Threats to whales

In May 1994 the International Whaling Commission, by a vote of 23 to one, established the Southern Ocean Whale Sanctuary. The sanctuary covers over 11 million square miles of ocean including all of New Zealand's exclusive economic zone south of 40 degrees south.

All baleen whales within the Southern Ocean Whale Sanctuary are fully protected from commercial whaling. Japan, as the sole objector to the decision, is not bound by it. Added to the Indian Ocean Sanctuary, established by the IWC in 1979, almost one-third of the world's oceans are now a whale sanctuary. However, despite these measures, whales remain at risk from a range of factors.

Stranded minke whale

Commercial hunting has reduced populations of most, if not all the large whales to critical levels. Only the small minke whale (six to seven metres long and weighing five to seven tonnes) is still relatively abundant. Without sufficient information on populations, continued harvesting could cause the extinction of some species.

Of an estimated quarter of a million blue whales, less than 2,000 are estimated to remain. Fin whales are less than five percent and humpback and sei whales 10 to 20 percent of their previous abundance. Of an estimated 60,000 southern right whales, only a few thousand remain. Around 150 breed on New Zealand's subantarctic Campbell and Auckland Islands.

Pollution - exposure to chronic pollutants can have a devastating impact on the health and fertility of marine mammals. In particular, concern is now focused on organochlorines, such as PCBs, once widely used in industry. An estimated 65% of the total volume of PCBs ever produced world-wide are still in use, in storage, or have been deposited into landfills. Currently some 20% have made their way into oceans. These pollutants concentrate in fatty tissue such as blubber and milk. Females transfer them in large quantities to their young when suckling.

The World Health Organisation standard classifies any material with a PCB level of 50 parts per million (ppm) as highly toxic waste. Levels of organochlorines found in marine mammals in some parts of the world far exceed this level.

Toxic algal blooms - while these occur naturally they are also thought to be stimulated by factors such as pollution, population growth, changing weather patterns and dredging of the ocean floor. Many `red tide' algae produce phyto-toxins, which can be amongst the most potent natural poisons in the world. Red tides have caused mass mortality of whales and dolphins in the USA and Europe.

Ozone depletion - Since the discovery of the ozone hole over Antarctica, concern has been raised over the effect of increased UV-B radiation. Even small increases could result in major changes to the marine ecosystem.

Global warming could affect marine mamals by impacting on the food chain and therefore their food supply.

Whale watching

Whale watching is an expanding tourist industry grossing over $700 million world-wide. In New Zealand, a tourism industry is based on regular visits of sperm and other whale species to the deep waters off the coast of Kaikoura.

Whale watching provides opportunities for education and furthering scientific knowledge. However, the rapid growth of the industry is raising concerns over possible impacts on the behaviour, migration and breeding of whales. The number of whale watching vessels around whales may disturb their normal activity. Physical harm can also be inflicted by collisions and cuts from propellers.

Regulations are necessary to provide adequate safeguards for whales from whale watching vessels. New Zealand's Marine Mammals Protection Regulations are recognised as a world leader in this area.

Cultural value

The migration legends of many tribes feature whales, considered a `chiefly fish' by Maori, a symbol of bounty. Stranded whales produced food and highly prized whale bone, and sperm whale teeth were used to make weapons, implements and ornaments. Whales remain of high cultural value to Maori. The Department of Conservation consults with iwi over the recovery of whale remains, for cultural purposes.

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