Scientific Approach & Hypotheses
Until recently, scientists had no clear understanding of the mechanisms by which Japanese loggerheads migrate across the entire North Pacific Ocean to Baja California. The thermal corridor hypothesis (TCH; Briscoe et al. 2021) proposes that loggerheads at the east end of the Central North Pacific (CNP) convergence zone can access the west coast of North America only under anomalously warm conditions (3-month running mean of SST anomalies ≥ 0.5 deg C). Under cool conditions (3-month running mean of SST anomalies ≤ -0.5 deg C), we hypothesize that loggerhead juveniles will turn back to the west.
The Sea Turtle Research Experiment on the Thermal Corridor Hypothesis ("STRETCH") will test this hypothesis by deploying cohorts of satellite-tagged loggerheads in the Eastern North Pacific. We propose an “experimental oceanography” approach—by releasing experimental cohorts of 25 juvenile loggerheads per year over four years, we will be able to provide a novel field-test of the TCH.
In addition, the release of 100 turtles (25 per year over 4 years) in the east end of the CNP convergence zone will also set the stage for us to understand what drives changes in these migratory pathways under climate variability and directional climate change. These new data will allow a full exploration of loggerhead movements in the Eastern North Pacific, setting the stage for predictive species distribution models.
The Sea Turtle Research Experiment on the Thermal Corridor Hypothesis ("STRETCH") will test this hypothesis by deploying cohorts of satellite-tagged loggerheads in the Eastern North Pacific. We propose an “experimental oceanography” approach—by releasing experimental cohorts of 25 juvenile loggerheads per year over four years, we will be able to provide a novel field-test of the TCH.
In addition, the release of 100 turtles (25 per year over 4 years) in the east end of the CNP convergence zone will also set the stage for us to understand what drives changes in these migratory pathways under climate variability and directional climate change. These new data will allow a full exploration of loggerhead movements in the Eastern North Pacific, setting the stage for predictive species distribution models.
Project Methods & Timeline
This project will take place over four years, with 25 turtles released per yearly cohort.
For each year, we will perform the following:
For each year, we will perform the following:
Rearing
First, turtles will be reared by colleagues at the Port of Nagoya Public Aquarium (PNPA) for two years prior to deployment. Turtles will be ready for release once they are about 2 years old (20-30cm straight carapace length).
First, turtles will be reared by colleagues at the Port of Nagoya Public Aquarium (PNPA) for two years prior to deployment. Turtles will be ready for release once they are about 2 years old (20-30cm straight carapace length).
Tagging
Approximately two weeks prior to deployment, turtles will be outfitted with Smart Position and Temperature "SPOT6" satellite transmitting tags, provided by Wildlife Computers, using the most ethical and non-invasive techniques. These tags will allow us to track their horizontal movements in the water.
Attaching 25 satellite tags will take roughly 4 days to accomplish (doing 8 or 9 turtles each day). Tagged turtles were be placed into an individual "basket" that is in sea water while the rest of the tag attachments are completed. This kept each turtle separated so that they don't damage the tag antennas before they are deployed in the Central North Pacific ocean somewhere between 140 and 160 degrees west longitude. The release site will depend on the sea surface temperature and the weather (it must be fairly calm to deploy the turtles safely from the ship). Once the turtles are safely released, we should be getting location fixes from the ARGOS satellites within a few days and those locations will be updated on the map.
See the photos from our June 2023 tagging at the Port of Nagoya Public Aquarium below!
Approximately two weeks prior to deployment, turtles will be outfitted with Smart Position and Temperature "SPOT6" satellite transmitting tags, provided by Wildlife Computers, using the most ethical and non-invasive techniques. These tags will allow us to track their horizontal movements in the water.
Attaching 25 satellite tags will take roughly 4 days to accomplish (doing 8 or 9 turtles each day). Tagged turtles were be placed into an individual "basket" that is in sea water while the rest of the tag attachments are completed. This kept each turtle separated so that they don't damage the tag antennas before they are deployed in the Central North Pacific ocean somewhere between 140 and 160 degrees west longitude. The release site will depend on the sea surface temperature and the weather (it must be fairly calm to deploy the turtles safely from the ship). Once the turtles are safely released, we should be getting location fixes from the ARGOS satellites within a few days and those locations will be updated on the map.
See the photos from our June 2023 tagging at the Port of Nagoya Public Aquarium below!
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Deployment
After turtles are outfitted with their satellite tags, they will be maintained in sea water at the aquarium for a few days before being loaded at the Nagoya port on a cargo 'ship of opportunity' that is traversing across the North Pacific. They will be escorted by representatives from PNPA and Kochi University who will take good care of the turtles during the voyage and will release them from the ship at a location in the eastern part of the Central North Pacific Ocean, based on longitude and preferred sea surface temperature.
After turtles are outfitted with their satellite tags, they will be maintained in sea water at the aquarium for a few days before being loaded at the Nagoya port on a cargo 'ship of opportunity' that is traversing across the North Pacific. They will be escorted by representatives from PNPA and Kochi University who will take good care of the turtles during the voyage and will release them from the ship at a location in the eastern part of the Central North Pacific Ocean, based on longitude and preferred sea surface temperature.
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Photo credits: Port of Nagoya Public Aquarium, Kochi University, Bianca Santos
Tracking
Each turtle will be tracked daily using ARGOS so that we can follow their migratory movements and behavior under a suite of oceanographic conditions. From the data that satellite tags provide, we aim to understand how loggerhead movements may change under various ocean conditions and what habitat shifts might occur due to directional climate change.
Each turtle will be tracked daily using ARGOS so that we can follow their migratory movements and behavior under a suite of oceanographic conditions. From the data that satellite tags provide, we aim to understand how loggerhead movements may change under various ocean conditions and what habitat shifts might occur due to directional climate change.
This project will take place over four years, with 25 turtles released per yearly cohort.
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Video overview of the STRETCH project from a team trip to Japan in late 2022 (below) |
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For each turtle, we have adopted names originating from the regions that share their conservation: Japan, Hawai'i, Mexico, and USA
See the caption above to learn more about their meaning! |
A baby loggerhead sea turtle at PNPA, ready for a snack! (Photo credit: Marc Rice)
Marc Rice attaching a satellite tag to a juvenile loggerhead sea turtle (Photo credit: Marc Rice)
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Video overview of the STRETCH project as presented at the
North Pacific Marine Science Organization (PICES) Meeting in 2022 (below)
North Pacific Marine Science Organization (PICES) Meeting in 2022 (below)
Stakeholders & Partners
Because our experimental deployments occur in international waters, the stakeholders most relevant to this project include the citizens of Japan, where these loggerheads nest and will be reared, as well as the citizens of Baja California, Mexico and Southern California, USA, where tens of thousands of these turtles aggregate to feed. Under the US Endangered Species Act, NOAA has taken actions to reduce bycatch in the US longline fleet (Howell et al. 2008) and in Mexico, local communities have modified fishing gears to reduce bycatch (Peckham et al. 2007). Better understanding the oceanographic mechanisms that promote sea turtle recruitment into these areas through this research will help these management stakeholders make informed decisions.
In addition, given that sea turtles are charismatic animals that have been noted to capture public attention, citizens from nations around the world are invited to join along in this project. Because sea turtles must surface to breathe, our satellite tagged turtles will have their locations reported frequently, allowing us to immediately observe where the turtles move under different oceanographic conditions. This will provide a unique outreach opportunity given that the results of our experimental deployments can be offered to the public in near real-time. We hope that this website provides an educational opportunity to engage interested individuals around the world to learn about how loggerhead sea turtles respond to climate variation, and ultimately, to directional climate change.
Our research partnership also reaches across the North Pacific Ocean. All collaborators have been involved in the development of this research and will be actively involved in the implementation of project activities. Read more about our project team here.
In addition, given that sea turtles are charismatic animals that have been noted to capture public attention, citizens from nations around the world are invited to join along in this project. Because sea turtles must surface to breathe, our satellite tagged turtles will have their locations reported frequently, allowing us to immediately observe where the turtles move under different oceanographic conditions. This will provide a unique outreach opportunity given that the results of our experimental deployments can be offered to the public in near real-time. We hope that this website provides an educational opportunity to engage interested individuals around the world to learn about how loggerhead sea turtles respond to climate variation, and ultimately, to directional climate change.
Our research partnership also reaches across the North Pacific Ocean. All collaborators have been involved in the development of this research and will be actively involved in the implementation of project activities. Read more about our project team here.
Funding
This project was made possible by funding through the
Gordon and Betty Moore Foundation and the National Geographic Society
Gordon and Betty Moore Foundation and the National Geographic Society
Header photo credit: Unsplash.com
Photo credits: Port of Nagoya Public Aquarium, Kochi University, Laura Jim, Marc Rice, Dana Briscoe, Golden Honu Services of Oceania, Bianca Santos, Larry Crowder
Photo credits: Port of Nagoya Public Aquarium, Kochi University, Laura Jim, Marc Rice, Dana Briscoe, Golden Honu Services of Oceania, Bianca Santos, Larry Crowder
