Nets’ true toll beyond reach

Press, 2 June 1989, Page 10

Nets’ true toll beyond reach

By

OLIVER RIDDELL

in Wellington

The true by-catch of small whales, dolphins and porpoises from “wall of death” drift gill nets will never be known, according to the Conservation Department.

Mr Mike Donoghue of the department said it was certain that wherever the drift-net fleets went they left thousands of dead cetaceans in their wake.

Belatedly, several nations were coming to understand the damage these nets had caused.

Because the fleets’ nets were deployed many hundreds or even

thousands of miles from shore, few but the crews had ever seen the damage inflicted on marine ecosystems, he said.

The oceanic drift-net had been developed by the Food and Agriculture Organisation under United Nations sponsorship after World War II to provide additional sources of protein. The development of a lightweight, strong and cheap monofilament nylon led to rapid growth in the use of oceanic nets, which were set each evening to drift through the upper layers of the open ocean at night and be retrieved next day.

Mr Donoghue said the nets usually fished the top 10m to 15m of ocean.

Most production in the deep tropical and sub-tropical oceans occurred near the surface, where the prize tuna and other valuable fish species were found at night. It was also where small cetaceans swam.

Monofilament nylon was so thin that it appeared to be undetectable to cetacean sonar, and so fine was the mesh it would be invisible to the dolphin’s eye, he said. From their introduction in the 19605, the nets had exacted a

heavy toll on seabirds, turtles and marine mammals, as well as non-target fish species.

The cheapness and ready availability of plastic monofilament net had revolutionised the distant-water fleets of Taiwan, South Korea and Japan, he said.

Early attempts to introduce drift-nets into New Zealand waters had been short-lived. Four Taiwanese drift-netters did exploratory fishing for squid in Golden Bay in 1981. The trials came to an abrupt end when Fisheries officers found frozen dolphin and pilot whale remains on board.