Sea turtles are found in San Diego waters, making the region a unique habitat along the Pacific coast of North America. This localized phenomenon involves a year-round foraging population utilizing the area’s rich coastal resources. Their sustained presence is tied to specific environmental factors that provide a temporary sanctuary. Scientists closely monitor the population, treating the area as an important study site for understanding the species’ life history in cooler, temperate zones.
Identifying the San Diego Sea Turtle Population
The sea turtles that inhabit San Diego are almost exclusively the East Pacific Green Sea Turtle (Chelonia mydas), a distinct population segment. This population is sometimes colloquially referred to as the “black sea turtle” due to a darker coloration of its carapace, or shell, compared to other green turtle populations. Distinguishing features include a narrower, more dome-shaped carapace that is generally smooth and lacks a prominent keel. These turtles possess a relatively small head and large, single-clawed flippers, which they use for powerful propulsion through the water.
The turtles found foraging in San Diego Bay and the nearby coastal areas are primarily juveniles and sub-adults, although fully grown adults are also present. These individuals originate from nesting beaches hundreds of miles away, mainly along the Pacific coast of Mexico, such as those in Michoacán. Once hatched, they travel north to productive feeding grounds like San Diego, where they spend many years growing before migrating back to their original nesting sites to reproduce. While other species, such as the Loggerhead, may occasionally pass through, the resident, long-term population is defined by the Green Sea Turtle.
Key Habitats and Foraging Behavior
The sustained presence of Green Sea Turtles in San Diego is linked to two critical resources: an abundant food source and historically warmer water temperatures. The primary foraging habitat is the shallow-water ecosystem of San Diego Bay, particularly the southern portion. This area contains expansive beds of Zostera marina, or eelgrass, which forms the core of the adult Green Sea Turtle’s herbivorous diet.
These turtles select for these dense eelgrass meadows, supplementing their diet with invertebrates found living within the seagrass beds. For decades, the turtles’ habitat use was heavily influenced by the presence of the South Bay Power Plant (SBPP), which operated from 1960 to 2010. The plant utilized a “once-through cooling” system, discharging warm effluent water into the bay that was several degrees warmer than the ambient water temperature. This artificially heated water created a thermal refuge, especially during the cooler winter months, allowing the cold-blooded reptiles to maintain a higher body temperature and metabolism.
The warm water access was a significant factor in the population’s success, leading to some of the fastest recorded growth rates for the species globally. Following the decommissioning of the SBPP, researchers observed a decrease in the concentration of turtles near the former discharge site as water temperatures returned to more natural levels. Despite this change, the population has persisted, relying on the extensive eelgrass habitat and demonstrating continued year-round residency in the bay’s productive waters.
Conservation Status and Safe Viewing Practices
The East Pacific Green Sea Turtle population found in San Diego is legally protected under federal law, reflecting its vulnerable status. This Distinct Population Segment (DPS) is currently listed as Threatened under the Endangered Species Act (ESA). This federal designation prohibits the harassment, harm, pursuit, wounding, capture, or killing of the turtles, making it illegal for the public to interact with them in ways that alter their natural behavior.
Given the protected status of these animals, turtle welfare must be the highest priority during any encounter. When viewing sea turtles from a boat or kayak, federal guidelines recommend maintaining a distance of at least 50 yards. This distance helps prevent disturbance and allows the turtles to surface and rest without interference. Never attempt to feed, touch, or swim with the turtles, as direct interaction is considered a form of harassment under the ESA.
Boaters should be especially mindful of their speed in known foraging areas, as vessel strikes are a growing threat to the population. If a sea turtle is observed, boaters should slow down, operate at a no-wake speed, and place engines in neutral until the animal has passed safely. If the public encounters a hooked, injured, or stranded sea turtle in California, immediately contact the NOAA Stranding Network. Reporting the exact location and condition of the animal allows trained professionals to respond, ensuring the best chance for the turtle’s recovery. The official number for the West Coast Stranding Network is +1 (562) 506-4315.