Green Turtle Research and Conservation in Southern California

From the beginning of the 1900s through the early 1990s they were legally harvested in many areas of the eastern Pacific. Their eggs and meat were prized food items for generations. However, with the onset of nesting beach protections in the late 1970s, coupled with protection in foraging areas starting in the mid-1990s, green turtles have made a remarkable comeback. For example, at Playa Colola, Mexico, the largest green turtle beach in the eastern Pacific, annual nesting in the mid-1980s was close to 250 females per year. Fast forward to 2015 and on that same 5-km stretch of beach, more than 1,000 females nested in a single night! Naturally, this has resulted in a major increase in green turtles throughout the region. So much so that we can expect green turtles to become a more and more common visitor to our waters for years to come.

In collaboration with other local and federal agencies and universities in the area (Unified Port of San Diego, U.S. Navy, U.S. Fish and Wildlife Service, San Diego State University, Scripps Institution of Oceanography, Long Beach State University), researchers at SWFSC have been studying green turtles in San Diego Bay for over 20 years; these studies have focused on genetics, movements, growth, toxicology, foraging ecology, and demography. We’ve also conducted fieldwork in Seal Beach National Wildlife Refuge and the San Gabriel River, both in Orange County. Most recently, we launched a citizen science project aimed at studying the green turtles living near La Jolla Cove, just down the street from the Southwest Fisheries Science Center in La Jolla, CA.

Green Turtle at Old Power Plant in San Diego Bay. Photo: NOAA Fisheries

Here are some things we have found about green turtles in southern California:

• They often stay in south San Diego Bay unless they are traveling to their nesting beach
• There are approximately 60 turtles in San Diego Bay, although the number fluctuates from year to year
• They eat eelgrass and invertebrates that are found within eelgrass beds
• While a power plant was in operation (1960-2009), these turtles grew very fast – among the fastest growth rates ever recorded for green turtles
• The largest recorded east Pacific green turtle is from San Diego Bay and weighed 540 lbs (245 kg)
• High concentrations of heavy metals and organic pollutants have been found in their scutes and blood, yet negative effects have not been found
• Incidents of boat strikes are increasing in recent years in southern California

You Too Can Help!

With more eyes and smartphones with cameras on the water, we are  learning more about green turtles in southern California and you can help in this effort! If you see a green turtle or any other sea turtle species, please fill out our Sea Turtle Sightings Survey!  This form asks for basic information about your sighting, including the date, time, location, and behavior. We appreciate your help in gathering data on sea turtles because this information helps us learn more about where and when sea turtles occur in our Pacific waters! 

Sea Turtle Sightings Survey full link:

https://survey123.arcgis.com/share/ddb6e7a3f2f94d85b7391e4d537ca57b?portalUrl=https://maps.fisheries.noaa.gov/portal

Select Publications from Our Team

Allen CD, Robbins MN, Eguchi T, Owens DW, Meylan AB, Meylan PA, Kellar NM, Schwenter JA, Nollens HH, LeRoux RA, Dutton PH, Seminoff JA. 2015. First assessment of the sex ratio for an East Pacific green sea turtle foraging aggregation: validation and application of a testosterone ELISA. PLoS ONE 10: e0138861.

Crear DP, Lawson DD, Seminoff JA, Eguchi T, Le Roux RA, Lowe CG. 2016. Seasonal shifts in the movement and distribution of green sea turtles Chelonia mydas in response to anthropogenically altered water temperatures. Marine Ecology Progress Series 548, 219-232.

Crear DP, Lawson DD, Seminoff JA, Eguchi T, LeRoux RA, Lowe CG. 2017. Habitat use and behavior of the East Pacific green turtle, Chelonia mydas in an urbanized system. Bulletin of the Southern California Academy of Sciences 116:17-32.

Eguchi T, Seminoff JA, LeRoux RA, Dutton PH, Dutton DL. 2010. Abundance and survival rates of green turtles in an urban environment: coexistence of humans and an endangered species. Marine Biology 157:1869-1877.

Eguchi T, Seminoff JA, LeRoux RA, Prosperi D, Dutton DL, Dutton PH. 2012. Morphology and growth rates of the green sea turtle (Chelonia mydas) in a northern-most temperate foraging ground. Herpetologica 68: 76-87.

Komoroske LM, Lewison RL, Seminoff JA, Deheyn DD, Dutton PH. 2011. Pollutants and the health of green sea turtles resident to an urbanized estuary in San Diego, CA. Chemosphere 84: 544-552.

Lemons G, Lewison R, Komoroske L, Gaos A, Lai C-T, Dutton PH, Eguchi T, LeRoux R, Seminoff JA. 2011. Trophic ecology of green sea turtles in a highly urbanized bay: Insights from stable isotopes and mixing models. Journal of Experimental Marine Biology and Ecology 405: 25-32.

MacDonald BD, Madrak SV, Lewison RL, Seminoff JA, Eguchi T. 2013. Fine scale diel movement of the east Pacific green turtle, Chelonia mydas, in a highly urbanized foraging environment. Journal of Experimental Marine Biology and Ecology 443: 56-64.

MacDonald B, Lewison R, Madrak S, Seminoff J, Eguchi T. 2012. Home ranges of East Pacific green turtles Chelonia mydas in a highly urbanized temperate foraging ground. Marine Ecology Progress Series 461: 211-221.

Madrak SV, Lewison RL, Seminoff JA, Eguchi T. 2016. Characterizing response of East Pacific green turtles to changing temperatures: using acoustic telemetry in a highly urbanized environment. Animal Biotelemetry 4:22.

Turner Tomaszewicz C, Seminoff JA. 2012. Turning off the heat: Impacts of power plant decommissioning on green turtle research in San Diego Bay. Coastal Management 40: 73-87.