June 18, 2008 -- Scientists have long debated how best to protect some of our most charismatic ocean denizens: albatross, sea turtles, sharks, and dolphins, all of which are often caught as bycatch in marine fisheries.
And now disagreement has emerged over a plan proposed last year that would have fishermen pay a fee for every seabird caught on a long line. That money, in turn, would be used to help seabirds everywhere, including eradicating non-native rats that prey on the birds' eggs on breeding islands.
This could be a more economical and politically acceptable approach to reducing deaths, argued the authors of the 2007 study, published in Frontiers in Ecology and the Environment.
It proved to be a controversial idea, and now another team of researchers has published an article urging caution in applying bycatch offsets in real-world situations.
One of the main arguments of the new study is that an adult seabird or sea turtle of breeding age -- the type of animal most likely to be caught as bycatch -- contributes far more to keeping the population going than a hatchling. The hatchling has many obstacles to conquer before it becomes a breeding adult, often years down the line.
The authors of the new article, published this week in PLoS ONE, point out that 588 hatchling loggerhead sea turtles would have to be saved to balance the loss of a single adult.
"There are many more things that can be done with fishing policy and gear changes to reduce the harm that really is there, rather than some kind of alluring proposal that may not do anything and that we fear could do more harm by allowing an activity to go on," said study author Vickie Bakker of the University of California, Santa Cruz.
The researchers point out that for species like sharks and dolphins that don't leave the water, there is no opportunity to offset bycatch. Also, they argue that islands where rats threaten seabirds do not contribute as much to the population as the islands where rats are not present -- but bycatch takes breeding adults from all of these islands.
The authors of the original study defend the idea of bycatch offsets. "It's not a substitute for current mitigation or regulation," said Josh Donlan of Cornell University in Ithaca, N.Y. and an author of the original study, "but it is a useful additional strategy."
A large working group of scientists and economists in both public and private arenas is trying to develop a framework for putting offsets into practice, Donlan said. He is also the head of Advanced Conservation Strategies, a non-profit organization engaged in this work.
He said that the new study was disappointing. "They completely ignored economics, and they talk little about the realities of social politics in the high seas."
"In much of the paper they're comparing not to what is happening now, but to some lofty goal," he added.
The original study's other author, Chris Wilcox of the Commonwealth Scientific and Industrial Research Organization, Australia's national research body, noted that if it takes 588 turtle hatchlings to equal one adult, saving hatchlings could still be a good idea if it costs 50 cents to save a hatchling and $10,000 to reduce bycatch of an additional adult.
"Offsets are the only thing you can do to go back and reduce past errors," he said. "Ultimately even new gear may kill seabirds."
The authors of the new study think bycatch offsets may have a place, but that several criteria need to be met before it should be implemented.
"The good part about [the original] paper is that it tries to present other, innovative approaches to reducing bycatch," said author Rebecca Lewison, of San Diego State University. "But there were some flaws with their case study that we couldn't let sit. If we can overcome the flaws, let's do it."
"I don't know if it has to have as much impact as bycatch reduction for it to be a good idea," she added. "We have to be protecting on beaches and we have to be protecting critters in the water."
Related Links:
Discovery News blog: EnvironMental Case
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