Page 965 - The Toxicology of Fishes

Case Study: Pulp and Paper Mill Impacts 945

paper mills. Studies conducted after changes in mill bleaching technology showed that exposure to PME
compounds, based on induction of MFO activity, exists but at much lower levels than before modern-
ization. Alterations in sex steroid hormones, growth, gonad size, and fecundity continue to be documented
although species responses differ and difficulties remain in establishing direct cause and effect linkages
with the PME (Karels et al., 1998; 2001).
Field studies conducted in Canada (Jackfish Bay, Lake Superior, Ontario) from 1988 to present day
have documented improvements in fish responses to PME although reproductive impairment in white
sucker (Catostomus commersoni) and lake whitefish (Coregonus clupeaformis) remains (McMaster et
al., 1991; Munkittrick et al., 1991, 1992a,b, 1994, 2000a). Alterations in endocrine and reproductive
function include smaller gonad and egg size, increased age at sexual maturation, decreased levels of
reproductive steroid hormones, and altered expression of secondary sex characteristics (McMaster et al.,
1991; Van Der Kraak et al., 1992, 1998). Jackfish Bay continues to be the subject of intense study examining
reproductive performance in fish (McMaster et al., 1992, 1995, 1996a; Munkittrick et al., 2003).
In addition to the Swedish, Finnish, and Canadian field case studies, additional studies have examined
the potential of PMEs to affect fish. Some field and laboratory studies have shown that PMEs discharged
from modernized mills affect fish reproduction (Adams et al., 1992; Dubé and MacLatchy, 2000a, 2001;
Gagnon et al., 1994a,b; Karels et al., 1998; Kovacs et al., 1995; Leblanc et al., 1997; McMaster et al.,
1996b; Soimasuo et al., 1998b). Other studies, however, have failed to observe reproductive effects in
fish (Borton et al., 2000a, 2003; Kovacs et al., 1996; Swanson et al., 1994, 1996). Most recently, a
national evaluation described the existing response patterns for fish exposed to PMEs across Canada
(Environment Canada, 2003; Lowell et al., 2004). The predominant pattern was decreased gonad weight
and increased liver weight, condition factor, and weight at age. These responses are believed to be
indicative of some form of metabolic disruption or impairment of endocrine functioning in combination
with an eutrophication effect (Environment Canada, 2003; Lowell et al., 2004). Thus, as of today, it can
be concluded that reproductive effects occur in fish exposed to some PMEs, but effects are not always
consistent across mills, studies, seasons, or species, and the basis for the inconsistencies is unknown.

Approaches Used to Assess PME Effects on Fish

The assessment of PME impacts on fish has a long history and has resulted in an understanding of
effluent effects at different levels of biological organization. Of equivalent significance is how PME
studies have advanced our understanding of experimental and statistical design and have developed novel
field, mesocosm, and laboratory techniques and decision-making approaches (Dubé, 2004). These
advances have benefited the industry as a whole as well as influenced effects assessment for other sectors
such as metal mining and oil and gas (Ayles et al., 2004; Environment Canada, 2001). PME effects
assessment is no longer at an exclusive stage of measuring effects but has progressed to a stage of
determining which effects are ecologically important and require mitigation (Dubé, 2004; Munkittrick
et al., 2000a).

Study Design Considerations for Fish
Any study design for assessing contaminant effects such as PME on fish should include the following
(Environment Canada, 1998, 2001):
• Definition of the goals and objectives of the study
• Site characterization or description of background information for the study
• Detailed timetable for conducting the study
• Description and justification for the species, population or community selected for study
• Selection and justification for the indicators that will be measured to assess if a change has
occurred
• Description of the study design and how effects will be determined (e.g., where to sample,
what to measure, how frequently to sample)