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Subject: Salmon weights
From: Debbie MacKenzie <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Thu, 9 Mar 2000 06:16:02 -0400

text/plain (46 lines)


John Gilbey wrote:

>I agree marine survival is a major problem, but just one of many. I repeat,
>the fishing effort has dropped in recent years but the returns stayed down.
>Further, have you any evidence for lower body weights in returning salmon? I
>would be very interested in some references. I have seen no data to support
>this view.

DFO's work includes a huge amount of research into Atlantic and Pacific
salmon, yet weight-at-age and size-at-age data I have yet to find. I have
been "told about" a 20 year study that was done on a couple of Alaskan
salmon stocks that showed a declining trend in weight-at-age, but have not
actually seen it. Apparently it was done at the Auke Bay Lab - I've had a
fairly lengthy discussion on this topic with a fisheries manager from
Alaska which is posted on my website:  ...but, no, I have not seen that

>I thought that El Nino was a reversal of ocean currents which
>resulted in the nutrient rich lower water layers no longer upwelling near
>the South American coast, thus no nutrients for the algae?!

Yes, upwelling or lack thereof, is part of the picture of El Nino on which
I am no expert. The lack of "upwelling" due to El Nino is given as the
reason that surface water in the Bering Sea has been so nutrient poor
during the last couple of summers that there have been major blooms of
coccolithophores. If it is not upwelling, then are the nutrients
concentrated near the bottom? If the nutrients are concentrated near the
bottom why are bottom-feeding gray whales, who feed all summer in that
area, dying of starvation?

Just trying to make sense of the whole picture.

Debbie MacKenzie

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