A large number of marine animals end up as bycatch. Could smarter nets make a difference?

Daniel Stepputtis’ face fell as his crew lifted their trawl net out of the grey waters of the Baltic and over the side of the boat. Like a yeti emerging from the sea, thick red algae clogged every hole in the specially-designed net’s mesh.

On this cloudy day in the middle of July, the algae – or ‘Kraut’ as the fishermen call it – was blooming.

“That’s it for today,” Stepputtis, a fisheries biologist, declared as his colleagues began the tedious task of cleaning the tangled mess.

Dr. Daniel Stepputtis of the Thünen Institute stands on the deck of the research vessel, the Clupea. (Credit: Gerhard Westrich)

Researchers watch as the Thünen Institute’s FLEX net is hauled onboard. (Credit: Gerhard Westrich)

Wearing orange plastic overalls and helmets to protect against cold water and heavy onboard machinery, researchers aboard the Clupea emptied their small catch into a large container. Muddy cod and flatfish of all sizes came tumbling out of the net, but the scientists from the Thünen Institute of Baltic Sea Fisheries couldn’t hide their disappointment. They would have no choice but to repeat their work in the months ahead.

Stepputtis’ research team has been testing the effectiveness of FLEX nets, a new fishing net prototype that aims to reduce bycatch, or animals that are unintentionally caught by fishermen. Conducting research on the open water where weather and currents are always in flux, however, is challenging and often unpredictable.

Fortunately, the Baltic Sea cod fishing season takes place mainly during the winter, when algae is less likely to bloom and researchers can focus on other problems clogging fishing nets. Flukes, plaices and other species of flatfish that live on the ground also get pulled in by fishermen. After the trawls are emptied, the fisherman throw these species back into the sea, a procedure many don’t survive.

Thünen Institute researcher Bernd Mieske sorts through the catch from the FLEX net. (Credit: Gerhard Westrich)

A mix of flatfish and cod are caught in the FLEX net. Researchers are attempting to reduce global fishing bycatch by using specially adapted nets. (Credit: Gerhard Westrich)

In his narrow office crammed with paperwork and books, Daniel Stepputtis is working on solutions to this problem. A tall blonde scientist sporting a goatee, Stepputtis is in charge of the working group for survey and fishing technology at the Thünen Institute of Baltic Sea Fisheries – a sleek modern structure located right at the old harbor of Rostock, Germany.

His team is working to address one simple question: “If you don’t want to catch [the fish], how can you get them out [of the net]?” Unfortunately, the answers are complex and different for each fishery.

“It’s not only in the Baltic that different species end up in the trawls, but all around the world,” Stepputtis explains. This bycatch poses a problem not only to environmentalists, but also to fishermen who have to drag additional, unprofitable weight through the water and meticulously sort through the catch, which costs them time, energy, and money. And they know that a lot of what they throw back later dies.

In response to this problem, Swedish fisherman Vilnis Ulups began to experiment with the idea of building “emergency exits” into the nets to accommodate different body morphologies of flatfish and round codfish. If one could build holes thin enough for flatfish to swim through, he thought, then their bycatch could be reduced without affecting the cod harvest.

Ulups got in touch with the experts at Thünen who liked the idea and started to refine the prototype he had built. The net featured metal bars that formed slim exits for the flatfish, however, when researchers ventured out to sea to conduct tests, it did not work.

“The fish seemed to feel uneasy, and stayed away from [the exit holes],” recalls Stepputtis. The flatfish inexplicably remained at the bottom of the nets, far from any chance at escape. To find out why, the researchers installed cameras to monitor what was happening. “We tried to put ourselves in [their] place,” Stepputtis explains.

Dr. Daniel Stepputtis (left) and Bernd Mieske mount underwater cameras on fishing nets designed to reduce bycatch. (Credit: Gerhard Westrich)

View of the Baltic Sea from the research vessel Clupea. (Credit: Gerhard Westrich)

So, how could the scientists help the flatfish find their emergency exits?

The answer turned out to be quite simple. Just like traffic islands divert streams of cars and bikes, a similar structure could direct the flatfish toward the holes in the nets. Using the underwater cameras to monitor the adapted net, Stepputtis and his team saw fish turning to avoid the obstacle, which led them toward the holes and ultimately, freedom. The concept was viable.

Tests have shown that this early prototype, known as the FRESWIND – short for Flatfish Rigid Escape Windows – was able to significantly reduce flatfish bycatch by up to 60 percent. Less flatfish clogging the nets means that juvenile cod can also escape and reproduce, which helps to stabilize the population. The overall reductions in bycatch were so substantial that the World Wildlife Fund (WWF) named the FRESWIND net as one of the runners-up in their Smart Gear Competition in 2014.

Side by side comparison of the FRESWIND (left) and FLEX net prototypes

“[Bycatch] is a major issue in fisheries all around the globe,” explains Mike Osmond, who runs the WWF’s international contest. “The amount is astronomical.”

And it’s not only fish. Numerous other species from benthic invertebrates to turtles, whales, and sea birds are also affected by equipment deployed by the global fishing industry.

According to a WWF estimate, over 40 percent of the global catch is bycatch – a truly staggering, but much disputed number. Christopher Zimmermann, who heads the Thünen Institute of Baltic Sea Fisheries, says that WWF deliberately widened its definition of bycatch to make the situation “as dramatic as possible.” While it remains a major problem that must be addressed to reduce human impact on the seas, he believes that only around 7 percent of the global fish catch can actually be considered bycatch.

The rest, Thünen researchers say, is “unwanted catch” – fish that can still be sold by fisherman at the port or brought home for dinner – but the authors of the WWF study criticize this as a definition that’s too narrow to grasp the problem. It’s not only a dispute over the right definition of bycatch that makes it hard to actually come up with numbers.

“The magnitude […] is really very hard to quantify,” says Kim Detloff, who heads the Marine Conservation section at the Nature and Biodiversity Conservation Union (NABU), a German environmental NGO. “In the past,” he says, “you could only estimate how much unwanted fish went overboard.”

The Thünen Institute’s FLEX prototype is hauled onboard. Researchers hope the prototype will reduce the number of flatfish caught in the nets of Baltic Sea fishermen. (Credit: Gerhard Westrich)

But no matter what proportion of global catch, bycatch remains a major environmental problem that kills a massive amount of sea life each year. It’s an issue that scientists and fishermen alike are looking to tackle.

Decades ago, nobody worried about catching a little extra in the net. The oceans were a vast, endless supply of fish and other seafood. “For a long time, the meshes were so small, everything was caught,” remembers Gerd Junge, a 64-year-old fisherman who has worked in the industry for half a century. He recalls going out with huge trawlers that brought in everything from juveniles to adults. Within just ten years, the boats had taken out the entire codfish population off the coast of Canada.

“Then in the late 60s, early 70s, minimum mesh openings were introduced to let the small fish escape,” recalls Junge – a first step towards more sustainable fishing practices. At that point, however, the changes were only made to allow juvenile codfish to evade capture and reproduce. The nets weren’t smart enough yet to distinguish between species.

As a child, Junge had watched the fishermen knit and repair their nets on the beach, fascinated by their craft. He studied fishing technology and started to work at Kloska GmbH in Rostock, a company that produces nets for fishing boats all over the world. He is now their head of production.

Within the quiet, spacious production hall, young men in blue overalls knit and repair meters and meters of nets in swift rhythm. Here, the prototype for the Thünen Institute’s award-winning net for multi-species selection was produced.

Workers at Kloska GmbH prepare fishing nets. (Credit: Gerhard Westrich)

(Credit: Gerhard Westrich)

“I think it’s the right approach to sort different fish species within the net,” says Junge, who admits that the FRESWIND net’s higher price tag presents obstacles to greater industry use. “The fishermen will start to use them only if there is a legal basis, if it’s the law,” he says, “before that, there won’t be a market.” Economic pressure and legal regulations drive what happens in the fishing industry. A new net is a huge investment, especially for those working on a local scale.

Some of the other smart gear promoted by the WWF’s Smart Gear Competition sound like something out of a science fiction movie. The 2009 runner-up, HOVERCRAN, proposed reducing bycatch and seafloor damage by using low-intensity electrical pulses to startle shrimp up into a hovering trawl. Other proposals have outlined plans to deter sharks with magnets, scare birds away with lasers, and use foul-smelling pellets to keep sharks off of longline hooks.

Despite the economic stresses of the industry, some fishermen are pushing for change by developing their own new innovative concepts. Mike Osmond, who runs the competition, estimates that “70 percent of the winning ideas have come from fishermen.”

One of them is Kazuhiro Yamazaki, the captain of a Japanese tuna vessel, who brought home the prize in 2011 with a simple idea. He proposed protecting seabirds who often chase bait thrown out with longlines by using a double-weight branchline to increase their sinking rate. The crucial point of the design was to make it safe enough for fishermen to use without injury.

“One of the things I realized about the competition is that technology doesn’t have to be complex,” says Osmond. But he also stresses the importance of economic factors in order to get the new gear on the market and into practice. “A lot of developing countries […] can’t afford to implement or utilize new technologies that come along,” he explains, “until the technology can be made really cost-effective.”

Some of the winning ideas from the Smart Gear Competition have moved beyond the pilot stage, and are now used more widely in practice. Such is the case for the SeaQualizer, a small device attached to the end of the line to avoid barotrauma in recreational sports fishing. When fish are pulled up from the depths, their lung bladder can inflate, which prevents them from swimming back down when released. Initially developed for red snappers in the Gulf of Mexico, the recompression device is now used along the U.S. Pacific coast.

The Smart Gear competition has also provided new technology to reduce the bycatch of larger animals, such as turtles and whales. In 2005, a team from Canada and the U.S. handed in a concept for altering the chemical properties of gillnets, so that cetaceans such as whales or dolphins could better detect and even break them.

Gillnets are very thin, long walls of fishing net that are hung along the water column over long stretches. When fish swim through the mesh, they can pass until their gills are through, but then get stuck. Cetaceans who get caught in them are unable to go back to the surface to breathe and often drown.

In the Baltic Sea, the majority of fishermen use gillnets. “It’s a little known fact that we have a whale species here as well, off the North Sea and Baltic coasts – the porpoise,” Kim Detloff of NABU points out. The porpoise is a small mammal, with a dark body, white belly, and very small back fluke. Of the two populations found in the Baltic Sea, one is critically endangered. With only about 450 individuals left, Detloff says gillnets are their number one cause of death.

To prevent cetaceans from getting caught in gillnets, experts have also proposed the use of pingers, which send out signals to deter the whales. But under certain circumstances, these pingers have shown to lead to higher rather than lower whale mortality rates. The PAL, short for porpoise alarm, is a new kind of pinger that imitates actual whale clicks and is favored by some as a better solution. But to Kim Detloff, this remains less than optimal as it drives the porpoises out of areas where they feed and reproduce.

The risk of bycatch in gillnets isn’t limited to whales, dolphins, or porpoises. Gillnets also pose a threat to seabirds, who get tangled in the net when diving for food. Since seabirds and whales rely on different senses – seabirds are more focused on sight, while whales on hearing – it is hard to find a solution to protect both groups of animals.

“It’s a long way to go until we have developed a gillnet that can prevent bycatch of whales as well as seabirds,” Kim Detloff says. A shift to other fishing methods might have better effects. Rather than equipping the gillnets with fancy technology to scare off animals, longlines or fish traps could be used. Traditional methods that have been long been phased out or forgotten could be rediscovered and adapted.

However, Detloff believes no single alternative will be able to replace gillnets completely. Policy will have to play a role, he says, to make sure that certain areas important to the whales and other protected animals are exempt from gillnet fishing.

Researchers are attempting to reduce the number of flatfish unintentionally caught by Baltic Seas fishermen. (Credit: Gerhard Westrich)

Bycatch is a complex problem with no single solution. In every type of fishery and with every technology used, the problem looks different. There is no silver bullet, short of bringing the entire fishing industry to a halt – which would threaten the food security of an estimated billion people around the world. But understanding the behavior and communication of each animal threatened is crucial to developing solutions for each type of fishery.

For the Baltic Sea, new rules are finally starting to make a difference. Since the beginning of 2015, the European Union has begun to enforce a new discard ban, which demands fishermen be held accountable for everything caught in their nets, not just the catch they want to sell. Unwanted bycatch has to be counted against the quota that fishermen are allowed to fish for, effectively reducing their commercial catch.

Fishermen in the region have been vocal in their opposition to this new law, but Zimmermann of the Thünen Institute hopes that this could incentivize fishermen to upgrade their gear.

In the future, new technologies to prevent bycatch could include digital imagery and livestreams directly from the net. Instead of fishing in the dark, cameras could enable fishermen to evaluate the species and size of fish in the net before hauling the catch aboard.

Thünen Institute researchers haul their adapted FLEX net overboard. (Credit: Gerhard Westrich)

The FLEX net spreads out behind the research vessel, Culpea. (Credit: Gerhard Westrich)

For now, the Thünen researchers are using cameras to optimize their smart nets and take small, but important steps to reduce the side effects of fishing on the marine ecosystem – in an ecologically as well as economically sustainable sense. “Only if both come together, we will have a fishing industry that can feed us in the long term – one that we can accept,” explains Stepputtis.

So as soon as the algae is gone, Stepputtis and his team will go back out to sea to test FLEX, their latest prototype – a trawl net with a wide-open window and a little ramp, letting flatfish elegantly slide down to freedom.