to go anoxic or nearly anoxic at depth, and under such conditions 
carbonic acid is produced which will dissolve the outer layer of 
the oyster shell; thus, producing the "scrubbed clean" look of 
the oysters. He has seen this occur in estuarine waters and in 
the laboratory despite the heavy buffering of the salts present. 
If in addition to producing carbonic acid, anoxic conditions hold 
for a long period when the oysters were otherwise stressed, then 
mortality would occur. This hypothesis is consistent with the 
data and cannot be disproved as our sampling periods were far 
enough apart that we might not have detected the event causing 
the anoxia. 
Golden Shiner Experiments 
Table 7 indicates that different stations show different cor¬ 
relations between nonsurvivorship and four factors noted during 
autopsies. Both Campbell stations and Tenneco Downstream had 
significantly higher infection percentages of fungus. The fungus 
appeared to be Saprolegnia sp. but was not identified. 
Saprolengia is not an obligate parasite. Usually it occurs as a 
saprophyte. Its abundance at these stations indicates high con¬ 
centrations of organic material. 
The white nodules are problematic. Their identification is 
unknown. They are white, translucent, hard, brittle and sub- 
spherical to ovoidal to rounded irregular in shape. Largest 
diameter is less than 1.5 mm. They occur in patches usually on 
the ventral half of the body or on the fins. They are firmly 
attached to the scales, fin rays or opercle but can be broken 
loose by scraping. None were noted in specimens which had sur¬ 
vived nor in any specimen from Campbell Upstream or the control 
station. It was thought that these might be the results of an 
interaction between the calcium of the boney scales and fin rays 
and some ingredient in Davidson's fixative. Arguments against 
this are numerous. The crayfish have as much or more calcium in 
their exoskeletons than the fish scales, but no crayfish was ever 
found with one. The placement on the body in discrete patches 
argues against any random process, and the fact that there were 
significantly more or less of these at certain stations adds 
doubt to any simple explanation. 
Foreign matter on the gills irritate the gills, cause stress 
symptoms and synergistically increase toxicity of other sub¬ 
stances.* It is therefore conceivable that the foreign material 
noted on the gills of fishes that died at the control station 
was a contributing factor to their death. In addition to silt 
particles on the gills, fibers resembling those from toilet paper 
were noted on one fish's gills. This indicates that untreated 
domestic sewage may find its way into the stream above our con¬ 
trol station. 
* Wilber, Charles G. 1976. The biological aspects of water pollu¬ 
tion. Charles C. Thomas, Publisher, Springfield, IL, 296 p. 
37 
