Ka Wai Ola - Office of Hawaiian Affairs, Volume 26, Number 8, 1 August 2009 — Fish and contaminants [ARTICLE]

Fish and contaminants

In Liza Simon's otherwise excellent article on fish and mercury (July Ka Wai Ola ), the information regarding sahnon farming is incorrect. Everywhere that wild salmon and farmed sahnon share the waters, wild sahnon continue to decline. The problem is a fundamental ecological

Haw in sea-cage farming. Here's how it goes. When a wild fish falls ill, it has a harder tune making a living, and predators find it easier to catch. Thus diseased wild fish either starve or are eaten before they ean infect many other fish. Sea-cage fish, on the other hand, are fed by farmers and they are protected from predators by their cage. When they fall ill they live a long tune while shedding pathogen into the surrounding waters. The higher levels of pathogen cause higher levels of infection in wild fish, whieh then decline. Traditional Hawaiian fishponds did not have this problem because they included predators such as kākū, whieh controlled disease, and because fresh water welling up from the bottom of the pond allowed 'ama'ama to rid themselves of sea liee (whieh cannot tolerate low sahnity). Sea-cage farmers must treat their fish for sea liee by putting toxic chemicals such as emamectin ben-

zoate in the fish feed. Regarding contaminants, the 'ama'ama in Hawaiian fish ponds ate seaweed that grew naturally in the ponds, thus converting plant protein into animal protein. Sea-cage-raised carnivores such as kāhala, moi and sahnon are fed pellets eontaining ground-up fish, including large amounts of menhaden from the Gulf of Mexico, the ultimate destination of most agricultural chemicals in the continental United States. Neil Frazer Professor University of Hawai'i at Mānoa