Gulf Restoration Network

United for a Healthy Gulf

Switching Gears to Save Bluefin Tuna

gll-bluefin-infographic-FINAL smallThe Gulf of Mexico provides important habitat for rare and beautiful marine species including Atlantic bluefin tuna, blue marlin, white marlin, sailfish, and sharks. Even before damages wrought by the BP drilling disaster, Gulf species faced a significant threat from surface longline fishing gear.

One of the major examples of the dangers of longline fishing is the population endangerment of the bluefin tuna. The bluefin tuna is a blue and silvery fish that can grow longer than 6 feet and can weigh over 550 lbs. The bluefin tuna is an active migratory swimmer that often swims across the Atlantic at depths of 500 to 1000 meters.

Unfortunately, due to high demand for bluefin tuna it’s population has dramatically declined.  We have lost 72% of the 1970 population estimate.

Part of the bluefin’s decline is due to the problem of “bycatch”, when fishermen are targeting another species but accidentally catch bluefin. By changing the type of fishing gear used, bluefin can be protected without negatively impacting catches of target species.

A decades-old problem

One of the main reasons the bluefin tuna’s numbers have crashed is due to surface longlines. This gear consists of hundreds of baited hooks suspended from lines that stretch an average of 30 miles. Surface longlines have been used commercially in the Gulf since the 1960s, and fishermen use this method to catch yellowfin tuna and swordfish.

Surface longlines have severely depleted western Atlantic bluefin tuna because these hooks catch bluefin as bycatch. Although regulations have provided partial relief for some ocean wildlife, surface longlines in the Gulf continue to incidentally catch and kill significant numbers of undersized, unwanted, and protected species. The indiscriminate and wasteful gear also catches and kills more than 80 types of non-target animals. These include endangered sea turtles and hard-fighting game fish such as blue and white marlin. Bluefin in particular face a real challenge because the Gulf of Mexico is the only known spawning area for the Western Atlantic bluefin.

bluefin tuna noaa for webAverage size of a bluefin tuna. Photo by NOAA.Picture longline gear3 for webA surface longline with its hundreds of hooks that
indiscriminately catch marine life in the Gulf.

An additional threat

In 2010, the worst offshore oil disaster in U.S. history exacerbated the negative environmental impacts of surface longlines. The oil polluted the western Atlantic bluefin tuna’s only known breeding ground and lasted through the peak of its spawning season. Millions of gallons of oil were released within a matter of months and record amounts of dispersants were used to break down the oil. The dispersants can also be a threat to the bluefin population because it can affect the development of bluefin larvae.

Though results are still inconclusive, scientists will study the impacts for years to come, but it’s clear that minimizing controllable threats to these animals will strengthen their chance for survival.

A solution

Surprisingly, the BP drilling disaster may have provided a potential solution to the problem of surface longline bycatch. Oil disaster restoration funds could help pay to transition surface longline fishermen to more selective fishing gear that could protect spawning bluefin and other ocean wildlife, while keeping fishermen in business.  Join Gulf Restoration Network in encouraging state and federal agencies to phase out surface longline fishing for yellowfin tuna and swordfish in the Gulf of Mexico in favor of more selective gear. The change to less harmful methods will halt the wasteful killing of non-target marine life such as bluefin and sailfish, and maintain fishermen’s access to yellowfin tuna and swordfish.


We have a narrow opportunity to make a significant difference for the future of Gulf fish and bluefin tuna, as well as the long-term sustainability of the communities which rely on them economically.  The Highly Migratory Species Division of the National Marine Fisheries Service is considering amendments to protect the bluefin, including baning longline gear in the Gulf of Mexico and transitioning to more selective gear.