OSU, fishing industry work to curb seabirds caught in gear

A collaborative project between researchers and the West Coast sablefish fishing industry is showing promise for reducing the number of seabirds caught in longline fishing gear, in particular several albatross species including one threatened with extinction.

The combination of using streamer lines (also called bird-scaring lines) to protect longline fishing gear from seabird attacks on baits, and setting hooks at night when the birds are less active can significantly reduce seabird mortality, the researchers say.

Results of the study were just published in the journal Fisheries Research.

“The project was a great example of collaboration between researchers and industry,” said Amanda Gladics, a coastal fisheries specialist with the Oregon Sea Grant program based at Oregon State University and lead author on the study. “The fishermen invited us out onto their boats and provided us with a lot of insights.

“It was their idea for us to explore whether fishing at night could prevent albatross bycatch on the U.S. West Coast – and it turned out, that was the case. We were thrilled to find that albatross bycatch could be reduced without increasing bycatch of other non-target species or reducing target catch, as can sometimes occur.”

Incidental mortality of seabirds in longline fisheries has been an international conservation concern for decades, with estimates of 160,000 seabirds killed in longline fisheries annually. With 15 of 22 species threatened with extinction, albatrosses are especially vulnerable to bycatch mortality. They don’t begin breeding until they are five to 10 years of age and produce only one egg every year or every other year, Gladics said.

“Most of the mortality takes place when the birds attempt to forage on the baited hooks when fishermen deploy longlines,” she said. “In addition to the environmental impacts, there can be an economic cost as well. Losing baits to birds can be costly, and serious economic harm can occur if excessive seabird bycatch triggers a fishery closure.”

The sablefish industry in Alaska addressed the problem in part through the use of streamer lines, which are the most commonly used seabird bycatch mitigation measure worldwide. The technique runs a 300-foot line from the vessel’s mast or another high part of the vessel to a towed object like a float. A series of rubber tubes hanging down every 15 feet or so creates a visual barrier that prevents birds from attacking the bait.

However, there is a catch, the researchers discovered.

Some fishing boats use floats to keep their baits off the seafloor to conserve baits and protect their catch from damage caused by scavengers. For those that did use floats, streamer lines were less effective at preventing seabird attacks. In fact, albatross attack rates were 10 times higher on longlines with floats, compared to those without.

“Using floats puts the longline more than twice as far behind the boat before it sinks beyond the diving range of albatrosses – to the point where bird-scaring lines just don’t reach,” Gladics said. “With the hooks at the surface for longer, the birds have more time to hone in on the bait.”

Gladics said some of the West Coast sablefish boats reported that they already fished at night to prevent bird attacks and fishermen suggested that night fishing should be explored as a seabird bycatch mitigation option for the fleet.

In response, the authors examined over a decade of data collected by NOAA Fisheries at-sea observers and found that when hooks were set at night, after civil dusk, albatross bycatch was 30 times lower and target catch was almost 50 percent higher compared with daytime fishing – a classic win-win, the researchers said.

“The combination of night fishing for vessels that use floats or going without floats on the longlines and using bird-scaring lines provide two options for helping fishermen reduce bycatch,” she said. “However, a single ‘one size fits all’ solution won’t work for all fishermen and all boats, so developing multiple seabird avoidance options that are specific to the region is crucial – and that requires collaboration between researchers and fishermen.”

The research was funded by The National Fish and Wildlife Foundation, David and Lucile Packard Foundation, NOAA Fisheries, Washington Sea Grant and Oregon Sea Grant.