Sea-surface temperature gradients across blue whale and sea turtle foraging trajectories off the Baja California Peninsula, Mexico

Etnoyer, Peter J.; Canny, David; Mate, Bruce R.; Morgan, Lance E.; Ortega‐Ortiz, Joel G.; Nichols, Wallace J.

doi:10.1016/j.dsr2.2006.01.010

Cited by 96 publications

(81 citation statements)

References 40 publications

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“…Therefore, loggerhead turtle movements may comprise a combination of active station holding and passive current-driven drifting (Cardona et al 2005, Hays et al 2010. Studies off the Baja California Peninsula indicate that juvenile loggerhead turtles may take up residency for extended periods before returning to the western Pacific Ocean (Nichols et al 2000, Seminoff et al 2004, Etnoyer et al 2006. Our findings suggest that a similar scenario occurs in the waters off Peru and northern Chile.…”

Section: Environmental Factorssupporting

confidence: 50%

Post-capture movements of loggerhead turtles in the southeastern Pacific Ocean assessed by satellite tracking

Mangel

Alfaro‐Shigueto²,

Witt³

et al. 2011

Mar. Ecol. Prog. Ser.

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The post-capture movements made by loggerhead sea turtles Caretta caretta in the southeastern Pacific Ocean were monitored from 2003 to 2007. Fourteen loggerhead turtles were fitted with satellite transmitters and released off the coast of Peru. All turtles were juveniles (curved carapace length range: 40.5 to 68.5 cm) incidentally captured by small-scale longline fishing vessels from southern or central Peru. Track durations were highly variable (mean ± SD: 143 ± 90 d; range: 8 to 297 d) with no clear signs of immediate post-release mortality. Upon release, all turtles moved offshore beyond the continental shelf. Eight of 11 turtles tracked for > 60 d had final displacements of < 750 km, suggesting that loggerhead turtles often maintain extended residency in these waters and that this area is an important foraging zone for loggerhead turtles of southwest Pacific origin. Satellite tracks also showed a substantial overlap of areas used by turtles with known Peruvian longline fishing effort. Turtles spent 75% of their time within the area fished by this fleet (based upon observed sets). This suggests that turtles are vulnerable to fishery interactions and that bycatch mitigation measures should be employed to minimize fishery impacts on loggerhead turtles. The loggerhead turtles tracked during this study spent ca. 51% of their time in Peruvian waters, 39% in international waters and 9% in Chilean waters, which emphasizes the need for a multinational approach to sea turtle conservation and fisheries management in the region.KEY WORDS: Caretta caretta · Peru · Chile · Small-scale fisheries · Bycatch · Habitat · Governance Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 433: [261][262][263][264][265][266][267][268][269][270][271][272] 2011 been linked through genetic analyses and satellite tracking to aggregations of juveniles and subadults found in the central and eastern Pacific (Bowen 1995, Nichols et al. 2000, Polovina et al. 2006, Howell et al. 2010. In the South Pacific Ocean, decades of intense monitoring in eastern Australia has helped in defining many aspects of the nesting and oceanic ecology of loggerhead turtles in the western South Pacific region and in describing declining trends in abundance of that population (Limpus & Limpus 2003a). However, it was not until 2004 that the species was confirmed in the southeastern Pacific Ocean (SEP) through a combination of onboard and shore-based fisheries monitoring (Alfaro-Shigueto et al. 2004). Genetic studies have shown that the juvenile loggerhead turtles found in the SEP originate from Australian and New Caledonian rookeries (Alfaro-Shigueto et al. 2004, Boyle et al. 2009). Additional reports now also confirm the occurrence of loggerhead turtles off Ecuador and Columbia (Alava 2008) and Chile to a latitude of 32° S (Donoso & Dutton 2010). Alfaro-Shigueto et al. (2008) report primarily small-to medium-sized juveniles and subadultsized turtles found off the Peruvian coast (curved carapace length [CCL]...

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Section: Environmental Factorssupporting

confidence: 50%

Post-capture movements of loggerhead turtles in the southeastern Pacific Ocean assessed by satellite tracking

Mangel

Alfaro‐Shigueto²,

Witt³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…This species may be significantly associated with large oceanographic anomalies, such as fronts and currents (Polovina et al 2004(Polovina et al , 2006, where food for loggerheads may be more abundant. Etnoyer et al (2006) also found topographic features like the shelf break and seamounts to be unimportant factors in explaining the distribution of these turtles. Loggerheads, however, may use the magnetic signatures of seamounts for large-scale navigation proposes (Lohmann & Lohmann 2003).…”

Section: Discussionmentioning

confidence: 99%

Evidence of a seamount effect on aggregating visitors

Morato¹,

Varkey²,

Damaso³

et al. 2008

Mar. Ecol. Prog. Ser.

178

134

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It has been suggested that seamounts hold higher abundances of some 'visiting' animals, such as tuna, sharks, billfishes, marine mammals, sea-turtles and even seabirds, but this has been based on sparse records, and warrants further examination. In this paper we use data from a fishery observer program to examine whether the predicted higher abundances of tuna, marine mammals, sea turtles and seabirds actually occur around Azores seamounts and to map the distribution of the various species. Our results indicate that some marine predators (skipjack Katsuwonus pelamis and bigeye tuna Thunnus obesus, common dolphin Delphinus delphis and Cory's shearwater Calonectris diomedea borealis) were significantly more abundant in the vicinity of some shallowwater seamount summits. Our methodology, however, failed to demonstrate a seamount association for bottlenose dolphins Tursiops truncatus, spotted dolphin Stenella frontalis, sperm whale Physeter macrocephalus, terns Sterna hirundo and S. dougalli, yellow-legged gull Larus cachinnans atlantis and loggerhead sea turtles Caretta caretta. Seamounts may act as feeding stations for some of these visitors. Not all seamounts, however, seemed to be equally important for these associations. Only seamounts shallower than 400 m depth showed significant aggregation effects. These seamounts may be considered hotspots of marine life in the Azores, and a special effort should be made in order to ensure a sustainable management of these habitats.

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“…Since 2004, CalCOFI cruises have included systematic marine mammal visual and acoustic surveys, providing an opportunity to investigate the relationship of top marine predators to these numerous habitat variables. Previous studies in the CCE have found that baleen whale distributions are related to season and environmental variables, including bathymetry, sea surface temperature, salinity, location of fronts, chlorophyll concentration, and acoustic backscatter (Smith et al 1986;Burtenshaw et al 2004;Keiper et al 2005;Tynan et al 2005;Etnoyer et al 2006). However, habitat models are often limited by small sample sizes due to infrequent surveys/low numbers of sightings, lack of data during winter months when surveys are not typically conducted, and/or by availability of oceanographic data.…”

Section: Introductionmentioning

confidence: 99%

“…Baleen whales forage primarily in summer and typically migrate to lower-latitude breeding and calving grounds in winter, although wintering grounds and movement patterns of fin whales are not well known (Mate et al 1999, Etnoyer et al 2006. Whaling records from the early 20 th century and recent surveys over the past twenty years indicate that blue and fin whales are most abundant off the coast of California in summer and fall (but also seen occasionally in winter), whereas humpbacks were seen near the coast in summer but further offshore in winter (Clapham et al 1997;.…”

Section: Introductionmentioning

confidence: 99%

Marine Mammal Acoustic Monitoring and Habitat Investigation, Southern California Offshore Region

Hildebrand¹

2009

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington headquarters Services SPONSORING / MONITORING AGENCY REPORT NUMBER NPS-OC-09-00611. SUPPLEMENTARY NOTES The views expressed in this technical report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government. 12a. DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. 12b. DISTRIBUTION CODE ABSTRACT (maximum 200 words)This report summarizes work conducted in FY2007-FY2008 to conduct marine mammal monitoring and habitat investigations in the southern California offshore region. The report describes marine mammal monitoring results during quarterly cruises, and models how physical and biological oceanographic conditions affect marine mammal habitat. Additionally, progress with constructing automatic detection and classification algorithms for acoustic monitoring of marine mammals is summarized, as is work on finite element modeling of acoustic propagation within the bodies of beaked whales and related marine mammals.Some highlights:[1] Data collected (July 2004 support the hypothesis that distributions of foraging large whales are linked to cold surface temperatures. However, winter distributions of migrating large whales don't appear to be related to habitat variables analyzed herein, and may be harder to predict based on oceanographic data.[2] A species classifier which decides whether short groups of clicks are produced by one or more individuals from three particular species is presented. The system uses the Teager energy operator and cepstral analysis.[3] Anatomical investigations and computer finite element modeling with marine mammal bodies were conducted, which resulted in two methodological advancements and the addition of more beaked whale species to the Digital Library of Anatomy. NUMBER OF PAGES 69 SUBJECT TERMS

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Sea-surface temperature gradients across blue whale and sea turtle foraging trajectories off the Baja California Peninsula, Mexico

Cited by 96 publications

References 40 publications

Post-capture movements of loggerhead turtles in the southeastern Pacific Ocean assessed by satellite tracking

Post-capture movements of loggerhead turtles in the southeastern Pacific Ocean assessed by satellite tracking

Evidence of a seamount effect on aggregating visitors

Marine Mammal Acoustic Monitoring and Habitat Investigation, Southern California Offshore Region

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