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oil-polluted Abers and from nearby reference stations. These may
be useful indices of pollutant stress. They include blood cholesterol/
HDL cholesterol, liver ascorbic acid, and skeletal muscle-free amino
acid ratios in fish; and adductor muscle-free amino acid ratios in
oysters. Blood glucose also has potential as an index of stress in fish,
if the fish can be captured and blood samples taken very quickly.
Alternatively, useful information can be obtained if degree and duration
of capture- induced stress can be standardized for reference and experimental
fish. In such a case, the index of chronic pollutant stress is
hypoglycemia, reflecting a loss or diminuation of the capacity of the
hypophyseal-interrenal system to respond to stress.
Several of the alterations in biochemical parameters in oil-polluted
fish and oysters are indicative or symptomatic of poor nutritional status
(e.g., depressed muscle glycine, depletion of liver glycogen and ascorbate,
etc.). This may be related to histopathological lesions, reported
by Haensly and Neff in this publication in the gut and liver of plaice
from the oil-contamianted Abers.
One difficulty in using biochemical and histopathological parameters
as indices of pollutant stress is that one is not always certain that
animals from the impacted and reference sites are from the same population
and therefore can be compared biochemically and histopathologically.
The only way to establish convincingly that differences observed in indicator
parameters in reference and impacted populations are due solely or
primarily to the pollution incident under investigation, is to have
comparative data collected before the pollution incident. This usually
is not available. The oysters used in this investigation are a recently
introduced species Crassostrea gigas and are from a common breeding
stock throughout Brittany. Genetic differences between reference oysters
and oysters from the Abers are therefore extremely unlikely. However,
the extent to which plaice from the west and south coast of Brittany
(reference sites) mix and interbreed with plaice from the northwest
coast (site of the Abers) is not known. Some intermixing undoubtedly
occurs. It seems likely, therefore, that many of the differences we
have reported between oysters and plaice from the Abers and those from
reference stations are attributable directly or indirectly to impacts
of the Amooo Cadiz oil spill.
There has been substantial improvement in condition of oysters
and plaice in the Abers during the timecourse of this investigation
(up to 27 months after the spill). Recovery is still not complete,
however .
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