|
===== A message from the 'toxicscaucus' discussion list =====
>From: Pete Myers
This abstract (below) summarizes a paper presented at the 1998 joint meeting of the American Fisheries Society Western Division, Alaska
Chapter and the North Pacific International Chapter, Anchorage.
October 1998.
It reports some remarkable findings which dramatically inject pollution issues into the salmon decline story. Very low level
contamination by polynuclear aromatic hydrocarbons (PAHs) experienced by salmon embryos causes a reduction by up to 60% of the return rate
of adults of the exposed cohort to their breeding site. According to the authors, the lower return rate is is indicative of reductions in
marine survival rates (see highlighted text). While this paper's focus is on the aftermath of the Exxon Valdez spill, PAH contamination
is widespread in US waterways as a breakdown product of weathered oil, including pollution from outboard motors.
They don't know what the mechanism for increasing marine mortality is, especially from embryonic contamination at such low levels. Two
hypotheses which occur to me (and no doubt there are many more):
- that the apparent mortality is a result of the contaminant screwing up the ability of the salmon to navigate back to the home stream.
- that the contaminant interferes with the osmoregulatory changes that allow
salmon to move from fresh to salt and back to fresh water. These changes are hormonally regulated.
----------------
Pink Salmon Demonstrate Acute and Long-Term Effects After Exposure to Very Low Concentrations of Polynuclear Aromatic Hydrocarbons
(PAH) During Incubation
R.A. Heintz, National Marine Fisheries Service, Auke Bay Laboratory, Juneau, AK
For four years after the Exxon Valdez oil spill, the Alaska Department of Fish and Game (ADFG) biologists recorded elevated
mortalities among pink salmon embryos incubating in the contaminated sections of affected streams. The persistence of these observations
was contrary to expectations because streambed contamination was thought to be minimal, and salmon eggs were not considered sensitive
to polynuclear aromatic hydrocarbons (PAH). In 1992, the National Marine Fisheries Service began examining the plausibility of the ADFG
observations by incubating pink salmon eggs in gravel contaminated with known quantities of oil. After following three brood years, we
conclude that pink salmon eggs are sensitive to low concentration of the PAH that characterize weathered oil and that effects can be
observed in eggs incubating downstream from the oil source. Embryos exposed to aqueous PAH concentrations of 1.0 ppb demonstrated a
two-fold increase in mortality compared with unexposed embryo, and a 10% reduction in growth during their first 6 months in saltwater. Fish
initially exposed as embryos to aqueous PAH concentrations of 15 ppb from the 1993 and 1995 broods experienced marine survivals 15% to 60%
lower, respectively than unexposed fish. Integrating the increased mortality for all the major life history stages estimates the relative
loss in reproductive potential to a cohort of exposed fish. These estimates are that expsed cohorts produced 38% and 42% fewer mature
adults than unexposed cohorts in the 1993 and 1995 broods, respectively. Reduced growth also could result in further reductions
reproductive potential through reduced fecundity. Our laboratory observations indicate the plausibility of the ADFG observations. This
conclusion is further supported by the fact that the minimum effective concentrations of PAH identified in our studies are bracketed by the
range of contamination levels reported in and around pink salmon streams in PWS for at least 4 years after the spill.
(PWS is Prince William Sound)
Delores Broten,
Reach for Unbleached! Foundation,
Box 39, Whaletown BC Canada V0P 1Z0
Ph/fax: (250) 935-6992
http://www.rfu.org/
dbroten@rfu.org
Translate
this page automatically. 
|
