An Auckland researcher who has warned that collapsing squid stocks may imperil some whale species is probing the cause of whale deaths in what he says is an exceptional number of recent strandings.
Steve O'Shea, the director of the Earth and Oceanic Sciences Research Institute at the Auckland University of
Technology, is currently investigating the death of a young calf, a Haast's beaked whale, which measured only 2m when it died at Mussel Point at Jackson Bay, south of Haast.
The species, also known as the Gray's beaked whale (Mesoplodon grayi), strands relatively often around New Zealand.
Dr O'Shea's investigation, in collaboration with other experts, will be televised on the Discovery Channel in the United States on July 14.
Before the filming, Dr O'Shea said five species of squid and octopus in New Zealand seas were classified as critically endangered, and it was important for greater knowledge to be gained about their place in ocean ecosystems.
Part of the reason this was important was the role of some species in the diet of toothed whales, such as the largest species, sperm whales and the smaller Haast's species. Forty years ago, 37 per cent of the diet of sperm whales in New Zealand waters was fish species now taken by trawlers as commercial catch, such as orange roughy, hoki, ling, rig, and southern kingfish.
By the 1990s, sperm whales were reduced to eating 100 per cent squid, with the males consuming 350 squid a day and females 750 squid.
He said 16 recent strandings on west coast Auckland beaches in recent years had involved whales which had been malnourished and disoriented, apparently because of food shortages.
Dr O'Shea said 78 of the 85 species of squid in New Zealand waters released egg masses to breed but the fragile, gelatinous eggs were being cut to ribbons by trawlers' nets.
"We are seeing the collapse of squid stocks, which are staple in the diet of the sperm whale.
"These whales are not eating anything ... there is nothing left".
This made it important to raise public awareness of squid and the impact of fishing on wider ecosystems, and the potential for marine protected areas or reserves.
- NZPA
