Are Green Sea Turtle Populations Increasing along the Texas Gulf Coast?

Green Sea Turtle
Green Sea Turtle
Picture taken by Steve D.

 

Are Green sea turtle populations increasing along the Texas gulf coast?  Along the Texas Gulf Coast there appears to be an uptick in the number of sightings of Green Sea Turtles (Chelonia mydas) and Green Sea Turtle nests on North Padre Island. While reported sightings are not uncommon, experts do appear to agree that in 2012 and the beginning of 2013 there has been an increase in the number of sighting reports. Also increasing, is the number of turtles requiring rehabilitation due to injuries from boat encounters that too often result in the immediate death of turtles, or more frequently, leave deep disfiguring wounds that are prone to infection.

The increased sightings have some scratching their heads as to what might be occurring. A few people have suggested that there are more turtles due to the reopening of Packery Channel between Mustang Island and Padre Island. These islands form a barrier between the Texas coastline and the Gulf of Mexico, cutting off Corpus Christi Bay from the ocean and giving rise to a shallow water body known as the Laguna Madre that stretches the Texas coastline from Corpus Christi into northern Mexico. Padre Island is the longest barrier island in the world and because it separates the Laguna Madre from the ocean there is only limited mixing with ocean water, which also means limited ways for sea turtles to get in. Now that Packery Channel is open, perhaps Green Sea turtles, whose favored habitat is shallow coastal areas, are visiting more frequently than was possible before.

The turtles may also be attracted by the large gardens of sea grass that grow in the Laguna Madre. Sea grass populations have grown in the upper Laguna Madre and, because the Laguna Madre has an average depth of 3.6 feet (1.1 m), there is plenty of light from the sun and nutrients in the sandy bottoms to allow healthy growth of sea grass. In fact, 75% of all of the sea grass cover along the entire Texas coast is found in the Laguna Madre. Three species of grass dominate with shoal grass being the most abundant, followed by a moderate distribution of manatee grass and a small distribution of turtle grass. There is speculation that all of this grass is just too tempting for the vegetarian Green Sea turtle to pass up, especially in light of the fact that sea grass beds in and around other gulf coast areas have disappeared from both natural causes and human activities.

Whether the increased number of sightings is the result of an  increase in the Green Sea Turtle population or more sea turtles getting in through Packery Channel may never be known. Measuring any sea turtle population is a challenge, not just because there are not enough resources to make accurate estimates, but because making the measurements often requires disturbing turtles that may lead them to abandon their nesting grounds never to return. A second difficulty is that Green Sea Turtles that do come to shore are primarily females looking for good places to build nests. Adult males and juvenile turtles tend to stay out in the open water making population estimates unreliable.

For more information on the Green Sea Turtle and other species of sea turtle, see the associated links.
http://pubs.usgs.gov/sir/2006/5287/pdf/LagunaMadre.pdf
http://www.fws.gov/northflorida/SeaTurtles/Turtle%20Factsheets/green-sea-turtle.htm
http://www.orf.org/turtles_green.htm
http://www.utmsi.utexas.edu/outreach/animal-rehabilitation-keep.html
http://www.tpwd.state.tx.us/huntwild/wild/species/greentur/
http://www.tpwd.state.tx.us/huntwild/wild/species/ridley/
http://www.nps.gov/pais/naturescience/current-season.htm
http://www.tpwmagazine.com/archive/2012/jun/ed_3_seaturtles/

About Mark Shepherd

I work in the environmental movement helping to protect the air we breathe, the water we drink, the land that sustains us and the natural and biological resources we depend on.

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