NOAA Scientist and Upwell project partner, Scott Benson, coordinates studies of the distribution, abundance, movement patterns, foraging ecology, and health of endangered western Pacific leatherback turtles along the U.S. West Coast and throughout the Pacific. Since 1986, Scott has been involved in ecological research and conservation of marine vertebrates in the Pacific Ocean, including integrated studies of marine mammals and seabirds along the U.S. West Coast. Stationed at Moss Landing Marine Laboratories, Scott and the NOAA team collaborate with Upwell to tag and track leatherbacks in the California Current.
Photo by Kate Cummings from Blue Ocean Whale Watch of a leatherback spotted in Monterey Bay in August 2020.
During September and October of 2019 (also known as the good ol’ days), we were able to capture and tag six leatherbacks in the Gulf of the Farallones off San Francisco, California. Most biotelemetry projects desire long deployment records that span multiple months or even a year. We programed our Wildlife Computers tags to report locations while conserving battery life in hope that the tags would continue to transmit for an entire year. Other unpredictable factors can also affect tag longevity, including attachment failure, predation, fishery bycatch, etc. Of the six tags we deployed last year, only one continues to send data on leatherback movements. The track illustrates a ‘yo-yo’ pattern, whereby the turtle moves out of the California Current and into tropical waters during the winter and spring months, and returns to the California Current during the following summer and fall. Leatherback turtles that forage off California originate from nesting beaches in the western Pacific (i.e. Indonesia, Solomon Islands); however, they only return to the nesting beaches every 2-5 years (this is called the ‘remigration interval’). Therefore, this ‘yo-yo’ pattern is very common during the non-nesting years.
Map showing the track of a leatherback tagged in 2019 by Upwell and NOAA (Permit # 21111)
The female turtle whose transmitter is still reporting was tagged on 20 September 2019, and she returned to same area where she was tagged in the Gulf of the Farallones on 31 July 2020. It’s exciting when we see one of these movement records close the loop! We expected the turtle to remain in that area through October; however, she had other plans and has moved to deeper offshore waters once again. Perhaps she found something better to eat offshore, or the sea nettles were not quite “ready” yet in the Gulf of the Farallones. We hope the tag will continue to transmit until we have an opportunity to get on the water ourselves and potentially make visual contact with the turtle…if she comes back, again.
Photo by Kate Spencer of Fast Raft Ocean Safaris spotted in the Monterey Bay in August
Meanwhile…in Monterey Bay, one leatherback was seen by Monterey Bay Whale Watch (Nancy Black) on 29 June, and three leatherbacks were sighted on 8 August by Blue Ocean Whale Watch (Kate Cummings) and Fast Raft Ocean Safaris (Kate Spencer). All three of the 8 August sightings occurred within a few miles of each other, so we weren’t sure whether they were all unique animals or re-sights of the same 1 or 2 turtles. Unlike whales, leatherbacks are notoriously difficult to follow visually on the water. Fortunately, Kate and Kate are excellent photographers, and their fine images allowed us to determine that there were indeed three unique individuals present! We thank Kate, Kate, and Nancy for reporting the sightings and sending us high quality images whenever possible.
If you’re interested in learning more about leatherback turtles, a global Status Review of the Leatherback Turtle – 2020 was published this week. It contains information about leatherback turtle populations in the Atlantic, Pacific, and Indian Oceans.