They’re Tracking
pp. 75-76 · Read in the full issue
Poisonous Fish
From a Cook Islands Correspondent In recent years teams of research workers have been collecting data on the poisonous fishes of the tropical Pacific. The problem of toxic fish is a complex one about which little is known at present.
TNFORMATION is being collected *■- on the identity of toxic fishes, and their distribution. A method for rapid detection of toxic fish is also being sought for possible use on fishing grounds.
Dr. Bruce W. Halstead, of Cali fornia’s School of Tropical and Pre ventive Medicine, has been carrying out field studies for several years in widely scattered areas of the Pacific, including the Phoenix, Marshall, Caroline and Mariana Groups.
His organisation found that toxic species exist from the Galapagos Is lands to the Philippines and Okinawa, and from Midway to the Society Is lands. At Canton Island they found about 27 per cent, of the reef fishes were poisonous, and at Johnston Is land 75 per cent, of the species tested were toxic.
It's What They Eat Dr. Halstead’s theory is that fish poisoning originates in the diet of the fish, and there seems to be evi dence to support this. Other related factors are the age of the fish, its geographical locality, and the season.
Fish that are safe eating at one island may be highly toxic at another only 100 miles away. Fish and shell fish of the same species, but found in different areas of the same island, can be edible in one case and toxic in the other. These facts are con firmed by the findings of other scientific workers and by local know ledge.
For the last three years, Professor A. H. Banner, Director of Hawaii’s Marine Laboratory, and his team, have been investigating a common type of fish poisoning, ciguatera, found in the tropical Pacific. In an article in the South Pacific Bulletin last October Professor Banner states that the large red snapper caught at Palmyra Atoll are highly poisonous, yet at Washington Island, about 120 miles away, the same fish forms a large part of the local diet.
Residents of other Pacific islands (Over)
will know of similar phenomena. In the Cook Group, Rarotongan crayfish is safe to eat, but crayfish caught at Atiu, Mitiaro and Mauke, islands from 116 to 150 miles northeast of Rarotonga, are poisonous.
A type of mussel found at Raro tonga is safe in some localities but is toxic at others only a few miles away. Parrot fish, good eating at Penrhyn and Rarotonga, 700 miles apart, are toxic in certain areas of Atiu, Mitiaro and Mauke.
Some years ago, when Cook Islands labourers were employed at the French-owned phosphate island of Makatea, in the Society Islands, they discovered that they had to test their local fish before eating if they were to avoid poisoning.
Scientists agree there are at least four distinct types of fish poisoning in the Pacific and probably several more.
Professor Banner makes some in teresting observations on popular Is lands’ beliefs, some of which have been de-bunked by scientific tests.
“We could find no changes,” he writes, “in external appearance nor internal structure correlated with toxicity; no method of preparation re duced the toxicity, whether it was immediate cleaning and skinning— some fish were filleted while they were still flopping—or any technique of washing or cooking, « We found the toxin wa§ nQt altered by any normal heat, as in cooking, nor by cold, as in a re frigerator near 0 degrees Fahr. for 18 months e ',, , . , . also checked the belief that J! 1 ® 8 and a !j s . are [ e P9 ded by toxic fish ’ and that a toxic fish, when cooked with a silver com, will dis col.°f tl ?, e com. These beliefs were not true * Professor Banner and his team plan to study native remedies developed over thousands of years of treating cases of fish poisoning. He takes the view that native herb medicines should never be belittled without care ful investigation.