A new study shows that controlling predators like rats would do much more to protect seabirds than enforcing stringent controls on the fishing industry.
Photo by Mr Ed Melvin, US National Marine Fisheries Service.

Removing predators could offset seabird ‘bycatch’ losses

Reducing the impact of fisheries on bycatch

“Australian Commonwealth fisheries have made strong efforts towards reducing bycatch, including modifying fishing gear and restricting areas and periods of fishing, but these measures are not always effective, leading to costly interventions such as fishery closure,” Dr Wilcox says.

 “While the priority should always be for fishers to avoid bycatch, they could also ‘offset’ the bycatch that does occur by funding conservation measures that tackle other, often greater, threats to bycatch-affected species.”

Dr Wilcox and C. Josh Donlan of Cornell University explored the offset approach in a study of flesh-footed shearwater bycatch in the ETBF, which targets yellowfin and bigeye tuna, albacore and billfish.

Practices used in the ETBF to reduce the capture of seabirds on longlines are costly and not always effective for all species. A species of concern is the flesh-footed shearwater, which in eastern Australia breeds only on Lord Howe Island where rats are potentially a major predator.

Dr Wilcox and Mr Donlan compared the potential impact of fishing with that of rat predation on Lord Howe Island flesh-footed shearwater populations, and the costs and benefits of rat control and fishery closures.

They found that banning fishing in a 750-kilometre radius of the island would result in a six per cent increase in growth rate of the shearwater population, at a cost of about A$3.5 million. The eradication of rats would result in a 32 per cent increase in the population growth rate, at a cost of about A$580,000.

Rat eradication therefore could yield a conservation return on investment 23 times greater than a fishery closure, and could have broader ecosystem benefits.

“Vessel levies could be set at the cost of offsetting their bycatch,” Dr Wilcox says. “As well as funding actions that effectively offset the bycatch, the levy would encourage fishers to seek innovative ways of avoiding bycatch.”

He says environmental groups have made great strides in drawing attention to the bycatch problem. Fishers, technologists and scientists in turn have reduced bycatch substantially through fishing-method innovation.

“For fisheries to have a zero impact on bycatch, however, they will need to use the full suite of cost-effective tools available, in a responsible and integrated way,” Dr Wilcox says.

Dr Wilcox and Mr Donlan believe that given the number of seabirds and other mammals affected by fisheries and invasive species, the offset approach could prove effective in many scenarios worldwide.

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