STRESS AND FISH DECEASES IN THE PASVIK RIVER

Contamination of heavy metals and river euthrophication may create stress conditions for vital functions of fish. Whitefish from the localities most distant to Nikel, exhibited some pathological changes in gills and gonad asymmetry, but only negligible changes in liver and kidney. One should also notice a high percentage of fish parasitic invasions in these regions. The given data may indicate fish stress and less resistance to parasitic invasions. The fish pathology was, however, most severe in localities close to Nikel.

Frequency of whitefish pathologies from various areas

Pathological abnormalities were manifested in changes of colour and structure of liver, kidney and gills. In Kuetsijarvi, practically all caught fish had disorders in vitally important organs. Here we observed the maximum pathological degeneration of tissues and organs of fish.

Frequency of detected fish pathology (in % of total numbers of examined fish) and its seasonal variability in different regions of the Pasvik River System

Pathology
Kuetsijarvi
Svanvik
Pasvik III
Vaggatem
Sept
Jun
Sept
Jun
Sept
Jun
Sept
Change of colour
4.3
82.4
0.0
83.0
0.0
36.9
0.0
"Transparency cranium"
3.7
80.2
0.0
87.2
0.0
30.6
0.0
Change of gills
17.1
46.2
13.6
100
3.2
45.5
0.0
Change of liver
90.7
96.6
83.8
82.4
83.9
92.0
27.4
Change of kidney
32.1
64.7
62.2
84.4
19.4
50.0
9.6
Nephrocalcitosis
3.7
15.3
2.7
0.0
0.0
0.0
0.0
Change ofmale
67.4
8.7
57.2
6.3
32.0
26.1
6.8
gonadsfemale
18.6
30.6
-
-
-
-
-

Typical pathology for whitefish was abnormalities in kidney, liver and gills.

Kidneys connective tissue and nephrocalcitosis of whitefish
Some changes in gill rakers as result of pollution influence (A), compared to normal gills (B).

82,4% of fish from Kuetsijarvi had skin depigmentation.

"Transparency cranium"
"Skin depigmentatio"

Whereas in the upper part of the river this pathology was absent. Liver adipose depletion were observed in 96,6% of the fish from Kuetsijarvi. Kidney anomaly was also frequently observed;64,7% had expanded kidneys due to connective tissue and 15,3% fish had nephrocalcitosis. In fish from the upper part of river, only 9,6% showed formation of connective tissue in the kidneys and none had nefrocalcitosis.The highest occurrence of pathological abnormalities were observed during spring. In conclusion, one should take into account that anthropogenic load in the Pasvik river is a result of airborne pollution, waste from smelters, domestic sewage and river regulation. Their simultaneous influence may appear to create severe stress conditions for fish.


Each species had specific pathology.

Pike had blue and green color of the muscles, liver and body.


For male of perch was typical specific twisted gonads. Gonads had the form of brain. Frequently male had connection between forward part of gonads or one of gonads was reduced.
Female of perch had only one developed gonad.The form and colour of a liver were strongly changed.

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