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Strandings data point to more than shrimpers in the deaths of Turtles.
The recent spike in sea turtle mortality along the Gulf coast has raised several concerns over the cause of these deaths and how to stop it.
Source: 1987-2007, 2008-2011. Decadal averages in Turtle strandings by month, compared to the monthly strandings 2010 and 2011. Note the above average strandings begin in April 2010 and continue in the early months of 2011.
geographic range of strandings displayed above
One way we can detect changes in turtle deaths is the changes in the number of strandings over time. A stranding is a turtle found not moving, occasionally alive but usually dead. Strandings are usually reported onshore, as the animals are washed up dead by the tides. In 2010, many more strandings were reported at sea; those are excluded here but visible on the ERMA website (under “wildlife observations, turtle and marine mammal…”).
Sea Turtles are often caught in shrimp nets, so that trawling vessels have been required to install Turtle Excluder Devices. Shrimpers have claimed that there was no difference in compliance in the TED regulations, which seems to be borne out by a recent report from NOAA. There appear to have been a low number of vessels on the water in the areas where stranded turtles were found and necropsied.
Although the 26 necropsies conducted by NOAA did not show any visible external or internal oil in these animals and suggest that these animals died by drowning, this does not mean that the presence of degraded oil and its byproducts had no effect. The default hypothesis for any sick crabs, red snapper, dolphins, or turtles should be that the massive, chronic chemical exposure has had an effect since 2010. Even now, sea animals are testing positive for Deepwater Horizon’s oil.
It seems unlikely that the sea turtles would be washing ashore in historically unprecedented numbers solely on account of shrimpers’ nets, given that the overall number of vessels has been declining, and was very low at the specific times that the large amount of turtle strandings were spotted. There seem to have been few nets out when and where most of the bodies washed ashore—so we can’t escape the obvious culprit.
Oil throughout the Gulf of Mexico could have several potential impacts on the health of sea turtles, and adds to the different stresses the animal must face. A turtle that is sick or dying is more likely to feed off of shrimp bycatch, increasing its chances of becoming tangled in a shrimping net. A sick sea turtle may be drowned by becoming caught in a net, but a sick turtle may also aspirate sand.
It is important to conduct thorough necropsies of these sea turtles in order to determine the true cause of death, although the stranded animals are often not reported in time for proper analysis. NOAA is also testing skin samples for biotoxins of concern, but the results of these tests are not yet known.
The NRDA trustees must not rule out a "chronic exposure" scenario for the dead dolphins and turtles, because we are seeing sick sea animals and people throughout the food chain, from crabs and red snapper to dolphins and people. Even if oiling is not the direct cause of death, consumption of oiled shrimp and fish could very likely be causing illness and death in sea turtles, dolphins, and people.
Part of the Solution
The Southern Shrimp Alliance has proposed a $10.8 million dollar project to the NRDA Trustees to provide a complete set of new TEDs to all shrimp fishing vessels required to use them in the Gulf and South Atlantic.[i] TEDs are significantly effective in reducing injury and mortality of sea turtles and other species of concern, but this effectiveness declines over time. The cost to purchase a new TED is prohibitively high in the shrimp fishery, which discourages shrimpers from purchasing new TEDs.
Other NRDA projects proposed
Another conservation measure that takes special urgency is designation of critical habitat for the Kemp’s Ridley under the Endangered Species Act. Prior to the spill, Kemp’s Ridley was and continues to be threatened by habitat degradation, pollution, and different types of fishing activity. Designating[ii] and patrolling[iii] key nesting beaches and marine habitats in the Gulf of Mexico as critical habitat for the Kemp’s Ridley is key to ensuring species survival.
The circumstantial evidence of observed trends in strandings over time as well as the recent decline in shrimping show that we cannot assign the majority of recently sea turtle deaths to shrimpers. We must not turn our attention from the more likely culprit, BP, and ensure that they are not let off the hook for killing sea turtles.
Stephanie Stephanski is a Intern for Gulf Restoration Network. Scott Eustis is the Coastal Wetland Specialist for GRN.
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