January 15, 2013


Japanese Fishery Meets Challenge to Reduce Bycatch from World's Oceans (Part One)

Keywords: Ecosystems / Biodiversity Food Newsletter 

JFS Newsletter No.124 (December 2012)

The World Wide Fund for Nature (WWF), one of the world's largest conservation organizations, was set up to protect endangered wildlife. One of its activities is to host the International Smart Gear Competition to promote fishing gear that helps protect marine life. In 2011, a Japanese fishery group won this competition's grand prize.

Through the courtesy of WWF Japan, we will present an interview about this group's inventive approaches and fishing gear development in our newsletter over the next two months.


The International Smart Gear Competition hosted by WWF is a contest for judging fishing gear that has been designed to reduce threats to ocean life. The grand prize winner of the competition in November 2011 was a "double-weight branchline" invented by the Japan Tuna Fisheries Cooperative Association. This gear is attracting attention as a new way to reduce bycatch in the tuna longline fishery; in particular it reduces the incidental catch of seabirds. We interviewed a member of the Association about the process of developing the double-weight branchline, which ensures the safety of both fishermen and seabirds.

Interview: "Our wish: Swift Worldwide Dissemination of Double Weight Branchline Fishing Gear"

In fisheries, unintentionally catching non-targeted species in nets or with hooks, called "bycatch," is a problem throughout the world in various types of fisheries.

For example, bycatch of seabirds such as albatrosses and petrels has been a problem in pelagic tuna longline fisheries for many years.

However, an improved fishing device - the double-weight branchline - significantly reduces seabird bycatch and won the grand prize in the International Smart Gear Competition hosted by WWF in November 2011. This device can be an effective solution to the seabird bycatch problem.

The following is an interview with a member of the Japan Tuna Fisheries Cooperative Association about this prize-winning fishing gear.

Longline Fisheries and the Seabird Bycatch Problem

Q: First, could you tell us about longline fishing?

A: Longline fishing is one of the methods used in pelagic fisheries. It consists of a main long line to which many branchlines are attached. Each branchline has a baited hook at the far end for catching tuna or skipjack. The main line is about 150 kilometers in length and carries about 3,000 branchlines.

Q: Are seabirds are caught on the branchline hooks?

A: Yes, they are. Petrels sometimes dive into the sea trying to grab the bait fish attached to the branchline hook and can get caught on the hook.

When petrels get a bait fish come up to the surface, albatrosses attack them in order to steal the fish. During these fights, they sometimes get caught on the hooks and drown when they can't get to the surface.

The maximum depth petrels can dive is at most 10 meters. So, when baited branchline hooks sink below 10 meters, they no longer pose a danger to seabirds.

Baited hooks in tuna longline fishing are normally sunk to a depth of about 200 to 300 meters. In fact, the idea of putting weights on branchlines to cause them to rapidly sink down deep has long been considered a potentially effective solution to prevent seabird bycatch.

Q: That's the weighted branchline, then. What motivated you to do actual trials of this method?

A: Five years ago, we were planning to carry out fishing operations within the 200 nautical mile exclusive economic zone (EEZ) of the Republic of South Africa. This area is known to have particular large numbers of seabirds. The government of South Africa sent us an operational provision stipulating that our "annual seabird bycatch should be fewer than 25 birds."

We tried using "tori" line* and nighttime casting in part of our operations, but in the first year, 100 to 200 seabirds were caught in the longlines.

* A "tori" line or bird-scaring line, is a device developed in Japan that consists of a long pole fixed to the stern of a fishing vessel that tows a rope with colorful streamers and tape supposed to scare birds away from bait fish. It is known as a tori-line or tori-pole.

At that time, we were contacted by Professor Ed Melvin, a marine scientist at the University of Washington. We worked together with him for the three years from 2008 to 2010 to try to introduce weighted branchlines.

Double-Weight Branchlines Evolve through Further Trials

Q: The present award is for "double-weight branchlines". What does "double" refer to?

A: A weighted branchline has a 60-gram lead weight attached to the end of the line.

However, we found that when we actually used these lines at sea, when reeling in the longlines during stormy weather or when there was a big swell, the weights attached to the branchlines flew like bullets through the air towards the fishermen.

These weights tend to collide with crewmembers' heads or faces, and in fact have caused serious accidents such as sight loss or skull fractures.

Prof. Melvin came up with the idea of wrapping the weights in rubber, but this was still not effective enough to reduce accidents. It was at this time when Kazuhiro Yamazaki, captain of the fishing vessel Fukuseki Maru No 5, suggested the idea of a double-weighted branchline with two weights attached separately to the line.

Q: Did this work to stop accidents?

A: When two weights with a total weight of 60 grams are attached separately, the weights do not recoil in a straight line, and this prevented accidents involving weights hitting crewsmembers' heads.

Also, with just one weight, the baited hooks tend to get fouled when sinking down. Fouled branchlines can't catch tuna very well, and this eventually affected the entire fishery operation. Spacing the two weights apart and connecting them with a wire also reduced problems with fouling lines.

Double-Weight Branchline Results -- Bycatch Drastically Reduced to Six Birds

Q: What was the effect in terms of bycatch mitigation?

A: Nine vessels are in operation at this time, but only six cases of seabird bycatch were reported for during the beginning of the 2012 fishing season, which starts in April - May.

One vessel normally sinks about 3,000 hooks a day, which means nearly 30,000 hooks with nine vessels. Only six cases were reported during a period of one month, so I think this verifies the efficacy of the new method. Some vessels have not even caught a single bird. I think we can say that the double-weight branchline method will be able to drastically reduce bycatch incidents without lowering fishing efficiency.

Q: How did these six cases happen?

A: The branchlines are sometimes reeled in with bait fish still on the hooks. Birds dive for such baits and get caught on the hooks.

Unfortunately, we don't presently have a good way to prevent this kind of incident, but these birds are caught alive, so we release them as soon as possible.

In that sense, we can say that almost 100 percent of accidental deaths of by-caught birds was prevented.

Since ancient times, fishermen in Japan have preferred to avoid needless killing. Be it birds or turtles, fishermen basically assume that they should release any kind of bycatch-type organism caught alive.

From WWF Japan's article
Japanese Fishery's Challenge to Reduce Bycatch from World's Oceans (in Japanese)

To be continued in Part2