By Alex Kirby
BBC News Online environment correspondent, in Sorrento
Whales are hardly ever in competition with humans for fish, a world respected fisheries expert says.
Japan has argued that cetaceans are damaging fish stocks
Dr Daniel Pauly, of the University of British Columbia, Canada, says Japan is wrong to blame whales and other marine mammals for reducing fish stocks.
Arguing that whales eat fish which could feed the world's hungry people is
"cynical and irresponsible", he said.
Dr Pauly's comments were made as the International Whaling Commission began its four-day annual meeting in Italy.
The IWC has been split for years between a slowly dwindling anti-whaling majority and a group led by Japan, Norway and Iceland, which wants the 1986 moratorium on commercial whaling lifted.
One of their arguments is the contention that whales (with the other cetacean groups, dolphins and porpoises) are eating fish that would otherwise feed humans.
But in a report for Humane Society International - called Competition Between Marine Mammals And Fisheries: Food For Thought - Dr Pauly and his co-author, Kristin Kaschner, say this is untrue.
They acknowledge that whales and pinnipeds (seals and sealions) eat several times as much as the 125-150 million tonnes caught annually by people - possibly as much as 5-600 million tonnes in total.
But they say: "What whales consume is largely stuff that we do not catch, in areas where we do not fish."
The authors reached their conclusion after mapping fish catches against what whales are known to eat.
Dr Pauly told BBC News Online they had made little use of Japanese data on whales' diet obtained from animals killed in Japan's scientific whaling programme.
As part of the Sea Around Us Project, which he directs at the university's Fisheries Centre, Dr Pauly and Kristin Kaschner have developed a unique grid of 180,000 "cells" covering the world's oceans, each of them a square measuring half a degree.
At the Equator they are about 30 nautical miles (55km) square.
They mapped catches in these cells during the 1990s and compared them with what the whales were known to have eaten.
The results showed that the degree of overlap between cetacean and human appetites was "very low".
Marine mammals, the authors say, find most of their food where fisheries do not fish, and most of what they eat (for example, plankton and deep sea squid) are of no interest to the fishing fleets.
They say 99% of the grids are "low overlap areas".
Dr Pauly told BBC News Online: "The bottom line is that humans and marine mammals can co-exist. There's no need to wage war on them in order to have fish to catch.
"And there's certainly no cause to blame them for the collapse of the fisheries. It's really cynical and irresponsible for Japan to claim that the developing countries would benefit from a cull of marine mammals."
"It's the rich countries that are sucking the fish out of the poor countries' own seas."