"Considering the media attention given to stopping the hunting of whales (large cetaceans) for human consumption, it may come as a surprise that people are eating more marine mammals than ever before," the editorial said.
Dr Costello and co-author Scott Baker, a former University of Auckland researcher, were commenting on an American study which showed that the consumption of small cetaceans and other marine mammals had increased in some regions over the past two decades.
Hunting of large whales was closely monitored and widely condemned, but fishing of smaller species such as pilot whales, river dolphins and manatees was under-researched.
The American study found 125 nations had eaten a total of 92 species.
The increase in targeted fishing of marine mammals included some disturbing practices.
Dr Costello cited a field report from Lombok, Indonesia, which showed fishermen catching spinner dolphins to eat but also to use as live bait for sharks. This practice was influenced by the popularity of the Asian delicacy shark-fin soup.
The increase in whale meat consumption was in part blamed on poor countries which had exhausted traditional sources of protein and were now looking to "the last great hunting ground" - the ocean. This trend was now being researched in depth.
But many developed countries - United States, Canada, South Korea - also featured high on the list of nations that consumed a range of marine mammals.
The editorial outlined the "daunting" ethical, cultural and ecological hurdles to conserving marine mammals. Greater protection for marine mammals would require not only wide-ranging international agreements, but reflection on some of the double-standards with regards to catching and killing fish for commercial and recreational reasons.
Dr Costello: "One of the objections to killing whales is that you can't kill whales humanely. But ... there's big fish which have the same physiology and stress responses and hormone systems and people hunt them for hours sometimes."
Eating more
Number of marine mammals species eaten, by country, 1990-2009:
32 Japan
19 Greenland, Indonesia
18 Ghana, South Korea
17 United States, Taiwan, Philippines
16 Peru, Russia
15 Canada, Sri Lanka
14 St Vincent and Grenadines, Brazil
On the menu
Polar bears, spinner dolphin, narwhal, pygmy beaked whale, South Asian river dolphin, Chilean dolphin, long-finned pilot whale