Letter: Yellowtail’s ‘avoid’ rating justified


SeafoodSource staff

Published on
September 16, 2009

Editor’s note: The following is a letter to the editor submitted by Geoff Shester, Seafood Watch senior science manager for the Monterey Bay Aquarium, in response to the SeafoodSource story “A mixed score for Japanese yellowtail”:

The 15 September Seafood Source article by Chris Loew, entitled “A Mixed Score for Japanese Yellowtail,” noted the environmental issues highlighted by Monterey Bay Aquarium’s Seafood Watch for Japanese yellowtail (hamachi), which led to the “avoid” rank. Those issues are “high reliance on wild-caught fish to create feed and serious concerns over disease and water pollution.”

Commendably, SeafoodSource reported a great deal of information regarding Japan’s management of the wild yellowtail fishery, as well as concrete examples of feeds and feeding strategies for yellowtail culture. In fact, the impacts the article described from visiting one farm largely corroborate the research we presented in our extensive evaluation of Japanese yellowtail farming, which can be found on our Web site. The full report is also available.

Seafood Watch would like to add to this discussion and point out real concerns regarding the environmental sustainability of farming yellowtail in Japan. First, a large amount of wild fish is used to feed a small amount of farmed yellowtail. Consider the example in the article of “Expander Pellet” with 40 percent fishmeal and FCR of 1.2, which would fall on the low end of the range we reported in our assessment. When translated to wild fish in vs. farmed fish out, the SeafoodSource example would mean that over 3 kilograms of wild fish are used to feed 1 kilogram of farmed yellowtail. The ratio is even higher during the last year of grow out when yellowtail are fed raw fish, at ratios up to 20 pounds of wild fish for every 1 pounds of weight gain in farmed yellowtail.

In addition, disease and parasites can cause serious loss of farmed fish and spread to wild fish. Particularly troublesome to yellowtail are skin and gill flukes. The Australian researcher, Hutson, evaluated disease risk to yellowtail farms and stated that the skin fluke poses a high risk, which could result in sustained high rates of mortality and significant loss to the industry. Also, the experiments by Chambers and Ernst in Australia showed that flukes spread from farms and infected “sentinel” yellowtail placed downstream from the farms. Finally, pollution from yellowtail farms in Japan is generally more severe than your example of Hiburi Island, which is well flushed by tidal flows. Yellowtail farms in Japan are frequently farmed in enclosed coastal bays, which are not well flushed. Unfortunately, Japan’s coastal waters are experiencing recurring red tides that damage fisheries.

Again, we are glad to see such a high profile publication highlighting the conservation concerns with farmed yellowtail, and that your site visit served to confirm several of the issues we had identified, which give Japanese farmed yellowtail an “avoid” ranking. In the future, it might be useful to point out some of the innovations currently occurring in this industry that help alleviate these concerns, including some which we have highlighted in our report, so that your readers can better understand the intention of the Monterey Bay Aquarium to promote market incentives for more sustainable aquaculture.

Geoff Shester, Ph.D.
Seafood Watch senior science manager
Monterey Bay Aquarium

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