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Joel,
Even though you have done some kind of assessment of water quality that
this stock has been raised in, I am concerned that water quality is often
prematurely eliminated as a possible piece of the problem. Based on standard
WQ screening that is often done by state agencies to assess CWA compliance,
and, resultant 303d listings, 'best available science'- based claims are
usually very questionable. The federal CWA compliance process puts
tremendous pressure on the state WQ agencies to avoid finding any more
problems than funding could likely be found for fixing (unless litigation
pushes action). Insipid 303d listings often result, and databases that
fisheries agencies rely on for suitability of waters for aquatic health of
salmon are much less than what they should be. As a result, most fishery
managers are very mislead and good questions such as your bioenergetics
inquiry are stymied.
For example: chronic low-dose behavioral effects of lead in fish(and
subsequent population decline) can result from levels in watyer that are far
below the usual 303d listings criteria; some states seem to have a great
deal of difficulty applying the EPA 'hardness-dependent metal' corrections
to their field and lab results that determine 303d. Very small sampling
numbers also miss very many exposures.
Salkmonids can be affected by very minute quatities of lead, swimming
capacity can be affected. Lead, by affecting ALAD, decreases O2 carrying
capacity of the hemoglobin (among many other relevant effects). This issue
is very relevant to migrating salmon species. Lead levels are usually
anthropogenic, and many organisms have not evolved very good defenses for
the increased envinomental exposures. Good luck.
Ray Kinney
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