Starting May 5, commercial fishermen using longlines that stretch for miles in the Gulf of Mexico must use hooks designed to straighten when grabbed by bluefin tuna, releasing the fish.

Three years of tests have shown that these “weak hooks” will hold most yellowfin tuna, swordfish, and other commercial species while cutting the accidental bluefin catch by 56 percent, the National Oceanic and Atmospheric Administration said Friday.

That could cut the number of bluefin caught from an average of 285 a year to 124 bluefin caught this year, it said. Although fish still alive when they reach the deck are released, many die from the stress of being caught and hauled to the boat, according to NOAA. The lines are 10 to 20 miles long, NMFS fishery management specialist Randy Blankinship said.

Requiring weak hooks is a good step but not enough, said Catherine Kilduff, an attorney for the Center for Biological Diversity. The center asked NMFS last May to declare bluefin endangered, saying the Gulf of Mexico oil spill had depleted their numbers. The agency must decide that question by May 24.

“That’s where we’re putting most of our energy,” Kilduff said.

It’s important to get the hooks in use this spring because bluefin spawned in 2003 will soon be old enough to spawn, Blankinship said. He said data indicate this is the largest “year’s class” since 1974, and numbers born since have been quite low, so protecting these fish can help long-term rebuilding.

Fishermen who haven’t already adopted the hooks — NOAA quoted Capt. Mike Carden of Panama City, who participated in its research, as saying he and several fishermen he knows already have done so — will have to change them all by May 5. The National Fish and Wildlife Foundation is offering vouchers to help pay for the new hooks, Blankinship said.

It’s illegal to fish for bluefin tuna in the Gulf of Mexico, the only known spawning area for western Atlantic bluefin. Part of an internationally set U.S. quota is used to cover bluefin caught accidentally by commercial boats trying to catch other kinds of fish.

Kilduff said that should be made a hard quota that ends the longline commercial season once it’s reached. 

The new hooks are the size and shape required since 2004 to protect sea turtles, but made out of slightly narrower wire.

NOAA said yellowfin tuna caught in the Gulf average 86 pounds, while the accidentally caught bluefin average 485. Even bluefin the same size as fish the boats are targeting might be able to get free of the hooks, Blankinship said: “It’s not weight — it’s how hard the fish is swimming and the power and force it exerts.”

Or, as Kilduff put it, “Bluefin tuna are just machines. They’re built for power and speed. So they say — though they haven’t done a lot of research on weak hooks — that bluefin tuna have a burst of energy that might allow them to get off the weak hook.”

Bluefin begin spawning in the northern Gulf of Mexico in April — the month BP PLC’s undersea well began spewing millions of gallons of oil last year — and continue through June. By that time last year, more than one-third of federal waters were closed to fishing because of oil. The only other place bluefin are believed to spawn is the Mediterranean Sea.

The European Space Agency and nonprofit Ocean Foundation, comparing bluefin spawning areas to satellite photographs of the spill, estimated in October that the spill killed one-fifth of the eggs and larvae.

The Center for Biological Diversity and other environmental groups say bluefin had been headed for extinction long before the rig operated by BP PLC exploded on April 20, 2010, largely because of the premium sushi market. On Jan. 5, a 754-pound tuna sold for nearly $396,000 at an auction in Tokyo. But other researchers say the species is in good shape.

Bluefin is an important fishery in New England, where people blame European overfishing for any declines.

The International Commission for the Conservation of Atlantic Tunas cut bluefin quotas in November, but rejected proposals to suspend fishing for bluefin entirely.

Online:

http://www.nmfs.noaa.gov

http://www.nfwf.org

http://www.biologicaldiversity.org

http://www.esa.int/esaCP/SEM1K4WO1FG—index—0.html