Thursday, July 03, 2014
Photo-Identifying the Green Sea Turtles in the San Gabriel River
Since 2008 I’ve been photographing the urban green sea turtles in the San Gabriel River supplanting the field notes taken by my wife Pam. The portion of the river which runs between Orange County and Long Beach has the northern most colony of green sea turtles in the world. This colony was little known until recently. It is one of Nature’s best kept secrets in Southern California. Our field observation is part of a larger sea turtle field research effort that is being coordinated by the National Marine Fisheries Service and the Aquarium of the Pacific. With six years of images of surfacing sea turtles on file we’ve added a new phase of our part the project, going through the photos and trying to identify individual turtles.
This photo ID effort has just recently started and it could be months before we start seeing consistent results. At present we are doing it the old fashion way by eye-balling individual images and trying to match them. We are looking into software programs that can help in this effort but for now it’s the old Mark One eyeball that’s currently being used. The only high tech device that we’re using is an iPad and an app that allows images to be brought up side by side.
What we are initially using as identifying marks on the turtles are the scute patterns on their head. These marks have been used as identifying marks by researchers in other parts of the world. I went through years of images and picked out categories of potential turtles ID angles. Because of how I anticipated the swimming behaviors of the turtles and the currents in the river, the most numerous and best angled views were of the sea turtle’s right side. Other angles included the front, left side, back and overall shell view of the turtles.
When I started this photo ID effort a few weeks ago I wasn’t expecting any immediate results. However when I serendipitously picked a random image of a turtle I had recently photographed I discovered that I had photographed this same turtle a year prior. Talk about beginner’s luck!
Stay tuned as we attempt to unlock more secrets of the urban sea turtles of the San Gabriel River.
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