By Richard Black
Environment Correspondent, BBC News website
The United Nations says additional protection measures are needed for dolphins and small whales.
A new global survey, released at a conservation meeting in Kenya, finds that more than 70% of species are at risk through snaring in fishing nets.
Other major threats include intentional catching, pollution, habitat destruction and military sonar.
The UN Environment Programme (Unep) is calling for an upgrade of international protection on eight species.
It wants the Ganges river dolphin, Atlantic spotted dolphin, Northern right-whale dolphin and five other species to be given Appendix II status under the Convention on Migratory Species (CMS).
Existing protection measures on a further seven species should also be extended, it says.
A CMS summit is taking place this week at Unep headquarters in Kenya.
"Small cetaceans are amongst the most well loved and charismatic creatures on the planet," said Unep executive director Klaus Toepfer in a statement.
"Sadly these qualities alone cannot protect them from a wide range of threats; so I fully endorse measures to strengthen their conservation through the CMS and other related agreements."
Appendix II status does not confer mandatory protection, but is designed to induce relevant countries to draw up conservation agreements.
Two such agreements for small cetaceans are already in place, one in the Baltic Sea, the other covering the Mediterranean and Black Seas.
The Unep report attempts to calculate the relative importance of the various factors which put dolphins and whales at risk.
It finds that 26.5% of the threat comes from accidental bycatch, 24.9% from deliberate hunting, and 21.2% from pollution.
Two years ago a scientific study found that about 800 cetaceans die each day through being snared in fishing nets.
Other factors identitied by the new report include habitat degradation, depletion of fish stocks on which the cetaceans feed, culling, and noise, for example from naval sonar.
Mark Simmonds, director of science at the Whale and Dolphin Conservation Society, believes that the Unep report may underestimate the true scale of the issue.
"What it's doing is indicating where there's very strong evidence of a direct threat to a particular species," he told the BBC News website from the Nairobi meeting, "and it's very difficult to get that kind of evidence.
"Many of these species we know very little about, particularly the deep diving ones.
"On the other hand, we know enough to say that pretty much all the river dolphins are threatened, and in fact the next mammal to go extinct will probably be a river dolphin - it's as serious as that."
Further measures are being debated at the CMS meeting, including a proposal to list the Mediterranean population of the short-beaked dolphin onto Convention Appendix I.
This would oblige countries around the Med to restore habitat and change trends which are contributing to the dolphin's demise - in this case, principally the reduction in stocks of sardines and pilchards which it eats.