For all practical purposes, the statement was correct.
From The Institute of Cetacean Research, 2000 http://luna.pos.to/whale/sci_cri.html
" In the waters around Japan where catches in certain fisheries are declining, Japan's research catch of whales reveals that minke whales are eating at least 10 of the target species of these fisheries including Japanese anchovy, Pacific saury, walleye Pollock and others (Government of Japan, 2000)."
"Off the Pacific coast of Japan, Bryde's whales feed on krill, Japanese anchovy and chub mackerel (Scomber japonicus). In the waters around Bonin Islands, they fed on krill and lantern fish. In the East China Sea, they fed mainly on Japanese pilchard (Sardinops melanostictus), Japanese anchovy and horse mackerel (Trachurus japonicus) (Government of Japan, 2000)."
"Sperm whales feed not only on squids but their diet also includes commercially important fishes such as rockfishes, cods, Pacific saury, and Japanese pilchard."
"Data from Iceland indicates that of sixty-eight minke whale stomachs examined, 51% contained fish only, 22.1% krill only and 25.0% fish and krill together (Sigurjonsson et al., 2000)."
Minke, Bryde's, and Sperm are the three species "that the Japanese consider huntable".