Re: NANFA-- Atlantic Salmon Farming

Jay DeLong (
Mon, 10 Nov 2003 09:42:03 -0800

At 04:43 PM 11/9/2003 -0600, you wrote:
>Thanks to everyone who suggested information sources.
>And to finally answer your question, Jay - yes, the focus of my
>presenation will be Atlantic salmon farmed in the Atlantic. As to my
>statement regarding salmon farming's "impacts on the ocean environment,"
>the basic research I've done so far makes mention of tropical fish
>harvests being used to feed the salmon, antibiotics being released into
>the water, and large concentrations of fish waste collecting at the site
>of the pens.

Thanks, I now see you mean ocean vs freshwater. Atlantic salmon grow
quickly and have a high feed conversion rate = a measurement of food
efficiency = how food fed becomes new fish biomass. This is why Atlantics
are desireable for culture and why they're so cheap in stores. (Atlantic
salmon costs about half of what Pacific salmon costs in groceries in my
area.) If you are interested I can find comparative conversion rates.

Antibiotics are given fish through their feed, so uneaten feed finds its
way to the bottom along with fish waste. Waste is a problem; I've heard
freshwater growout net pens referred to as "hanging gardens" and the bottom
below the pens is covered by waste and the products of bacterial
decomposition-- it's like a dead zone of white and gray powder and
goo. This could be improved by placing pens in areas of greater flow
(tidal exchange). Flow is important for the health of the fish, too,
because the pens can hold fish more densely and more fish equals more
money. But it's not that simple unfortunately. And calmer conditions make
protecting and managing the pens easier.

Another potential environmental impact may result from these these pen
facilities attracting fish predators like seals and sea lions. These
mammals can become local nuisances and may have undesireable impacts on
other species or runs of fish. Anadromous runs are like sitting ducks.

Good luck. It sounds like a great project.

Jay DeLong
Olympia, WA
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