Date:24 August 2011
The accidental capture of marine species kills millions of fish, birds and mammals each year. It also threatens to close fisheries. Using hard-won knowledge, fishermen are redesigning gear to reduce bycatch, ensuring that every haul is the right one for the oceans and for profit. By Edward Nickens
The nets come out of the water like giant sopping drapes, 5-metre cascades of blue and green mesh dripping seaweed. The wooden decks of the Grandville Davis shudder with the weight of tautog, sea bream, flounder, butterfish and hundreds of squid jetting streams of ink and seawater. The vessel’s captain, Chris Brown, is dwarfed by the trawl. He wears the waterman’s uniform: blue jeans, a sweatshirt and a ball cap grimed with fish scales. But he’s unhappy with the catch.
“A shorter funnel might give the fish some time to think about a way out, give them more ways to escape,” Brown says. The funnel is a tube of polyethylene mesh that channels fish caught by the net into a pound at the tail of the trawl. “Let’s do a little engineering here.” He stitches large folds of the mesh together with a needle the size of a ballpoint pen. “The more fish we can keep out of the net,” he says, “the better.”
This might seem like a curious comment for a commercial fisherman to make. But here in Block Island Sound, with Rhode Island a smudge in the west, Brown is not just fishing for squid. He’s trawling for data and insights he can use to design squid nets that catch fewer fish, and thus help the squid industry navigate one of the thorniest issues fishermen face: the accidental capture of non-targeted species of fish, birds or marine mammals, called bycatch. Although rates vary among fishing techniques, global totals of bycatch are in the millions of tons per year.
Today, the issue vexing Brown is a high incidence of sea bream and butter- fish bycatch. By pulling an experimental net and a control net side by side 36 times over six days, Brown and a team of scientists and net-makers will test concepts for a new trawl designed to catch squid but make it easy for fish to escape. The old paradigm for commercial fishermen is the hunting paradigm: burn fuel and find fish,” Brown says. “But I want to be a harvester, not a hunter. I want a degree of certainty that I will catch fish. That means the fisheries have to be healthy"
Bycatch has a staggering effect on many species. In the Gulf of Mexico, an average of 4 kilograms of fish – redfish, sea trout, flounder – and crab are caught for every kilogram of shrimp sold; most of that bycatch is discarded. Tuna and swordfish longlines set in the ocean can be 60 kilometres long and carry thousands of baited hooks; they kill enormous numbers of dolphin, sea turtles, sharks and seabirds. Migrating loons and red-breasted mergansers drown in nets set to catch flounder along the mid-Atlantic coast. Maine lobstermen struggle to keep their pot lines from entangling endangered Northern right whales. And all six species of sea turtles found in US waters are vulnerable to fishing equipment.
Marine life isn’t the only thing bycatch affects; it can also sink a fisherman’s bottom line. Accidental entanglement costs time and money, and the bycatch of some endangered species can cause regulators to idle boats and shut down entire fisheries. That’s why the World Wildlife Fund has attracted a growing number of fishermen to its International Smart Gear Competition, where they’ve used their experience to develop new equipment – from magnetladen lines that repel sharks to trawls with escape hatches that allow sea turtles to pass safely through. For sea turtles alone, the stakes are enormous: Between 1990 and 2008, experts estimate sea turtle bycatch losses of up to 8,5 million.
“There is fabulous innovation going on between commercial fishermen, agencies and non-governmental organisations in a global push to reduce bycatch,” says Ed Cassano, founder of Integrated Marine Education and Research Expeditions in Monterey, California. “The knowledge fishermen bring to the table about gear efficiencies and fish behaviour is irreplaceable.”
By exploiting how fish species respond to trawls, nets and lines, fishing gear can be fine-tuned to separate its catches. Modifications can be simple: in the ’90s, about 16 000 seabirds such as petrels and albatrosses died each year in longlines set in Alaskan waters for sablefish, Pacific cod and turbot. In the nine years since fishermen began attaching brightly coloured streamers to the lines, seabird deaths have dropped 70 per cent. Other bycatch-reduction methods are more technical. The Passive Porpoise Deterrent increases the “acoustic visibility” of gill nets, helping marine mammals avoid entanglement. When a porpoise emits a click, resonant acoustic reflectors affixed to a net every 5 metres send an echo much bigger than the cetacean’s largest prey. A small number of active pingers alert porpoises to the nets when they’re not using echolocation.
Some technologies are a mix of MythBusters, high school handwork class and advanced engineering. One is the Eliminator. When haddock encounter a net, they tend to swim upward, whereas cod and other fish head for the bottom. By designing a net with larger mesh openings near the rockhopper – the part of the trawl that drags on the seabed – the Eliminator traps haddock while allowing other fish to escape. The result: an 81 per cent reduction in cod bycatch and a 95 per cent reduction in flounder bycatch, with little impact on haddock catches.
Fine-tuning fishing gear requires more than trial and error on a boat, however. On the concrete floor of a former clam- and fish-processing factory just metres from where Brown docks his trawler, Jon Knight uses a pushrod and fid to weave one polyethylene rope through the braids of another, splicing a reinforced rope eye into part of the Eliminator. Knight is the owner of Superior Trawl, and it’s his job to turn ideas for gear into elaborately woven webs of mesh and heavy weights. “Making something real out of someone’s vision,” he says, “that’s where the fun is.”
Knight worked on the design team for the Eliminator, and he is helping Brown on the squid trawl project – a partnership between Knight, Brown, his fishing partner Steve Arnold and the Rhode Island Sea Grant organisation. It has involved not only tests in the open sea, but hours of computer-aided design. The team even made a trip to Canada to run a scale model of the squid trawl through a 22-metre fume tank at the Fisheries and Marine Institute of Memorial University of Newfoundland. Watching in real time, the trawl designers could see how various haul speeds a. ected the experimental net’s elongated funnel.
“Whatever solutions we come up with have to work out on the water,” says David Beutel, aquaculture co-ordinator at the Rhode Island Coastal Resources Management Council. “For fishermen, there is a growing environmental-stewardship aspect to this work. But it’s still driven by their need for efficiency. You make the most money when you are most e. cient.”
Such resourcefulness requires change. In fact, this is the last voyage for the Grandville Davis, a mahogany-hulled work boat Brown built 32 years ago. He has bought a new glass fibre boat whose light weight and shrouded propeller can tease out efficiencies for a more modern way of fishing. After more than a quarter-century of the Davis catching as much as possible, its last hurrah is helping the global fishing industry move toward a sustainable future.
“Every dollar I’ve ever made in my life, I’ve made on this boat,” Brown says, working the levers that drop the trawl for another experimental tow. “I’ll miss her, but things are changing. Society’s willingness to support commercial fishing is directly correlated to our ability to prove that we can take care of a national resource. That was not a part of our language five years ago.”
Nothing but net
Bycatch, the accidental capture of marine life, endangers species and undermines fisheries. But new trawls exploit sh behaviour to leave bycatch behind. – Olivia Koski
1. Lobster, flounder, haddock and cod enter the net.
2. Lobster, flounder and cod head down, escaping from the net’s large bottom mesh.
3. Haddock swim up into the tightly woven cod end. Fishermen experiment with mesh size to maximise good haul and minimise bycatch.
1. Bass, sea bream and squid enter the net, then swim into the funnel.
2. Bass and sea bream emerge from the funnel and escape out the sides.
3. Squid, weakened by releasing ink in the funnel, fall into the tail. Finding the funnel’s sweet spot is key: too short, and all sh are lost; too long, and all catch goes in the tail end.