Destructive fishing techniques

Destructive fishing techniques

“Killed alongside the skipjack tuna that finds itself in your tin is almost the entire cast list of Finding Nemo.” – Author Charles Clover.

Not only do commercial tuna fishers catch too many tuna; they’re also using fishing techniques that are wreaking havoc on our oceans. 

There is one particularly nasty duo you should know about…

Purse seine fishing

Purse seining involves setting a large circular ‘wall’ of net around fish, then ‘pursing’ the bottom together to capture them. This method is common when catching fish that school together (like tuna). Although non-target fish do sometimes get caught, bycatch is very low when purse seining is used alone. 

But when you add fish aggregation devices (FADs) to the mix, it gets ugly.

60 percent of canned tuna worldwide is caught using purse seine nets in conjunction with FADs.

Fish Aggregating Devices (FADs)

FADs are man-made floating objects used to attract fish. They can be anything from old logs and bamboo rafts through to complex devices equipped with satellite-linked sonar. Fish congregate around floating objects, so FADs act like a magnet. 

So what’s wrong with FADs? 

FADs make a mockery of fishing vessel limits. They’re a sneaky way to get around agreements that limit the number of tuna fishing vessels. Who needs more vessels when you can put out hundreds of FADs to gather the tuna for you? 

FADs wreck the marine environment. Sharks and turtles get tangled in the old nets and ropes hanging below FADs. Setting nets on FADs catches and kills 2.8 to 6.7 times more non-target species (sharks, trigger fish, rays, and even turtles). Meanwhile the majority of tuna caught are juveniles. FADs then become marine junk, frequently washing up on beaches or getting tangled on coral reefs. 

Coastal fishermen sometimes use anchored FADs in conjunction with more selective fishing methods such as pole and line or handline, and that’s fine, but the use of drifting FADs with purse seiners has to stop.
The good news is consumers, industry leaders, retailers and more progressive suppliers have started demanding a move away from FADs


Right up there with the nasty FAD-purse seine combination is longlining. Longlining is used to catch the bigger, more valuable tuna, and it’s one of the most scandalous fishing methods on the planet.

Here’s how longlining works: a fishing line up to 170 km/105 miles long and covered with thousands of baited hooks is strung out from the vessel to lure and catch tuna. The problem is marlins, sharks, seabirds, turtles and other species also get caught on the line. Every year 300,000 sea turtles and at least 160,000 sea birds die like this. There are proven ways to minimise these numbers, but they’re rarely used properly, if at all.

People can work in deplorable conditions on longline vessels. In some cases they’re made to remain at sea for months or even years, working long hours for next to nothing. 

Longline fishers often transfer their catches at sea, rather than taking them to port, using a highly dodgy process known as “transhipping”. This enables large amounts of illegal caught fish to be snuck into our supply chains.

The longline industry needs a complete overhaul. It’s imperative that it is better controlled and properly managed.

For more on longlining, check out our “Out of Line” report, or for tips on avoiding longline-caught tuna, see our tuna ranking guides.