By Richard Black
Environment correspondent, BBC News, Madeira
Mexico's twin crises - swine flu and the economy - may derail a plan to save the world's most endangered cetacean.
Only about 150 vaquita are left, and about 30 are dying each year through becoming entangled in fishing nets.
The government has cut funding aimed at taking fishing boats out of service or adopting vaquita-friendly equipment.
The vaquita, which is also the world's smallest cetacean, is emblematic of the plight of other dolphins and porpoises around the world, say campaigners.
As government delegates, scientists, whale-hunters and environmentalists discuss the large ocean-traversing cetaceans at the International Whaling Commission (IWC) meeting here, green group WWF's new report, The Forgotten Whales, concludes that some of the leviathans' smaller brethren are more at risk.
Earlier this year the baiji or Yangtse River Dolphin was declared probably extinct, and the Critically Endangered vaquita (Phocoena sinus) - another species restricted to a small, specific habitat - will follow suit without swift action, conservationists believe.
"The estimated mortality comes to more than 30 animals per year, and having a population that is only 150 - you can imagine that the population will not survive if nothing is done," said Lorenzo Rojas-Bracho, Mexico's IWC commissioner and the head of the national marine mammal research and conservation programme.
"The situation is so critical, you can't kill more than one vaquita per year of you want to save it for future generations."
The boto - a South American river dolphin - also faces an uncertain future
After years of successive Mexican governments denying the problem, the current administration recently put $18m into a fund aimed at removing vaquita-threatening gillnets from the waters in the north of the Gulf of California, which is its only habitat.
Dr Rojas-Bracho said the programme had removed about 500 illegal fishing vessels from the area, while about 400 legal ones had taken funding either to leave the industry or to adopt other types of gear.
Another tranche of similar size had been due, he said, but had been cut by about 60% because of the country's other problems.
"Our environment minister has insisted it's a priority for the government, so we're happy with that - but it won't be easy," he told BBC News.
Other countries including Sweden and the US had contributed, he said, and the work had been supported by WWF and the International Fund for Animal Welfare (Ifaw).
But other conservation organisations that complained about the vaquita's plight had not been so quick to contribute funding, he said.
With full funding, he added, it might have been possible to bring vaquita deaths from fishing nets down to zero - which is probably needed to save the species - but now that might not be possible.
The vaquita and the baiji head a list of eight small cetaceans that WWF says are under threat.
Others include the river dolphins of the Indus and Ganges, Hector's dolphin of New Zealand, the Atlantic humpbacked dolphin that lives off the West African coast, and the boto or Amazon dolphin.
Pollution, loss of habitat and shipping are among the factors reducing their populations.
WWF points out that of 69 small cetacean species, 40 are categorised as Data Deficient by the Red List of Threatened Species, meaning there is not enough evidence to know whether their populations are declining or not.
Many environment groups would like the IWC's remit to include conservation of these small cetaceans.
"It is time for the IWC and its members to take full responsibility for the conservation future of all whales great and small," said Heather Sohl, species policy officer with WWF UK.