Quick Dips

Ghost Fishing Substantial

Not all fish caught by commercial fishing gear end up in the boat. Ghost fishing, the capture of fish and other creatures by lost fishing equipment, is a worldwide problem economically and environmentally.

Findings from a global survey conducted by MAF Fisheries scientist Paul Breen were presented at a recent international conference on marine debris.

Lost gear that continues to catch fish costs the industry millions of dollars a year around the world. Breen discovered that the very large amounts of fishing gear used translate to a large amount of lost equipment, even if the rate of loss is small. Few estimates of driftnet loss are available, but it may reach as much as 2,500 km a year in the Japanese North Pacific squid and salmon gillnet fisheries. One 3.5-km pelagic gillnet lost for at least a month was found containing 99 birds and 78 fish.

"Live birds appeared to be attracted to the net, perhaps by the material already caught, and many of the fish were fresh," Breen notes.

In a local study, fish were caught even when gillnets were partly wrapped up and covered in seaweed. Rock lobsters attracted by the fish also became entangled. Lost salmon gillnets in Washington have continued to catch crabs, fishes and birds for at least 3 years. Even such unlikely animals as reindeer have been caught.

Ghost fishing by pots or traps used for catching crustaceans is also a problem. In some cases, other species may enter the trap and end up acting as fresh bait for the intended quarry. Live animals in a trap may attract others of their own kind.

Many animals can escape, so that entering a trap may not be the end of them. Some are better at it than others: New Zealand rock lobsters have a rapid turnover rate in traditional crayfish pots, but Hawaiian spiny lobsters seem less adept at escaping.

Few estimates of the actual cost of ghost fishing are available, but the problem is clearly not minor. In one US lobster fishery, about 20-30% of all traps used each year are lost, with a catch loss estimated at 670 tonnes worth US$2.5 million.

There appears to be no easy and practicable way of preventing gillnet ghost fishing. One possibility is using natural fibre to attach the mesh to the cork line. Eventually the fibre will decay and the net come apart. However, Breen sees this as a backward step because of the massive effort that would be required to maintain and preserve nets during fishing.

Mike Bradstock