Innovative Solutions: Reducing Unwanted Catch in Tuna and Swordfish Fisheries

In early 2012, scientists at the Florida-based Nova Southeastern University Oceanographic Center began collaborating with tuna and swordfish fishermen to see if they could finally solve a problem facing their fisheries for decades – The catch of too many unwanted species. The scientist recruited several fishermen in the region to try out selective, environmentally friendly fishing gears as potential alternatives to the currently used surface longlines.

Picture of a surface longline (via United Nations Fisheries and Aquaculture Department) used to catch tuna and swordfish.

What is the problem with surface longlines? They consist of a main line that can stretch for 30 miles across the sea (or 528 football fields) and contain around 750 hooks. So, not surprisingly these longlines not only catch the desired tuna and swordfish species, but catch and kill many other species too – up to 80 different species in the Gulf of Mexico, including endangered sea turtles, the severely depleted Atlantic bluefin tuna, sharks, marlins, and sailfish. Often times, they catch just as many unwanted species as the desired species!


This fishing method even wastes the desired species. Many of the Swordfish caught on the longlines are too small to keep. So they are thrown back to sea, and the majority die.

But now more efficient and less wasteful methods may be available. Fishermen in the Gulf of Mexico have been testing out the use of “greenstick gear” and “swordfish buoy gear”.  These gears have considerably fewer hooks compared to the surface longlines and do not stretch as far across the ocean. The “greenstick” is a large fiberglass pole (which is green – hence the name) with a 500-800 ft. fishing line with 10 squid lures to attract tuna species. And the swordfish buoy gear is simply a free-floating buoy attached to a fishing line with two hooks. Fishermen may fish 12-15 of these buoy lines at one time. Both of these fishing methods allow for the gear to be quickly pulled in once a fish is hooked, reducing the chance of any unwanted catch dying.


Schematics of greenstick gear (left) and swordfish buoy gear (right) via the Pew Environment Group www.PewEnvironment.

Scientists recording catches by fishermen using these gears have found that they catch much fewer unwanted species compared to surface longlines. So far, around 90% of the catch has been made up of the desired tuna or swordfish species, while only 10% of other species. And the buoy gear appears more efficient at catching swordfish than the longline gear.  For every 1000 hooks fished with the buoy gear, 97 swordfish large enough to be kept were caught. When fishing with surface longlines, only 3 swordfish for every 1000 hooks fished are kept!

And the best news – so far scientists have recorded zero catches of sea turtles or bluefin tunas with these gears!

The testing period for the use of greenstick and swordfish buoy will end in May 2013. If the results continue to show that this gear is efficient at catching the desired species while minimizing the catch of unwanted species, we could see a major change in the Gulf of Mexico. The plan is to use restoration funds from the Gulf of Mexico oil spill to help fishermen make the switch from longline gear to the alternative gears.  If this occurs, this would be a win for conservationists, fishermen, seafood buyers, consumers, and most importantly for ocean wildlife!

And who knows, maybe tuna and swordfish fishermen in other regions would switch to more environmental friendly gears too.

This shows that there are innovative solutions out there that can improve our fisheries. And that scientists and fishermen can work together to solve the problems we face.

Please visit the Pew Environment Group website to learn more about this project.


Elizabeth Brown is a research scientist at Blue Ocean Institute.

2 Comments on “Innovative Solutions: Reducing Unwanted Catch in Tuna and Swordfish Fisheries

  1. Wow! One of the best and clearest summary if the issue I have seen! Bravo!

    • Thank you for your interest and the nice comment! I encourage you to explore more ocean issues on our website, especially those under “Fish as Food.”

  2. Pingback: The Impact of the Global Fishing Industry – MeganCheckers

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