Improvements in Fishing Equipment Seem to Be Preventing Lethal 'Bycatch'
ScienceDaily 14 Sep 11;
The number of sea turtles accidentally caught and killed in fishing gear in United States coastal waters has declined by an estimated 90 percent since 1990, according to a new study by researchers at Duke University Project GloBAL and Conservation International.
The report, published in the scientific journal Biological Conservation, credits the dramatic drop to measures that have been put into place over the last 20 years to reduce bycatch in many fisheries, as well as to overall declines in U.S. fishing activity.
The study's authors estimate that 4,600 sea turtles die each year in U.S. coastal waters.
Before measures to reduce bycatch were put in place, total sea turtle takes surpassed 300,000 annually. Of these, 70,000 turtles were killed.
The study used data collected from 1990 to 2007 by the National Marine Fisheries Service (NMFS) to determine bycatch rates across more than 20 fisheries operating in Atlantic waters from the Gulf of Mexico to the Canadian border, and in the Pacific Ocean, along the West coast and around Hawaii.
It found that overall turtle bycatch rates, including both fatal and nonfatal run-ins, have fallen about 60 percent since 1990.
Shrimp trawls in the Gulf of Mexico and southeastern U.S. accounted for up to 98 percent of all by-catch takes and deaths during the study period.
All six marine turtle species that occur in U.S. waters are categorized as threatened or endangered on the U.S. Endangered Species List. They are loggerheads, leatherbacks, hawksbills, olive ridleys, Kemp's ridleys and green sea turtles.
Bycatch is an acute threat to sea turtle populations worldwide. High bycatch rates can be indicative of unsustainable fishing practices that negatively impact the health of marine ecosystems.
"The reduction of bycatch and mortality shows important progress by NMFS, which serves as a model for reducing sea turtle bycatch in other parts of the world," says Elena Finkbeiner, a PhD student at Duke and lead author of the paper. "Our findings show that there are effective tools available for policymakers and fishing industries to reduce sea turtle bycatch, as long as they are implemented properly and consistently."
Among the mitigation strategies that have helped reduce bycatch are: the use of circle hooks and dehooking equipment in longline fisheries, to reduce the severity of turtle injuries; the use of turtle excluder devices (TEDs) in shrimp trawl nets to allow captured sea turtles to escape; and the implementation of time-area closures to restrict fishing activities at times and places turtles are most likely to be present in the highest numbers.
Piecemeal regulation remains a problem, the study notes. Sea turtles are currently managed on a fishery-by-fishery basis, which means that bycatch limits are set for each fishery without accounting for the overall population impacts of all the takes added together. This fragmented approach leads to total allowed takes that exceed what sea turtle populations can sustain.
"Bycatch limits must be set unilaterally across all U.S. fisheries with overall impacts to populations in mind, much as it's done for marine mammals," says co-author Bryan Wallace, director of science for Conservation International's Marine Flagship Species Program and adjunct faculty member at Duke's Nicholas School of the Environment.
The researchers note that actual bycatch rates are likely higher than what the study reports because in many fisheries, particularly the shrimp trawl fishery, the number of on-board observers who document bycatch on fishing vessels is low relative to the sheer volume of fishing that is occurring.
"This paper provides a baseline to examine what is working and what can be improved in preventing sea turtle bycatch," Finkbeiner says. "It (makes) a strong case for the need for increased observer coverage and bycatch reporting."
Journal Reference:
Elena M. Finkbeiner, Bryan P. Wallace, Jeffrey E. Moore, Rebecca L. Lewison, Larry B. Crowder, Andrew J. Read. Cumulative estimates of sea turtle bycatch and mortality in USA fisheries between 1990 and 2007. Biological Conservation, 2011; 144 (11): 2719 DOI: 10.1016/j.biocon.2011.07.033
US fisheries kill 4,600 sea turtles per year: study
Kerry Sheridan (AFP) Google News 14 Sep 11;
WASHINGTON — Improved fishing nets have saved tens of thousands of endangered sea turtles in recent years, but 4,600 are still dying annually, mainly in Gulf of Mexico shrimp trawls, said a US study on Wednesday.
Turtle-excluder devices (TEDs), or large holes that allow the creatures to escape from nets that nab smaller marine creatures, have helped cut back on sea turtle deaths up to 94 percent since the 1990s, said the report in the journal Biological Conservation.
The current annual death rate is a "dramatic reduction" from the estimated peak of about 71,000 before protective measures were put in place, said the Duke University-led study which examined data from the US National Marine Fisheries Service on 20 US coastal fisheries.
But major gaps remain, particularly in the Gulf of Mexico and southeastern US shrimp trawl fishery area, where the study said up to 98 percent of all turtle deaths are believed to have occurred in the past two decades.
Shrimp trawlers drag nets along the bottom of the ocean that can capture and kill sea turtles, and the six varieties included in the study are all classified as either threatened or endangered species.
The new fishing nets were introduced in the late 1980s, though design improvements were made as recently as 2003 to make the holes large enough for big turtles to fit through.
TEDs are now mandated by law, but the vast size of the Gulf of Mexico fishing area, where more than 4,700 shrimping vessels work, combined with a lack of independent observers to monitor turtle deaths, or bycatch, means conservationists are unsure how many boats are doing what they should.
"The Southeast/Gulf of Mexico Shrimp Trawl fishery accounts for the overwhelming majority of sea turtle bycatch (up to 98%) in US fisheries, but estimates of bycatch in this fishery are fraught with high uncertainty due to lack of observer coverage," the study said.
Fishing and shrimping is multibillion dollar industry and a major source of income for people in coastal regions of Florida, Louisiana and Texas, an area left reeling from the BP oil spill in 2010.
Study co-author Bryan Wallace said that pushback from the shrimping industry, along with the local culture's tendency to resist government intervention, may play a role in the small number of trained observers who go along on fishing outings to monitor sea turtle interactions.
"Shrimp trawl operations have to have TEDs in their nets installed and operating properly but there have been questions raised as to the extent of that compliance," said Wallace, science director for the Marine Flagship Species Program at Conservation International.
He added that what little scientists do know is "pretty alarming."
"Our numbers are actually likely to be under-estimates," lead author Elena Finkbeiner, of Duke University's Marine Laboratory, said in an interview with AFP.
Elizabeth Griffin Wilson, senior manager for marine wildlife at the advocacy group Oceana, said the study showed "the US approach for dealing with the capture and killing of sea turtles in fisheries is still flawed."
Wilson said Gulf shrimpers are "violating protection measures that allow sea turtles to escape from their nets. As few as 21 percent of shrimp trawl vessels are complying with sea turtle protection measures."
The study authors urged a more comprehensive approach to sea turtle protection, one that moves away from the current practice in which individual fisheries gain government permission to kill a certain number of turtles per year.
"We need to take cumulative accounts of how these fisheries are impacting the sea turtle population and understand how many sea turtles in all can we take in all southeast fisheries in order for this population to still be a viable population," said Finkbeiner.
