East Pacific Green Turtle by Isabella Hamman

East Pacific Green Turtle (Chelonia mydas)

 

1. Summary of the Description and the Ecology of the East Pacific Green Turtle:

The East Pacific Green Turtle differs from the more commonly known green turtle in size, color, and shell shape. The shell, or carapace, of the adult East Pacific Green Turtle is “narrower, more strongly vaulted, and more indented over the rear flippers than that of the green turtle” (page 6). In addition, the East Pacific Green Turtle is much lighter and smaller than the green turtle and also produced much smaller hatchlings, in comparison. In regards to color, the hatchling East Pacific Green turtle is typically black or dark grey, the juvenile is “brightly colored with a mottled or radiating carapacial pattern of light and dark brown, reddish brown, olive and yellow” (page 6). 

The East Pacific Green Turtle typically feeds along the west coast of Baja California and eats a herbivorous diet, mainly consisting of sea grasses and algae, with the occasional marine animal thrown in when available.

In terms of growth rate, time to reach sexuality maturity, and reproductive characteristics; the East Pacific Green Turtle is certainly a K-selected species. In most cases, it takes juveniles at least 50 years to reach sexuality maturity, with a measly growth rate of 0.40 – 0.45 cm/year. Reproduction is seasonal in the case of this species, closely tied to migratory patterns. Females travel extraordinary distances in order to copulate and then nest.

2. Geographic and Population Changes of the East Pacific Green Turtle:

Due to the fact that sea turtles are highly migratory, it is difficult to assess the true geographic range of the East Pacific Green Turtle. However, this population of sea turtle is mainly located in the eastern pacific (in U.S. waters) and in certain parts of Mexico (but such turtles are in Mexico’s jurisdiction, not the U.S. and EPA’s). In general, the range of the East Pacific Green turtle stretched from Canada, to the western coasts of the United States, and down into Mexico.

In regards to its historical range, the East Pacific Green Turtle could be found in abundance in the eastern Pacific from Baja California to Peru and to the Galapagos Islands. The species found plentiful feeding grounds in the Gulf of California. However, this geographical range existed prior to the vast commercial exploitation of the East Pacific Green Turtle. By the late 1970’s, the East Pacific Green Turtle was “virtually extirpated” from the Gulf of California. This excessive exploitation of the East Pacific Green Turtle has caused a drastic decline in its population size. This pattern can be observed in Michoacán, Mexico (where 1/3 of all East Pacific Green Turtles nest), in which population declines have been steady and significant over the last 40 years. In today’s world, it is extremely rare to see East Pacific Green Turtles in the Gulf of California, and even rarer to see one that is beyond the juvenile stage.

 

3. Listing Date and Type of Listing of the East Pacific Green Turtle:

The East Pacific Green Turtle was listed on the ESA on January 12, 1998. According to the U.S. Endangered Species Act of 1973, the breeding populations of the East Pacific Green turtle, from the Pacific coast of Mexico, as listed as Endangered.

4. Cause of Listing and Main Threats to the East Pacific Green Turtle:

The East Pacific Green Turtle was listed under the ESA because of its exhibition of an extreme population decline over the last 30 years. According to the ESA, this decline can be attributed to the “massive over-harvest of wintering turtles in the Sea of Cortez between 1950 and 1970”, as well as the “intense collection of eggs between 1960 and 1980 on the mainland beaches of Mexico” (page vi).

The East Pacific Green Turtle is faces several different threats. Due to the lack of knowledge of the whereabouts and amount of these turtles in the northeastern Pacific, the vital (suspected) foraging areas of the turtle, such as within the bays and inlets along the coast of Baja California and Southern California, cannot be put under protection of the ESA. This lack of knowledge on the whereabouts of large proportions of the population of East Pacific Green Turtle also prevents policy-makers and scientists from protecting the turtles from possible threats while migrating. Regional threats posed to the species along the West Coast of the United States include: debris, boat collisions, and incidental capture. Regional threats posed in Mexican waters include the (illegal) harvest of turtles and their eggs. These threats cause damage to a widespread variety of aspects of the East Pacific Green Turtle’s livelihood.

Threats to the species’ nesting environment include, but are not limited to:

1.     Directed Take: The harvest of sea turtles and their eggs for food or any other commercial use.

2.     Increased Human Presence: The rapidly increasing human population in many areas surrounding the Pacific Ocean is causing increasing pressure on the limited coastal resources that man and marine life must share. Examples include loss of nesting habitat to human recreational use of beaches, beaching camping/fires, and an increase of litter on the beaches.

Threats to the species’ marine environment include, but are not limited to:

1.     Environmental Contaminants: Chemical contamination of the marine environment due to sewage and especially agricultural runoff has been shown to cause lesions and mortality to a wide variety of marine life. 

2.     Debris (Entanglement and Ingestion): East Pacific Green Turtles are vulnerable to becoming entangled in abandoned fishing gar, ingestion of debris such as plastic bags, plastic sheets, Styrofoam, and other trash that we dispose into our waterways.

3.     Fisheries (Incidental Take): Sea turtles are all to commonly caught as collateral damage in big-rig fishing.

            In addition to the above threats, the ESA lists he Mexican fisheries that smuggle poached turtles from Michoacán for meat to be the “far most important factor in the collapse of the East Pacific Green Turtle” (page 5). From 1965 to 1977 more than 165,000 East Pacific Green Turtles were harvested in the Mexican Pacific.

5. Description of Recovery Plan for the East Pacific Green Turtle:

The recovery plan objective for the East Pacific Green Turtle is to delist the regionally important population. In order to do so, the ESA determined that the population must meet the following example criteria, along with many others:

1.     Each stock must average 5,000 (or a biologically reasonable estimate based on the goal of maintaining a stable population) for over six years

2.     Nesting populations at “source beaches” are either stable or increasing over a 25-year monitoring period.

3.     Existing foraging areas are maintained as healthy environments.

4.     International agreements are in place to protect shared stocks.

The ESA states that there are 6 major actions that must take place in order for recovery to happen, in no order:

1.     Minimize boat collision mortalities, particularly within San Diego County, California.

2.     Minimize incidental mortalities of turtles by commercial fishing operations.

3.     Support the efforts of Mexico and the countries of Central America to census and protect nesting East Pacific Green Turtles, their eggs, and nesting beaches.

4.     Determine population size and status in U.S. waters through regular surveys.

5.     Identify stock home range(s) using DNA analysis.

6.     Identify and protect primary foraging areas in U.S. jurisdiction

Personal Actions:

Personally, I can, along with all others, ensure that my trash does not end up in the ocean. In addition, I can significantly reduce the amount of plastic bags, bottles, and straws I use in my everyday consumerism. Also, people can refuse to camp on beaches of turtle nesting sites - we must remember to share our beautiful beaches with the marine life that inhabits them. Lastly, we can promote the destruction of the Mexican industries that process sea turtle leather as well as other goods/delicacies that harm the East Pacific Sea Turtle.

I believe that recognizing that we, as college students, are not only part of the problem, but also part of the solution is the first and perhaps the most important step in saving the East Pacific Green Turtle.

References:

Recovery Plan for U.S. Pacific Populations of the East Pacific Green Turtle (Chelonia mydas) prepared by the Pacific Sea Turtle Recovery Team for National Marine Fisheries Service, Silver Spring, Maryland and Pacific Region, U.S. Fish and Wildlife Service, Portland, Oregon.      http://ecos.fws.gov/docs/recovery_plan/981201f.pdf