Watching the sun rise over San Francisco’s skyline while on my way to the docks to board another offshore expedition to the Farallone Islands in the Gulf of the Farallones National Marine Sanctuary is always an inspiring moment, and this Sunday was no exception! Our vessel was booked full for an entire day of searching for the rare leatherback sea turtle (Dermochelys coriacea), watching whales, and experiencing all the wildlife diversity in and around these amazing islands. I gave a short talk to our group before departure, sharing facts on the biology and ecology of Pacific leatherbacks and our conservation successes in California and Hawaii. Many of the guests had no idea leatherbacks were present offshore of California and were energized by my talk to see one and help them!
This summer has been very rewarding for our all-volunteer Leatherback Watch Program, which kicked-off with a huge party at the Cal Academy of Sciences on June 16, World Sea Turtle Day, and has tallied over twenty leatherback sightings from Point Sur, California up to British Columbia, Canada this summer and fall. The majority of the leatherbacks seen have been in California’s National Marine Sanctuaries, so our expedition to the Farallones was buoyed by high hopes that we would be rewarded with another leatherback sighting.
Within the first half an hour of smooth sailing, I spotted two floating balloons on the surface of the sea, a potentially harmful meal for feeding leatherbacks that might mistake them for jellyfish (which are also round, and float on the surface). Research shows that one-third of all leatherbacks have plastic in their stomachs, and these balloons are a grim reminder why that is true. During the two hour journey out to South Farallone Island, I spotted two more cases of plastic pollution in what is proposed to be critical habitat for the endangered leatherbacks; a mylar and another plastic balloon.
We reached the islands in just under two hours, and immediately spotted a young gray whale (Eschrichtius robustus) feeding in shallow water. As the whale meandered, we passed by two shark-diving operators, some marine researchers, and two more wildlife viewing vessels. We spotted the leatherback’s favorite food, the brown sea nettle (Chrysaora fuscescens), in the highest abundance on the leeward side of the south island, but no leatherbacks were seen. We headed offshore to the edge of the continental shelf when an offshore blow directed us to two humpback whales (Megaptera novaeangliae) feeding on what appeared in our sonar to be a dense aggregation of krill. These whales were bringing us farther and farther off course, but were thrilling to watch as they repeatedly dove to feed, showing us their flukes on several occasions. Our captain reversed our course and we headed home, passing close to middle rock, and then directly into a pod of Dall’s porpoise (Phocoenoides dalli). Three more balloons littering the Marine Sanctuary surface were spotted, but still no leatherback sea turtles.
Passing under the Golden Gate bridge on our way home, we all felt mixed emotions; sadness that we had not seen a leatherback sea turtle and that our journey was coming to an end, and elation at the amazing marine mammals we had witnessed. New friends and supporters of the Sea Turtle Restoration Project were made during hours of engaging discussions, and many of the guests left with fantastic photos of the humpbacks. We will continue to partner with the Oceanic Society in the San Francisco Bay and beyond, and look forward to joining them again for another expedition on October 29!