Analysis
by Kate Sampson
Residents and visitors to the Gulf of Maine may be surprised to discover that the area is home to four sea turtle species in the spring, summer and fall. Three of these species, the green, Kemp’s ridley, and loggerhead, are hard-shelled sea turtles, meaning their shells are made up of large bony plates covered with keratin (the same protein in hair and fingernails). The last species, the leatherback sea turtle, has a shell that is not hard, but rather made up of small bones fitted together like puzzle pieces, covered with leathery skin.
Turtles Have a Complex Life History
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A Kemp’s ridley sea turtle hides in Sargassum. Credit: Kate Sampson, New England Aquarium/ Large Pelagics Research Center |
Females of all sea turtle species found in the Gulf of Maine lay their eggs on tropical or subtropical beaches along the southeast and Gulf of Mexico coasts of the United States, the Caribbean, Central America and northern South America. Nesting locations vary by species, but they share a common pattern in which they migrate south into warmer waters to nest, and north into cooler, more productive waters to feed. When hatchlings leave their nests, they quickly enter the water and swim offshore, beginning an oceanic stage, sometimes called the “lost years.” Sea turtles spend several years being carried by currents throughout the North Atlantic Ocean.
During this time, the turtles spend most of their time at the surface, associated with large mats of seaweed, called Sargassum. Sargassum provides camouflage against predators and also food in the form of small invertebrates and even the seaweed itself. After two to seven years, depending on the species, the turtles move into more coastal, nearshore habitats. These turtles are still juveniles, but at this time they range from about 4 pounds to 60 pounds (1.8 to 27 kg). It is during this coastal juvenile stage that we start to see turtles in the Gulf of Maine.
Hard-Shelled Sea Turtles, Warm-Water Residents
The most common and largest hard-shelled species in the Gulf of Maine is the loggerhead sea turtle. Loggerheads can be found as far north as Nova Scotia, Canada, but are more common in the southern Gulf of Maine. The Kemp’s ridley and green sea turtles are typically only commonly found as far north as Massachusetts Bay. Loggerhead and Kemp’s ridley turtles feed primarily on crabs and mollusks, such as whelk and mussels. The green sea turtle, on the other hand, is herbivorous; it only eats plant matter, such as sea grasses. All of these food items are found along the ocean bottom, which results in hard-shelled turtles having a shallow, coastal distribution.
All of these turtles will move south along the coast when water temperature starts to drop in the fall. However, in partially enclosed bodies of water such as Cape Cod Bay and Long Island Sound, turtles may be delayed in their southern migration and may not depart before the water temperature drops. These turtles may succumb to “cold-stunning,” in which their activity decreases or ceases and they strand on shore in need of assistance. Cold-stunned sea turtles are usually very underweight and suffer from frostbite or infections such as pneumonia, but with medical care in an area rehabilitation center they can recover and be released back into the wild.
Leatherback Sea Turtles, a Wide-Ranging Species
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A leatherback sea turtle coming to the surface to breathe. Credit: Kate Sampson, New England Aquarium/ Large Pelagics Research Center |
Leatherback sea turtles are by far the largest species of sea turtle in the world. Adult leatherbacks can measure up to 6 feet (1.8 meters) in length and over 1500 pounds. (680 kg) in weight. Due in part to their size, as well as to anatomical mechanisms to deal with cold temperatures, leatherbacks are much more cold-tolerant than hard-shelled turtles. For this reason, they can commonly be seen as far north as Nova Scotia and beyond. Leatherbacks can maintain their body temperature several degrees above the surrounding water, which is in contrast to most of their cold-blooded reptile cousins. This ability allows leatherbacks to venture farther north and to stay in the Gulf of Maine later into the fall. Leatherbacks eat jellies, such as sea nettles and lion’s mane, and are commonly found in deeper, more open ocean habitats than hard-shelled turtles.
Sea Turtles Are Endangered
All sea turtle species in U.S. waters are protected under the Endangered Species Act (ESA). Sea turtle populations are reduced from historical numbers for many reasons, including, among others, hunting and egg harvesting, alteration of nesting habitat, vessel strikes, and capture in fishing gear. The National Marine Fisheries Service (NMFS) is working to reduce threats in U.S. waters to help conserve and recover sea turtles. In Canada, leatherbacks ate protected by the Species at Risk Act (SARA). Loggerheads are not protected under SARA currently, but the Canadian Sea Turtle Network(CSTN), a non-profit organization involving scientists, commercial fishermen, and coastal community members that works to conserve endangered sea turtles, is working to have them covered by the law. Usually only these two species are found in waters off Atlantic Canada. Sightings of other species are unusual.
Keep an Eye Out for Sea Turtles
Sea turtles in the Gulf of Maine can be at risk of injury or death from vessel collisions and entanglement in fishing gear, mooring lines or marine debris. These risks are avoidable. Boaters in the Gulf of Maine can help by keeping watch for sea turtles at the surface of the water during the spring, summer and fall. For hard-shelled turtles, pay particular attention when in coastal areas in the southern Gulf of Maine. For leatherback sea turtles, watch for the presence of jellies at the surface; where there are jellies there are often leatherbacks. These species are very low profile and difficult to see, plus they do not always move out of the way of oncoming vessels in time. Slowing down and keeping a lookout for turtles would go a long way towards reducing the risk of vessel collisions.
Report Entangled Sea Turtles
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A leatherback sea turtle entangled in the buoy line of pot gear. Credit: Kate Sampson, New England Aquarium/ Large Pelagics Research Center |
Entangled turtles need immediate assistance. If you encounter an entangled sea turtle in U.S. waters, please call the NMFS northeast region hotline at: 866-755-NOAA (6622). NMFS manages a network of trained responders who can safely and completely disentangle the turtle. Entanglements can be complex and turtles, especially leatherbacks, can be difficult to work with safely. Untrained people that attempt to disentangle a turtle may injure themselves or the turtle, or may even make the entanglement worse. Any line or netting that is left on the animal can lead to the turtle’s serious injury or death over time. Cutting a turtle free of anchoring gear may still leave the turtle with a life-threatening entanglement and yet make it difficult or impossible to relocate the turtle to assist it in the future. The best way to assist an entangled turtle is to immediately report it to the NMFS hotline and stand by the animal until responders arrive, ensuring that they can relocate and help the turtle.
If you encounter an entangled sea turtle in the Gulf of Maine, please call the National Marine Fisheries Service hotline at: 866-755-NOAA (6622).
Or,
When reporting a sea turtle in distress, it is extremely valuable for you to stay with it until a response team arrives. Turtles are very difficult to relocate if the reporting vessel does not stand by. If possible, take photographs of the turtle.
The State of the World’s Sea Turtles
http://www.conservation.org/publications/Pages/swot_4_report.aspx
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