Page 840 - The Toxicology of Fishes

820 The Toxicology of Fishes

Role of Other Stressors in Limitations of Great Lakes Lake Trout Recruitment................................ 847
Chemical Contaminants Other Than HAHs................................................................................847
Loss of Breeding Habitat.............................................................................................................849
Predation.......................................................................................................................................849
Thiamine Deficiency ....................................................................................................................849
Case Study: Assessment of the Effects of AhR Agonists on
Reproduction and Survival of Lake Trout in Lake Ontario.............................................................850
Lake Trout Exposure History Assessment for PCBs, PCDDs, and PCDFs in Lake Ontario ........851
2,3,7,8-Tetrachlorodibenzo-p-Dioxin (2,3,7,8-TCDD) Toxicity
Equivalence Risk Modeling in Lake Trout from Lake Ontario.............................................852
Summary ................................................................................................................................................854
Ecoepidemiological Criteria.........................................................................................................855
Probability...........................................................................................................................856
Time-Order..........................................................................................................................856
Strength of Association ......................................................................................................857
Specificity ...........................................................................................................................858
Consistency of Association.................................................................................................858
Predictive Performance.......................................................................................................859
Coherence ...........................................................................................................................860
Conclusion..............................................................................................................................................861
Acknowledgments..................................................................................................................................861

Introduction
The Great Lakes are the most important aquatic natural resource in North America. The Great Lakes
basin is home to approximately 40 million people in the United States and an additional 20 million in
Canada (Figure 21.1). The Great Lakes have been important in commerce (shipping and industry),
agriculture, tourism, and recreation. The multitude of uses of these natural resources has led to a complex
set of management goals that have not always been harmonized. The Great Lakes have historically
supported fisheries, but direct human management and inadvertent alterations of the Great Lakes eco-
system have occurred and dramatically influenced the fisheries of the Great Lakes (Evans, 1988). Factors
that have influenced Great Lakes fish populations include commercial fishing; both intentional and
unintentional introduction of non-native, exotic, or alien species; stocking of different genetic strains of
native fishes; and habitat loss or degradation, including decreased water quality (Eschmeyer, 1968;
Eshenroder and Amatangelo, 2002; Koonce, 1990; Smith, 1971). Notable among these have been
overfishing of certain populations, introductions of forage fishes and Pacific salmon, parasitism by the
sea lamprey, changes in invertebrate species, and subsequent changes in nutritional status of predators
(Brown et al., 2005; Eck and Wells, 1986; Miller and Holey, 1992; Muth and Busch, 1989), all of which
have had adverse affects, particularly on lake trout (Salvelinus namaycush) populations of the Great
Lakes.
Lake trout in Lake Michigan have not been naturally reproducing for over five decades. The lake trout
populations in both Lakes Michigan and Ontario are maintained by stocking programs because natural
reproduction of the populations is not sufficient to sustain the harvestable populations (Holey et al.,
1995; Mac and Seelye, 1981b; Willford et al., 1981). There has been evidence of natural reproduction
in Lake Huron (Weber and Clark, 1984), and populations have continued to reproduce naturally in Lake
Superior, where reproductive success is improving (Curtis, 1990). Some studies have indicated that these
recoveries are correlated with reductions in chemical contaminants observed in lake trout eggs (Cook
et al., 2003; Mac and Schwartz, 1992; Mac and Seelye, 1981a,b).
Chemical contamination has resulted in degradation of key habitats, reduced habitat quality, and
subsequent losses to certain fish and wildlife populations. For nearly two centuries, the Great Lakes
have been the receiving waters for industrial and municipal wastes, as well as agricultural runoff. The
fact that the lakes were so large resulted in the commonly held thought that it was impossible to
contaminate the lakes to a sufficient degree to cause adverse environmental effects. As the populations