains unclear how predator-prey overlap at the landscape scale relates to prey encounter and consumption rates at local scales, or how the spatial reorganization of food webs affects ecosystem function. We identify key research directions necessary to resolve the scale of ecological impacts caused by species redistribution under climate change.
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Affiliation(s)
| | - Briana Abrahms
- Center for Ecosystem Sentinels, Department of Biology, University of Washington, Seattle, WA, USA
| | - Stephanie Brodie
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Environment, Brisbane, Queensland, Australia
| | - Megan A Cimino
- Institute of Marine Science, University of California Santa Cruz, Santa Cruz, CA, USA
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2
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Fahlbusch JA, Cade DE, Hazen EL, Elliott ML, Saenz BT, Goldbogen JA, Jahncke J. Submesoscale coupling of krill and whales revealed by aggregative Lagrangian coherent structures. Proc Biol Sci 2024; 291:20232461. [PMID: 38378145 PMCID: PMC10878820 DOI: 10.1098/rspb.2023.2461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 01/24/2024] [Indexed: 02/22/2024] Open
Abstract
In the marine environment, dynamic physical processes shape biological productivity and predator-prey interactions across multiple scales. Identifying pathways of physical-biological coupling is fundamental to understand the functioning of marine ecosystems yet it is challenging because the interactions are difficult to measure. We examined submesoscale (less than 100 km) surface current features using remote sensing techniques alongside ship-based surveys of krill and baleen whale distributions in the California Current System. We found that aggregative surface current features, represented by Lagrangian coherent structures (LCS) integrated over temporal scales between 2 and 10 days, were associated with increased (a) krill density (up to 2.6 times more dense), (b) baleen whale presence (up to 8.3 times more likely) and (c) subsurface seawater density (at depths up to 10 m). The link between physical oceanography, krill density and krill-predator distributions suggests that LCS are important features that drive the flux of energy and nutrients across trophic levels. Our results may help inform dynamic management strategies aimed at reducing large whales ship strikes and help assess the potential impacts of environmental change on this critical ecosystem.
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Grants
- Funding for ACCESS was provided in part by the Angell Family Foundation, Bently Foundation, Bonnell Cove Foundation, Boring Family Foundation, California Sea Grant, Elinor Patterson Baker Trust, Faucett Catalyst Fund, Firedoll Foundation, Hellman Family Foundation, Moore Family Foundation, National Fish and Wildlife Foundation, Office of National Marine Sanctuaries, Pacific Life Foundation, Resources Legacy Fund, Thelma Doelger Trust for Animals and Point Blue donors.
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Affiliation(s)
- James A. Fahlbusch
- Hopkins Marine Station, Oceans Department, Stanford University, Pacific Grove, CA, USA
- Cascadia Research Collective, Olympia, WA, USA
| | - David E. Cade
- Hopkins Marine Station, Oceans Department, Stanford University, Pacific Grove, CA, USA
| | - Elliott L. Hazen
- Hopkins Marine Station, Oceans Department, Stanford University, Pacific Grove, CA, USA
- Ecosystem Science Division, NOAA Southwest Fisheries Science Center, Monterey, CA, USA
| | - Meredith L. Elliott
- California Current Group, Point Blue Conservation Science, Petaluma, CA, USA
| | | | - Jeremy A. Goldbogen
- Hopkins Marine Station, Oceans Department, Stanford University, Pacific Grove, CA, USA
| | - Jaime Jahncke
- California Current Group, Point Blue Conservation Science, Petaluma, CA, USA
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3
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Szesciorka AR, Demer DA, Santora JA, Forney KA, Moore JE. Multiscale relationships between humpback whales and forage species hotspots within a large marine ecosystem. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2794. [PMID: 36484787 DOI: 10.1002/eap.2794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 09/22/2022] [Accepted: 09/27/2022] [Indexed: 06/17/2023]
Abstract
Fluctuations in prey abundance, composition, and distribution can impact predators, and when predators and fisheries target the same species, predators become essential to ecosystem-based management. Because of the difficulty in collecting concomitant predator-prey data at appropriate scales in patchy environments, few studies have identified strong linkages between cetaceans and prey, especially across large geographic areas. During summer 2018, a line-transect survey for cetaceans and coastal pelagic species was conducted over the continental shelf and slope of British Columbia, Canada, and the US West Coast, allowing for a large-scale investigation of predator-prey spatial relationships. We report on a case study of humpback whales (Megaptera novaeangliae) and their primary prey-Pacific herring (Clupea pallasii), northern anchovy (Engraulis mordax), and krill-using generalized additive models to explore the relationships between whale abundance on 10-km transect segments and prey metrics. Prey metrics included direct measures of biomass densities on segments and an original hotspot metric. For each prey species, segments in the upper fifth percentile for biomass density (across all segments) were designated hotspots, and whale counts on a segment were evaluated for their relationship to number of hotspot segments (species-specific and multispecies) within 25, 50, or 100 km. Whale abundance was not strongly related to direct measures of biomass densities, whereas models using hotspot metrics were more effective at describing variation in whale abundance, underscoring that evaluating prey at relevant and measurable scales is critical in patchy, dynamic marine environments. Our analysis highlighted differences in the distribution and prey availability for three humpback whale distinct population segments (DPSs) as defined under the US Endangered Species Act, including threatened and endangered DPSs that forage within the California Current Large Marine Ecosystem. These linkages provide insights into which prey species whales may be targeting in different regions and across multiple scales and, consequently, how climatic variability and anthropogenic risks may differentially impact these distinct predator-prey assemblages. By identifying scale-appropriate prey hotspots that co-occur with humpback whale aggregations, and with targeted, consistent prey sampling and estimations of potential consumption rates by whales, these findings can help inform the conservation and management of humpback whales within an ecosystem-based management framework.
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Affiliation(s)
- Angela R Szesciorka
- Environmental Assessment Services, LLC. Under Contract to NOAA Southwest Fisheries Science Center, Richland, Washington, USA
- Marine Mammal Institute, Hatfield Marine Science Center, Oregon State University, Newport, Oregon, USA
| | - David A Demer
- Fisheries Resources Division, Southwest Fisheries Science Center, NOAA, La Jolla, California, USA
| | - Jarrod A Santora
- Fisheries Ecology Division, Southwest Fisheries Science Center, NOAA, La Jolla, California, USA
- Department of Applied Math, University of California Santa Cruz, Santa Cruz, California, USA
| | - Karin A Forney
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, NOAA, Moss Landing, California, USA
- Moss Landing Marine Laboratories, San Jose State University, Moss Landing, California, USA
| | - Jeff E Moore
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, NOAA, La Jolla, California, USA
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Dey SP, Vichi M, Fearon G, Seyboth E, Findlay KP, Meynecke JO, de Bie J, Lee SB, Samanta S, Barraqueta JLM, Roychoudhury AN, Mackey B. Oceanographic anomalies coinciding with humpback whale super-group occurrences in the Southern Benguela. Sci Rep 2021; 11:20896. [PMID: 34686699 PMCID: PMC8536746 DOI: 10.1038/s41598-021-00253-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 10/07/2021] [Indexed: 11/09/2022] Open
Abstract
Seasonal feeding behaviour of humpback whales (Megaptera novaeangliae) has been observed in the coastal waters of the Southern Benguela where the species has been observed forming super-groups during the austral spring in recent years since 2011. Super-groups are unprecedented densely-packed aggregations of between 20 and 200 individuals in low-latitude waters and their occurrences indicate possible changes in feeding behaviour of the species. We accessed published data on super-groups occurrence in the study area in 2011, 2014 and 2015, and investigated oceanographic drivers that support prey availability in this region. We found that enhanced primary production is a necessary but not sufficient condition for super-groups to occur. Positive chlorophyll anomalies occurring one month prior to the super-group occurrences were identified, but only a concurrent significantly reduced water volume export from the region throughout October were conducive to the aggregations in the specific years. Hydrodynamic model results attributed the anomalous decreased volume export to the strength and orientation of the Goodhope Jet and associated eddy activity. The combination of random enhanced primary production typical of the region and emerging anomalous conditions of reduced water export in October since 2011 resulted in favourable food availability leading to the unique humpback whale aggregations. The novelty of this grouping behaviour is indicative of the lack of such oceanographic conditions in the past. Given the recency of the events, it is difficult to attribute this reduction in ocean transport to climatic regime shifts, and the origin should be likely investigated in the distant water mass interaction with the greater Agulhas system rather than in local intensifications of the upwelling conditions. A positive trend in the humpback whale population abundance points to the need to monitor the exposure of the species to the changing climate conditions.
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Affiliation(s)
- Subhra Prakash Dey
- Department of Oceanography, University of Cape Town, Rondebosch, 7701, South Africa. .,Marine and Antarctic Research Centre for Innovation and Sustainability, University of Cape Town, Rondebosch, 7701, South Africa.
| | - Marcello Vichi
- Department of Oceanography, University of Cape Town, Rondebosch, 7701, South Africa. .,Marine and Antarctic Research Centre for Innovation and Sustainability, University of Cape Town, Rondebosch, 7701, South Africa.
| | - Giles Fearon
- Department of Oceanography, University of Cape Town, Rondebosch, 7701, South Africa.,Marine and Antarctic Research Centre for Innovation and Sustainability, University of Cape Town, Rondebosch, 7701, South Africa
| | - Elisa Seyboth
- Centre for Sustainable Oceans, Faculty of Applied Sciences, Cape Peninsula University of Technology, Cape Town, South Africa
| | - Ken P Findlay
- Centre for Sustainable Oceans, Faculty of Applied Sciences, Cape Peninsula University of Technology, Cape Town, South Africa
| | - Jan-Olaf Meynecke
- Griffith Climate Change Response Program, Griffith University, Southport, Qld, Australia.,Coastal and Marine Research Centre, Griffith University, Southport, Qld, Australia
| | - Jasper de Bie
- Griffith Climate Change Response Program, Griffith University, Southport, Qld, Australia.,Coastal and Marine Research Centre, Griffith University, Southport, Qld, Australia
| | - Serena Blyth Lee
- Griffith Climate Change Response Program, Griffith University, Southport, Qld, Australia.,Coastal and Marine Research Centre, Griffith University, Southport, Qld, Australia
| | - Saumik Samanta
- Earth Sciences, Stellenbosch University, Cape Town, South Africa
| | | | | | - Brendan Mackey
- Griffith Climate Change Response Program, Griffith University, Southport, Qld, Australia
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Virgili A, Hedon L, Authier M, Calmettes B, Claridge D, Cole T, Corkeron P, Dorémus G, Dunn C, Dunn TE, Laran S, Lehodey P, Lewis M, Louzao M, Mannocci L, Martínez-Cedeira J, Monestiez P, Palka D, Pettex E, Roberts JJ, Ruiz L, Saavedra C, Santos MB, Van Canneyt O, Bonales JAV, Ridoux V. Towards a better characterisation of deep-diving whales' distributions by using prey distribution model outputs? PLoS One 2021; 16:e0255667. [PMID: 34347854 PMCID: PMC8336804 DOI: 10.1371/journal.pone.0255667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 07/21/2021] [Indexed: 11/28/2022] Open
Abstract
In habitat modelling, environmental variables are assumed to be proxies of lower trophic levels distribution and by extension, of marine top predator distributions. More proximal variables, such as potential prey fields, could refine relationships between top predator distributions and their environment. In situ data on prey distributions are not available over large spatial scales but, a numerical model, the Spatial Ecosystem And POpulation DYnamics Model (SEAPODYM), provides simulations of the biomass and production of zooplankton and six functional groups of micronekton at the global scale. Here, we explored whether generalised additive models fitted to simulated prey distribution data better predicted deep-diver densities (here beaked whales Ziphiidae and sperm whales Physeter macrocephalus) than models fitted to environmental variables. We assessed whether the combination of environmental and prey distribution data would further improve model fit by comparing their explanatory power. For both taxa, results were suggestive of a preference for habitats associated with topographic features and thermal fronts but also for habitats with an extended euphotic zone and with large prey of the lower mesopelagic layer. For beaked whales, no SEAPODYM variable was selected in the best model that combined the two types of variables, possibly because SEAPODYM does not accurately simulate the organisms on which beaked whales feed on. For sperm whales, the increase model performance was only marginal. SEAPODYM outputs were at best weakly correlated with sightings of deep-diving cetaceans, suggesting SEAPODYM may not accurately predict the prey fields of these taxa. This study was a first investigation and mostly highlighted the importance of the physiographic variables to understand mechanisms that influence the distribution of deep-diving cetaceans. A more systematic use of SEAPODYM could allow to better define the limits of its use and a development of the model that would simulate larger prey beyond 1,000 m would probably better characterise the prey of deep-diving cetaceans.
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Affiliation(s)
- Auriane Virgili
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
| | - Laura Hedon
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
| | - Matthieu Authier
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
- ADERA, Pessac Cedex, Pessac, France
| | | | - Diane Claridge
- Bahamas Marine Mammal Research Organisation, Marsh Harbour, Abaco, Bahamas
| | - Tim Cole
- Protected Species Branch, NOAA Fisheries Northeast Fisheries Science, Woods Hole, Massachusetts, United States of America
| | - Peter Corkeron
- Protected Species Branch, NOAA Fisheries Northeast Fisheries Science, Woods Hole, Massachusetts, United States of America
| | - Ghislain Dorémus
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
| | - Charlotte Dunn
- Bahamas Marine Mammal Research Organisation, Marsh Harbour, Abaco, Bahamas
| | - Tim E. Dunn
- Joint Nature Conservation Committee, Inverdee House, Aberdeen, United Kingdom
| | - Sophie Laran
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
| | | | - Mark Lewis
- Protected Species Branch, NOAA Fisheries Northeast Fisheries Science, Woods Hole, Massachusetts, United States of America
| | - Maite Louzao
- AZTI, Marine Research, Basque Research and Technology Alliance (BRTA), Pasaia, Spain
| | - Laura Mannocci
- MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
| | | | - Pascal Monestiez
- BioSP, INRA, Avignon, France
- Centre d’Etudes Biologiques de Chizé - La Rochelle, UMR 7372 CNRS—La Rochelle Université, Villiers-en-Bois, France
| | - Debra Palka
- Protected Species Branch, NOAA Fisheries Northeast Fisheries Science, Woods Hole, Massachusetts, United States of America
| | - Emeline Pettex
- ADERA, Pessac Cedex, Pessac, France
- Cohabys—ADERA, La Rochelle Université, La Rochelle, France
| | - Jason J. Roberts
- Marine Geospatial Ecology Laboratory, Duke University, Durham, North Carolina, United States of America
| | - Leire Ruiz
- AMBAR Elkartea Organisation, Bizkaia, Spain
| | - Camilo Saavedra
- Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Vigo, Spain
| | - M. Begoña Santos
- Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Vigo, Spain
| | - Olivier Van Canneyt
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
| | | | - Vincent Ridoux
- Observatoire PELAGIS, UMS 3462 CNRS—La Rochelle Université, La Rochelle, France
- Centre d’Etudes Biologiques de Chizé - La Rochelle, UMR 7372 CNRS—La Rochelle Université, Villiers-en-Bois, France
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Factors affecting the seasonal distribution and biomass of E. pacifica and T. spinifera along the Pacific coast of Canada: A spatiotemporal modelling approach. PLoS One 2021; 16:e0249818. [PMID: 33989288 PMCID: PMC8121349 DOI: 10.1371/journal.pone.0249818] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 03/26/2021] [Indexed: 11/19/2022] Open
Abstract
Euphausiids are a keystone species in coastal food webs due to their high lipid content and seasonally high biomass. Understanding the habitat and environmental drivers that lead to areas of high biomass, or ‘hotspots’, and their seasonal persistence, will support the identification of important foraging regions for mid- and upper- trophic level predators. We quantify the distribution of hotspots of the two dominant species of euphausiid in the north-east Pacific Ocean: Euphausia pacifica and Thysanoessa spinifera, as well as euphausiid larvae (mixed species). The Canadian coast encompasses the northern California Current Ecosystem and the transition zone to the Alaska current, and is a highly productive region for fisheries, marine mammals, and seabirds. We used spatiotemporal modelling to predict the distribution of these three euphausiid groups in relation to geomorphic and environmental variables during the important spring-summer months (April through September) when euphausiid biomass is highest. We quantified the area, intensity, and persistence of biomass hotspots across months according to specific oceanographic ecosections developed for marine spatial planning purposes. Persistent hotspots of both adult species were predicted to occur along the 200 m depth contour of the continental slope; however, differences were predicted on the shallower Dixon shelf, which was a key area for T. spinifera, and within the Juan de Fuca Eddy system where E. pacifica hotspots occurred. The continental slope along the west coast of Vancouver Island was the only persistent hotspot region common between both adult species and euphausiid larvae. Larval distribution was more correlated with T. spinifera than E. pacifica biomass. Hotspots of adults were more persistent across months than hotspots of euphausiid larvae, which were seasonally patchy. The persistence of biomass hotspots of forage species through periods of low overall biomass could maintain trophic connectivity through perturbation events and increase ecosystem resilience to climate change.
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Bedriñana-Romano L, Hucke-Gaete R, Viddi FA, Johnson D, Zerbini AN, Morales J, Mate B, Palacios DM. Defining priority areas for blue whale conservation and investigating overlap with vessel traffic in Chilean Patagonia, using a fast-fitting movement model. Sci Rep 2021; 11:2709. [PMID: 33526800 PMCID: PMC7851173 DOI: 10.1038/s41598-021-82220-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 12/18/2020] [Indexed: 01/30/2023] Open
Abstract
Defining priority areas and risk evaluation is of utmost relevance for endangered species` conservation. For the blue whale (Balaenoptera musculus), we aim to assess environmental habitat selection drivers, priority areas for conservation and overlap with vessel traffic off northern Chilean Patagonia (NCP). For this, we implemented a single-step continuous-time correlated-random-walk model which accommodates observational error and movement parameters variation in relation to oceanographic variables. Spatially explicit predictions of whales' behavioral responses were combined with density predictions from previous species distribution models (SDM) and vessel tracking data to estimate the relative probability of vessels encountering whales and identifying areas where interaction is likely to occur. These estimations were conducted independently for the aquaculture, transport, artisanal fishery, and industrial fishery fleets operating in NCP. Blue whale movement patterns strongly agreed with SDM results, reinforcing our knowledge regarding oceanographic habitat selection drivers. By combining movement and density modeling approaches we provide a stronger support for purported priority areas for blue whale conservation and how they overlap with the main vessel traffic corridor in the NCP. The aquaculture fleet was one order of magnitude larger than any other fleet, indicating it could play a decisive role in modulating potential negative vessel-whale interactions within NCP.
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Affiliation(s)
- Luis Bedriñana-Romano
- grid.7119.e0000 0004 0487 459XInstituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile ,NGO Centro Ballena Azul, Valdivia, Chile
| | - Rodrigo Hucke-Gaete
- grid.7119.e0000 0004 0487 459XInstituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile ,NGO Centro Ballena Azul, Valdivia, Chile
| | - Francisco A. Viddi
- grid.7119.e0000 0004 0487 459XInstituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile ,NGO Centro Ballena Azul, Valdivia, Chile
| | - Devin Johnson
- Marine Mammal Laboratory, Alaska Fisheries Science Center/NOAA, 7600 Sand Point Way NE, Seattle, WA USA
| | - Alexandre N. Zerbini
- Marine Mammal Laboratory, Alaska Fisheries Science Center/NOAA, 7600 Sand Point Way NE, Seattle, WA USA ,grid.508396.1Marine Ecology and Telemetry Research, 2468 Camp McKenzie Tr NW, Seabeck, WA 98380 USA ,grid.448402.e0000 0004 5929 5632Cascadia Research Collective, 218 ½ 4th Ave, Olympia, WA 98502 USA ,Instituto Aqualie, Av. Dr. Paulo Japiassú Coelho, 714, Sala 206, Juiz de Fora, MG 36033-310 Brazil
| | - Juan Morales
- grid.412234.20000 0001 2112 473XGrupo de Ecología Cuantitativa, INIBIOMA-CONICET, Universidad Nacional del Comahue, Bariloche, Argentina
| | - Bruce Mate
- grid.4391.f0000 0001 2112 1969Marine Mammal Institute and Department of Fisheries and Wildlife, Hatfield Marine Science Center, Oregon State University, Newport, OR USA
| | - Daniel M. Palacios
- grid.4391.f0000 0001 2112 1969Marine Mammal Institute and Department of Fisheries and Wildlife, Hatfield Marine Science Center, Oregon State University, Newport, OR USA
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Rockwood RC, Adams J, Silber G, Jahncke J. Estimating effectiveness of speed reduction measures for decreasing whale-strike mortality in a high-risk region. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01056] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Recent estimates of blue (Balaenoptera musculus) and humpback (Megaptera novaeangliae) whale ship-strike deaths on the US west coast are above the Potential Biological Removal limit determined by the National Marine Fisheries Service. Beginning in 2015, the National Oceanographic and Atmospheric Administration requested voluntary Vessel Speed Reductions (VSR) in the designated shipping routes off San Francisco, California, USA, in order to decrease whale mortality from ship strikes. We applied a ship strike model based on whale density and Automatic Identification System (AIS) vessel data. We bootstrapped speeds from vessels that transited when no VSR was in place to assess the effect of the VSR on strike mortality rates. Finally, we calculated the expected mortality for hypothetical compliance scenarios by programmatically imposing speed caps. Average predicted mortality for the region was 2.7 blue whales and 7.0 humpback whales in a 4 month period. Compared to years prior to the VSR (2012-2014), vessel speeds during the VSR were slower. This lowered blue whale deaths within the shipping lanes by 11-13% and humpback whale deaths by 9-10% in 2016-2017. If 95% of mariners adhered to recommended 10 knot (kn) limits in the shipping lanes alone, we predicted twice as many blue whale and 3 times as many humpback whale deaths would be avoided relative to current adherence. Adding a 10 kn speed limit (with 95% cooperation) at the ends of each of the lanes would result in about 5- and 4-fold reductions in blue whale and humpback whale mortality, respectively, relative to current practices. Our approach can evaluate ship strikes and mitigation measures for whale populations around the globe.
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Affiliation(s)
- RC Rockwood
- Point Blue Conservation Science, Petaluma, California 94954, USA
| | - J Adams
- National Marine Fisheries Service, Office of Protected Resources, Silver Springs, Maryland 20910, USA
| | - G Silber
- Smultea Environmental Sciences, Washington Grove, Maryland 20880, USA
| | - J Jahncke
- Point Blue Conservation Science, Petaluma, California 94954, USA
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