7. Role of Lipids in Fish Populations
151
7.2.4.3. Other Stressors
A wealth of literature is available on the effects of mixed contaminant effluents on
fish health, particularly fish populations exposed to pulp and paper mill discharges. Few of these studies, however, have reported on lipid dynamics in fish
following exposure to contaminants in these effluents. Notably, Hodson et al.
(1992) found that white sucker, Catostomus commersoni, residing downstream of
pulp mill discharges had increased lipid levels as reflected by total carcass lipid.
Similarly, Sandstrom et al. (1988) found elevated lipids in perch, Percafluviatilis,
from Baltic coastal areas but observed reduced gonad growth in the exposed fish.
Both these studies attributed altered energy metabolism in these fish to disturbances or changes in the way that energy was allocated within the organism. In
contrast to these findings, however, McMaster et al. (1991) observed reduced lipid
stores, smaller gonads, and decreased energetic commitment to growth in white
sucker exposed to paper mill effluents. Adams et a!. (\ 996) also found significantly reduced lipid stores compared with the reference as reflected by the
visceral-somatic index in redbreast sunfish, Lepomis auritus, below a pulp mill
discharge. In this case, however, growth was elevated in these fish as was the
condition factor. The somewhat contrasting results among these four studies
relative to energy allocation to growth, lipid storage, and reproduction probably
reflect site-specific differences in energy allocation strategies that may be related
not only to the nature and magnitude of contaminant exposure but also to the
influence of other environmental and ecological factors such as food and habitat
availability (Adams et a!., 1996).
The sublethal effects of textile mill effluents on lipid composition in different
tissues of fish are similar to those reported for paper mill discharges. A decline in
lipids occurred in both muscle and liver, which was attributed to utilization of this
energy source for the purpose of mitigating stress caused by the textile mill
effluents (Raj an, 1990). Tannic acid, which is a major constituent of tannery
effluents, caused a decrease in the total lipid content of liver and muscle when fish
were exposed to 59 ppm for only 96 h (Somanath, 1991). As other investigators
working with a variety of contaminant stressors have concluded, the decrease of
lipids in the liver and muscle could have been caused by fatty acid oxidation to
meet the additional energy requirements under stress conditions.
The indirect effects of contaminants on fish health and lipid dynamics can be
illustrated by the study of Munkittrick and Dixon (1988), in which lakes containing elevated levels of heavy metals impaired lipid dynamics and reproduction in a
population of white sucker. Fish from the contaminated lakes had decreased
muscle lipids, serum lipid concentrations, and visceral lipid reserves. Reproduction was impaired as evidenced by decreased egg size and fecundity, suggesting
that less energy was committed to gonad development in fish from the contaminated system than in fish at nonaffected sites. Most of the alterations in lipid
dynamics and reproduction in these fish were attributed to nutritional deficiencies
as a result of the chronic effects of elevated metals in the sediment on the food
151
7.2.4.3. Other Stressors
A wealth of literature is available on the effects of mixed contaminant effluents on
fish health, particularly fish populations exposed to pulp and paper mill discharges. Few of these studies, however, have reported on lipid dynamics in fish
following exposure to contaminants in these effluents. Notably, Hodson et al.
(1992) found that white sucker, Catostomus commersoni, residing downstream of
pulp mill discharges had increased lipid levels as reflected by total carcass lipid.
Similarly, Sandstrom et al. (1988) found elevated lipids in perch, Percafluviatilis,
from Baltic coastal areas but observed reduced gonad growth in the exposed fish.
Both these studies attributed altered energy metabolism in these fish to disturbances or changes in the way that energy was allocated within the organism. In
contrast to these findings, however, McMaster et al. (1991) observed reduced lipid
stores, smaller gonads, and decreased energetic commitment to growth in white
sucker exposed to paper mill effluents. Adams et a!. (\ 996) also found significantly reduced lipid stores compared with the reference as reflected by the
visceral-somatic index in redbreast sunfish, Lepomis auritus, below a pulp mill
discharge. In this case, however, growth was elevated in these fish as was the
condition factor. The somewhat contrasting results among these four studies
relative to energy allocation to growth, lipid storage, and reproduction probably
reflect site-specific differences in energy allocation strategies that may be related
not only to the nature and magnitude of contaminant exposure but also to the
influence of other environmental and ecological factors such as food and habitat
availability (Adams et a!., 1996).
The sublethal effects of textile mill effluents on lipid composition in different
tissues of fish are similar to those reported for paper mill discharges. A decline in
lipids occurred in both muscle and liver, which was attributed to utilization of this
energy source for the purpose of mitigating stress caused by the textile mill
effluents (Raj an, 1990). Tannic acid, which is a major constituent of tannery
effluents, caused a decrease in the total lipid content of liver and muscle when fish
were exposed to 59 ppm for only 96 h (Somanath, 1991). As other investigators
working with a variety of contaminant stressors have concluded, the decrease of
lipids in the liver and muscle could have been caused by fatty acid oxidation to
meet the additional energy requirements under stress conditions.
The indirect effects of contaminants on fish health and lipid dynamics can be
illustrated by the study of Munkittrick and Dixon (1988), in which lakes containing elevated levels of heavy metals impaired lipid dynamics and reproduction in a
population of white sucker. Fish from the contaminated lakes had decreased
muscle lipids, serum lipid concentrations, and visceral lipid reserves. Reproduction was impaired as evidenced by decreased egg size and fecundity, suggesting
that less energy was committed to gonad development in fish from the contaminated system than in fish at nonaffected sites. Most of the alterations in lipid
dynamics and reproduction in these fish were attributed to nutritional deficiencies
as a result of the chronic effects of elevated metals in the sediment on the food