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Dear Jim, Debbie and all
Starvation of nutrients reducing productivity is not necessarily the issue
globally. Certainly in tropical areas coral reefs are suffering from many
things but not from shortage of nitrogen. Mangrove swamps ( where they are
not being cut for shrimp farms or landfilled for housing) are expanding
because of the increased nutrients. Apart from all the obvious nutrient
sources, there is net positive gain of nutrients by the sea because in
tropical areas the nitrogen locked into the soil for centuries is being
washed into the sea as the forests are cut and the soil leaches into the rivers.
There is a growing body of evidence that the selective pressure of marine
fisheries has reduced size at maturity. I think Jim Bonsack first proposed
it but small rapidly reproducing fish have come to dominate trawl fished
areas. So it is quite possible that heavily fished salmon stocks have
taken the reproduce quickly before we get caught option.
steve
At 09:56 PM 3/9/00 -0000, you wrote:
>Attached is an article I wrote several years ago and is still relevant.
>On average size another thought. Two things control the catching of wild
>salmon. Time of year and net sizes. Net sizes are designed to let
>small fish escape therefore we selectively kill the large and presumably
>faster growing fish. Fish lay eggs in numbers in proportion to their size.
>Have we selectively culled large fish and therefore the fish we protect are
>actually laying few eggs and breeding a smaller fish which in turn will
>aggravate the situation?
>
>
>
>Jim Mackie
>
>
>
>
>
>Attachment Converted: E:\EMAILA~2\whereare.doc
>
Dr. Steve Oakley, Shell Prof. of Environmental Science,
Institute of Biodiversity & Environmental Conservation, Universiti Malaysia
Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia [log in to unmask]
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