7.1.8 Persistant Toxic Contaminants in Water, Sediment, and Biota

7.1.8.1 Status

Spottail shiners were collected at 44 sites throughout the Great Lakes in September 1993 or 1994. Five to seven 10-fish composites were measured for total length (mm), wrapped in hexane rinsed aluminum foil, and frozen at -20°C until analysed for PCBs and organochlorines at the MOEE Laboratory (Ontario Ministry of Environment and Energy 1994a).

Calculated FFCI values, concentrations of total PCBs, and DDT are shown in Figure 20. An index value of 1 is designated as the Wildlife Risk Level. Higher values represent greater risk for piscivorous wildlife. Higher index values were generally more frequent in the lower Great Lakes, with the maximum observed values noted at the Grass R and Reynolds Aluminum sites in the St. Lawrence River and at the Welland Canal.

Figure 20. Forage Fish Contaminant Index (FFCI) for young-of-the-year spottail shiners in the Great Lakes in 1993 or 1994, with relative contributions from PCBs and DDT. Wildlife Risk Level=1.

PCB contributions to the index were generally high at most of the sampled sites. PCB residues were present in spottail shiners at 31 of the 44 sites sampled in 1993 or 1994 (70 percent), exceeding the IJC Aquatic Life Guideline of 100 ng/g at 13 sites (30 percent) (Figure 22). PCBs generally accounted for the largest component of the FFCI at most locations, with the exception of octachlorostyrene in the St. Clair River at Lambton Generating Station (15 ± 2 ng/g) and in Lake St. Clair (less than 5 ng/g), where a localized source contributed to the index. PCBs at Lambton Generating Station were below detection limits in 1994, a significant decrease from 1992 and 1993 (when the levels ranged from 131 ng/g to 168 ng/g). Unusually high localized PCB residues in forage fish on the U.S. side of the St. Lawrence River-in the Grass River and at Reynolds Aluminum-remain above 2500 ng/g. PCB residues in the Welland River just west of the Chippawa Power Canal (220 ± 39 ng/g) reflect upstream impacts. PCBs remain elevated on the U.S. side of the Niagara River downstream of the 102nd Street waste site (158 ± 20 ng/g). It is not known whether the continued declines at the Search and Rescue Station (244 ± 53 ng/g) are related to remedial measures (sediment removal) at Gill Creek in 1992. While PCB bioavailability at several sites in the Humber River watershed continue to fluctuate above the IJC guideline, concentrations remain elevated at the mouth of the river (174 ± 17 ng/g).

Total DDT concentrations in young-of-the-year spottail shiners were well below established guidelines (200 ng/g) at all sites.

BHC (Hexachlorocyclohexane) was elevated to 1985 levels at Cayuga Creek in 1994 (33 ± 11 ng/g). Four other occurrences in the Niagara River and Lake Ontario were less than 6 ng/g.

Chlordane was present at four sites-one at Fort Erie and three in Lake Ontario. Concentrations in spottail shiners did not exceed 12 ng/g.

HCB (hexachlorobenzene) residues have declined since the middle 1980s at Lambton Generating Station (the 1985 levels were 60 ± 13 ng/g; those in 1994 were 3 ± 1 ng/g). HCB did not exceed 1 ng/g in Lake St. Clair or the Detroit River in 1993 or 1994.

OCS (octachlorostyrene) was generally confined to the St. Clair River, Lake St. Clair, and the Detroit River. Levels have declined since the middle 1980s at Lambton Generating Station (having once been as high as 104 ng/g), but still persist in 1994 (15 ± 2 ng/g). OCS residues in juvenile fish declined downstream (less than 5 ng/g) to the mouth of the Detroit River (where none were detected).

Dow Chemical of Sarnia has been identified as the major source of HCB and OCS (DOE/MOE 1986).

Elevated concentrations of trichlorobenzene (89 ± 49 ng/g), tetrachlorobenzene (681 ± 338 ng/g), pentachlorobenzene (232 ± 95 ng/g), hexachlorobenzene (34 ± 6 ng/g), and BHC (51 ± 28 ng/g) were found in sand shiners just downstream of 102nd Street in the Niagara River. Although sand shiners may not be directly comparable to spottail shiners (for which comparable data are unavailable), these results indicate that leachate from several chemical disposal sites in the area, and contaminated river sediments near 102nd Street, may still be influencing contaminant levels in juvenile fish downstream.

Mirex was present only at the mouth of the Welland Canal (5 ± 3 ng/g).

Raw, log-transformed, and lipid-normalized contaminant values were used for temporal trend analysis. Since results were similar, only raw wet-weight-based values are shown graphically.

Temporal trends of PCBs are illustrated in Figure 21. Values are means with ± 95 percent confidence limits. Lines indicate significant correlations with time (p < 0.05). Total PCB concentrations in spottail shiners were negatively correlated with time at 12 of the 16 long-term sampling sites. Trend data indicate that PCB availability in the nearshore waters of the Great Lakes continues to decrease at most sites where contaminant inputs are low. Further containment of watershed inputs and point-sources of PCBs are required to reduce contaminant levels to acceptable levels at all sites.

Figure 21. Temporal Trends of total PCB concentrations of young-og-the-year spottail shiners in the Great Lakes from 1975 to 1994. Values are means +/- 95% confidence limits. Lines indicate significant correlations with time. (o = not detected).

7.2 Fish and Wildlife

7.2.1 Zooplankton

Zooplankton are the secondary producers of the aquatic food chain. They filter and eat the algae; their growth provides energy and nutrients in a form usable by fish. Populations of zooplankton cycle up and down seasonally in response to temperature and food availability as well as to predation by fish. The degree of predation can be related to fish stocking: predatory fish consume the smaller fish, which feed on zooplankton. Some introduced fish species, such as alewives, are subject to population variations due to temperature fluctuations; these variations may be reflected in zooplankton numbers. Zooplankton studies are difficult, because sampling must be frequent and identification and taxonomy are tedious and demanding specialties.

Studies in Lake Erie since the late 1920s have shown that zooplankton increase with eutrophication and then decline as nutrient pollution is controlled. Most studies have been conducted in the west basin. Two additional exotic species were noticed in the 1960s. In the 1980s, the spiny water flea Bythotrephes appeared; this is cause for concern.

Bythotrephes is more abundant in the offshore than in the nearshore, probably due to temperature preference or perhaps predation by alewife and gizzard shad. When alewife abundances are particularly low in Lake Ontario-as has been true in 1987, 1994, and 1995 (O. Johannsson, Department of Fisheries and Oceans Canada, personal communication)-Bythotrephes is able to increase its numbers. Bythotrephes eats other zooplankton and therefore competes directly against young-of-the-year fish. Preliminary studies indicate that between 10 percent and 40 percent of zooplankton production can be consumed by Bythotrephes. Bythotrephes is not a preferred prey for many fish. Thus, this new addition to the fauna is at best an extra trophic level between algae and fish; this means more inefficiency on energy transfer. At worst, Bythotrephes is an energy sink from the standpoint of fish production.

Zebra mussels seem to have affected zooplankton. The mussels, which spend most of their life attached to the lake bottom, divert energy to the benthic system and away from the plankton system that many fish have depended on. The mussels' immature planktonic stages can at times be as abundant as native zooplankton once were. Zooplankton abundance has decreased in Lake Erie's east basin, where there is the most extensive shallow-water substrate for zebra mussels. Changes in the biomass of zooplankton in the lake's west and central basins are less clear.

To some extent, the challenges to the zooplankton community seen in the lower lakes are present in all the lakes. In the last 13 years, the introduced species have changed the trophic relations in the lakes. Expectations of fish yield based on previous trophic structure may therefore not be realized.

Table 9. Mean Number (s.d.) per 35 cm² of 12 Taxa in Great Lakes Community Assemblages

Taxa	Comm. 1	Comm. 2	Comm. 3	Comm. 4	Comm. 5	Comm. 6
Chironomus spp.	5.7 (5.8)	(3.1)	(1.3)	(1.8)	0.0	(0.4)
Heterotrissocladius spp.	0.2 (1.1)	0.8 (2.5)	0.0	(0.7)	(1.7)	(1.8)
Procladius spp.	(1.9)	(2.3)	(2.7)	(1.4)	(0.3)	(0.6)
Diaporeia hoyi	0.0	(6.2)	(0.9)	0.0	(41.8)	(5.1)
Amnicola limosa	(0.3)	(1.2)	0.0	(0.7)	0.0	0.0
Valvata tricarinata	(0.4)	0.7 (1.9)	(0.2)	(2.0)	0.0	0.0
Dreissenia polymorpha	(7.7)	(1.0)	(0.6)	(78.1)	0.0	(0.7)
Dreissenia bugensis	(7.2)	0.0	0.0	(181.2)	0.0	0.0
Pisisdium casertanum	(2.8)	(8.7)	(1.8)	(0.8)	(8.4)	(1.1)
Stylodrilus heringianus	0.0	(1.8)	0.0	0.0	(8.9)	(3.8)
Aulodrilus pigueti	(0.7)	0.2 (0.6)	(0.7)	(0.4)	0.0	0.0
Helobdella stagnalis	0.2 (0.3)	0.0	0.0	0.3 (0.3)	0.0	0.0

Communities 1 and 4 largely represent sites in Lake Erie. Community 1 is characterized by chironomid midges, primarily Chironomus, and by the presence of Dreissenia. Community 4, which is represented by only nine Lake Erie sites, is dominated by zebra mussels (Dreissenia spp.).

Communities 2 and 3 are characterized by the sphaerid (fingernail) clam Pisidium; in Community 2, it is associated with the amphipod Diaporeia hoyi, and in Community 3 with the predatory midge Procladius. Communities 2 and 3 include the majority of Georgian Bay sites, together with sites from the North Channel, Lake Ontario, and Lake Erie. Communities 5 and 6 are both Diaporeia hoyi and Stylodrilus heringianus dominated. The primary difference between the two is quantitative: much larger numbers are found in Community 5 (which characterizes Lake Michigan) than in Community 6 (largely represents Lake Superior sites). These data show a strong spatial signal in the occurrence of communities at a large scale; however, each community occurs in a number of the lakes (Table 10), and there is no certainty of determining the assemblage of organisms expected at a site based on the lake. The overall correlation of habitat variables with community structure showed the following variables to relate to community structure: depth, latitude, longitude, alkalinity (overlying water), calcium oxide (sediment), total nitrogen (sediment), and total organic carbon (sediment). From these relationships, it is possible to develop models to predict the community expected at a site based on the site's environmental attributes.

Table 10. Occurrence of Six Community Types among 252 Great Lakes Reference Sites, and Number of Sites Representing Each Community

Lake	Community 1	Community 2	Community 3	Community 4	Community 5	Community 6
Erie	17	3	11	9	1	0
Ontario	7	6	9	0	2	4
St Clair	1	0	0	0	0	0
Huron	2	4	1	0	6	4
Georgian Bay	0	11	32	0	0	18
North Channel	2	8	11	0	1	14
Michigan	0	7	0	0	22	8
Superior	0	0	0	0	2	29

To use these data to establish impairment, it is necessary to know what type of community would be expected to occur at any site. This expected community type, based on the reference sites, can then be compared with the actual species occurring at a site to establish whether the predicted group of organisms is actually present. Because it is important to know what organisms would occur at a site if it were unaffected, it is necessary to use only certain environmental variables-those that would not be modified by anthropogenic activity. Accordingly, although they were measured at each site, we have not included nutrients, metals, or organic contaminants as potential predictors. A total of 26 variables have been examined for their ability to predict community assemblages, including major elements, particle size and organic content of the sediment, water depth and alkalinity, and site location (latitude and longitude).

Stepwise discriminant analysis shows that 11 variables can discriminate sites between the six community types with an error rate of 32.4 percent, predicting 162 of the 252 sites correctly. To verify this predictive model, 20 sites were removed from the reference data set; the model was then rebuilt using the 232 remaining sites. Using the 11 predictor variables identified by discriminant analysis, 16 of the 20 sites (80 percent) were correctly predicted (Table 11).

Table 11. Accuracy of Predicting Community Types at 20 Sites

Site membership	Predicted to
	Comm. 1	Comm. 2	Comm. 3	Comm. 4	Comm. 5	Comm. 6
Comm 1	2	0	0	0	0	0
Comm 2	0	3	0	0	0	0
Comm 3	1	2	3	0	0	0
Comm 4	0	0	0	1	0	0
Comm 5	0	0	0	0	3	0
Comm 6	0	0	0	1	1	4

7.2.3 Fish

The native fish fauna of the Great Lakes basin comprise 153 species-in 64 genera and 25 families-and is relatively large and diverse (Bailey and Smith 1981). Status and trend information are available for a number of fishes commonly found in the Great Lakes. The longest set of records is for fish species that were of commercial value and that entered the commercial catch. The commercial fishery in the Great Lakes dates back to the 1700s in some areas; regular reporting of the fishery began in 1867 in Canada and in 1879 in the United States (Baldwin et al. 1979). Because the records do not report the amount of fishing effort expended to catch the fish, or the amounts of some fish species that were caught but not brought to land for sale, they must be interpreted carefully. The records for the high-value, intensively fished species such as lake whitefish probably do reflect the trends in abundance, whereas records for low-value species such as freshwater drum do not. Freshwater drum were often taken incidentally in large numbers in nets set for other high-value species such as yellow perch and walleye. The market price for freshwater drum and the size of the catch of high-value species made by the individual fisherman on any given day probably determined how many freshwater drum were brought ashore for sale and how many were simply dumped back into the lake. Thus, the records for freshwater drum and other low-value species are generally not good indicators of trends in abundance. However, if the catch data are interpreted carefully, the history of the early commercial fishery in the Great Lakes can be seen to be one of intensive, selective fishing that eventually caused stocks of high-value species to decline and in some cases to become extinct. A more detailed discussion of the use of commercial catch data to examine the dynamics of commercially harvested Great Lakes fish is available elsewhere (USFWS 1995b).

Catch records for the lake sturgeon, blue pike, and walleye that inhabited the nearshore waters illustrate the effects of overfishing on coolwater species. The lake sturgeon, which does not reproduce until it is about 25 years old, was one of the first species to approach extinction in the Great Lakes. Annual catches in Lake Erie's U.S. waters fell from an all-time high of 2.1 million kg in 1885 to about 13,000 kg in 1917. Thereafter, reported catches never exceeded 10,000 kg, and after 1966 the catch fell to zero. Early in the fishery, the lake sturgeon was considered a nuisance species: it destroyed nets set for other smaller fish. Later, as markets developed, it became a sought-after species. The construction of dams that denied the lake sturgeon access to its spawning grounds in Great Lakes tributaries also helped accelerate its decline. The blue pike, a high-value species that reproduced at about age 4, became extinct because of overfishing. Annual catches as high as 9 million kg were made in the middle 1930s in Lake Erie's U.S. waters, but by the early 1960s the species had been fished to extinction. The walleye, a closely related species, was also severely overfished in Lake Erie. Catches declined from highs of about 2.3 million kg to 2.8 million kg annually in the late 1940s through the late 1950s, and to about 25,000 kg in 1971. Commercial fishing interests generally attributed the decline to deteriorated environmental conditions. However, closure of the fishery due to mercury contamination in the early 1970s followed by the imposition of more stringent catch regulations allowed walleye numbers to rapidly increase; now, the species again supports a healthy, self-sustaining, high-value fishery.

High-value coldwater fishes that use the nearshore waters during the colder months of the year declined to virtual extinction in all or some of the Great Lakes; these species include the lake trout, lake whitefish, and lake herring. Native populations of lake trout were nearly extinguished in the Great Lakes as a combined result of overfishing and predation by the introduced sea lamprey. The native lake trout populations in Lakes Michigan, Erie, and Ontario were lost; only a small population survived in a remote area of Lake Huron's Georgian Bay. In Lake Superior, the nearshore populations of native fish were sharply reduced by the late 1950s, when commercial fishing ended and the sea lamprey was controlled. Lake whitefish populations reached record lows in the 1950 and 1960s in Lake Huron, and in the 1950s in Lake Michigan, but have since recovered. In Lake Erie, for example, the U.S. catch fell gradually from a high of 17.8 million kg in the late 1800s to zero in the early 1960s, but a recovery may have begun in the late 1980s. Catches also fell to record lows in Lake Superior in the 1970s. These declines in the lake herring populations have been attributed to overfishing and to predation on young lake herring by rainbow smelt.

Overfishing has also contributed to a loss in the genetic diversity of the native fish fauna of the Great Lakes. This shift includes the loss associated with the extinction of several native species, including the blue pike and some deepwater ciscoes (whitefishes), as well as the loss of genetic diversity resulting from the extirpation of local stocks of native fishes by overfishing, together with habitat loss and the introduction of exotic species. Although the loss due to species extinctions is relatively obvious and unequivocal, the loss due to the extirpation of local stocks is less so. Perhaps the best examples can be seen among the whitefishes and lake trout, which were major elements of the native coldwater fish fauna of the Great Lakes.

At the time of European settlement, whitefishes were abundant and ecologically important as food for lake trout and burbot and as human food. As many as 40 species and subspecies of ciscoes (whitefishes most closely related to the lake herring) were identified by biologists working in the basin. Most of the group probably evolved locally, because there are no records for any of them, other than the lake herring, from outside the basin. Bailey and Smith (1981) present evidence that the reproductive isolation (absence of interbreeding) that had developed among these species and subspecies over a 10,000-year period was unstable and that it broke down as populations were reduced by commercial fishing and predation by the sea lamprey. Interbreeding among the survivors then caused their offspring to become more alike genetically. Today the ciscoes are represented only by the lake herring and by one to three other closely related species or subspecies that are extinct, are approaching extinction, or are simply merging their genetic identities by interbreeding.

Differences were historically recognized among stocks of native lake trout by aboriginal people, explorers, and missionaries, and later by naturalists and biologists (Krueger and Ihssen 1995); the evolution of subspecies was postulated for lake trout in the Finger Lakes in the Lake Ontario drainage of New York State (Royce 1951) and in the Great Lakes proper (Brown et al. 1981; Goodier 1981; Goodyear et al. 1982). Most of the native stocks recognized historically in Lake Superior and all of those in the four lower Great Lakes, except for two small relict native stocks in Lake Huron, were lost before they could be examined for genetic differences. However, genetic differences have been demonstrated among the native lean, humper, and siscowet lake trout groups that survive in Lake Superior (Krueger and Ihssen 1995); similar differences must have occurred in the other Great Lakes, where lake trout occupied a diversity of habitats.

The loss of native genetic diversity affects the status of the Great Lakes ecosystem irreversibly. Left unoccupied were habitats, particularly those in deep water, that were occupied productively by native species and stocks that had become adapted to them following the retreat of the glaciers from the basin about 10,000 years ago. Other vacated habitats in shallower water were left open to invasion by undesirable exotic species that had gained access to the basin as a result of human activities. The full and productive use of the diverse array of habitats in the Great Lakes nearshore waters requires that the genetic diversity of the remaining native species be protected by actions taken to perpetuate all recognized stocks of these species.

Contemporary information on the status and trends of Great Lakes fish populations is now compiled annually for each of the lakes by committees that comprise biologists and managers from the Great Lakes states, the province of Ontario, Canada's Department of Fisheries and Oceans, the National Biological Service, and the Indian tribes that have treaty fishing rights. These reports reveal the following major trends.

In Lake Superior, the lake trout fishery is currently maintained by stocking and by natural reproduction from wild fish (Hansen 1994). Introduced species of trout and salmon support a stable fishery, whereas brook trout and lake sturgeon populations have not recovered from earlier declines and are still at low levels. Lake herring numbers are recovering strongly, and rainbow smelt are reduced from earlier levels of peak abundance. Lake whitefish are abundant and support a productive fishery. The sea lamprey is reduced to about 10 percent of its former peak abundance, and the ruffe is increasing in abundance.

In Lake Huron, the fish community is recovering, but remains unstable after decades of overharvest and the effects of introduced species (Ebener et al. 1995). Modest numbers of stocked lake trout are once again reproducing in the lake, and populations of whitefish are more abundant than at any other time in the century. Walleye and yellow perch are once again abundant. Rainbow smelt and alewife populations are stable but have been reduced compared to former peak levels in the 1970s. In the 1980s, the sea lamprey increased in abundance in the northern end of the lake, imposing high mortality on lake trout and reversing recent gains in lake trout restoration in that area.

In Lake Michigan, substantial numbers of stocked, breeding-age lake trout are present in lake trout refuges at several locations throughout the lake (Holey et al. 1995). Spawning and fry production by stocked fish have been recorded at several locations in the lake; wild yearling and older lake trout have also been found in the lake, but substantial numbers of adult wild fish have not been produced. Pacific salmon abundance is sharply reduced compared to the peak levels reached in the 1970s to the middle 1980s. The causes for that decline are complex and not fully understood. Mortality of coho salmon fry soon after hatching has been observed. This mortality can be alleviated by treatment with vitamin B₁, suggesting that there is a vitamin B₁ deficiency in the female parent that causes mortality in the fry. Mortality of adult Pacific salmon in the lake is correlated with an incidence of bacterial kidney disease, a pathogen that has been introduced to the Lake Michigan basin. A linkage between the pathogen's virulence and the salmon's nutritional status is being investigated. The biomass (a measure of abundance expressed as weight) of each of the three major prey fishes in Lake Michigan has changed significantly since the early 1970s (National Biological Service, unpublished data). Alewives constituted more than 80 percent of the biomass in catches in the 1970s but declined to about 10 percent in the middle 1980s through the 1990s. The biomass of rainbow smelt decreased from between 15 percent and 20 percent in the 1970s and early 1980s to less than 10 percent in the middle 1980s and 1990s. Slimy sculpin abundance peaked in the late 1970s, but declined in the 1980s and 1990s to less than 20 percent of peak 1970s levels, probably in response to predation by trout, salmon, and burbot.

In Lake Erie, lake trout restoration goals are being met, and lake whitefish are showing signs of a recovery (GLFC 1995a). Walleye and yellow perch are intensively managed to provide productive recreational and commercial fisheries in the United States and Canada (GLFC 1995b). The abundance of the major forage fish species in Lake Erie-rainbow smelt, spottail shiners, emerald shiners, gizzard shad, and alewives-may be declining.

In Lake Ontario, the fish community has improved considerably from a low point in the 1960s (Kerr and LeTendre 1991; OMNR and NYSDEC 1994). Alewife and rainbow smelt abundance declined in the 1980s in response to (a) trout and salmon predation and (b) reduced nutrient input to the lake; in the 1990s, stocking of trout and salmon was reduced to bring them into better balance with their food supply. Some native fishes are recovering from low levels observed in the 1960s. For example, lake whitefish, which typically were most abundant in the eastern end of the lake, were nearly absent there in the catch in the 1970s, began increasing in 1980s, and were 30- to 40-fold more abundant there in the 1990s.

Fish from Great Lakes nearshore waters in areas where the sediment is contaminated sometimes exhibit tumours (Baumann et al. 1996). These tumours fall into two general classes: benign (or harmless) and malignant (or cancerous). It is generally believed that tumour production may be a response to degraded habitat. Tumour outbreaks in the Great Lakes have been found in populations of benthic species, including brown bullhead, white sucker, common carp, bowfin, and freshwater drum. Common carp-and particularly common carp ´ goldfish hybrids-primarily exhibit gonadal tumours; freshwater drum primarily have neural (chromatophore) tumours that are externally visible. Bowfin liver neoplasms (newly formed tumours that may or may not become cancerous and that are not readily seen as a lump or bump) have been documented in fish taken from the Detroit River. White sucker and brown bullhead both exhibit skin and liver neoplasms. These species have been more studied than the others in the Great Lakes. The white sucker has been used as an indicator organism for a series of contaminant studies in Canada. Similarly, the brown bullhead has been used as an indicator organism for a variety of studies in the United States. Many of the locations in which tumour outbreaks in these species were documented have subsequently been designated as Areas of Concern by the International Joint Commission.

Epidermal (skin) papillomas (tumours that appear as raised lumps or bumps and will become cancerous), particularly on the lips, are the most commonly observed neoplasm in white sucker. Recent experimental work by Premdas and Metcalf (1996) has proven that papillomas can be induced in white suckers by exposing them to a cell-free filtrate obtained from enlarging papillomas. This result indicates that a virus is involved in producing these tumours. Widespread surveys in Canada (Figure 22 and Table 12) revealed the presence of skin neoplasms in white sucker populations throughout the Great Lakes. However, a high prevalence (more than 20 percent) of lip papillomas occurred only in populations from the lower Great Lakes, and an especially high prevalence of oral papillomas was found only in such locations as Hamilton Harbour and Oakville Creek, Ontario, where the sediment was polluted with industrial wastes. Thus, epidermal papillomas may result from both virus and chemical carcinogens in the sediment.

Epidermal papillomas are also found on brown bullhead in a number of Great Lakes locations (Figure 23 and Table 13). The greatest incidence of such tumours was in populations from Hamilton Harbour and Presque Isle Bay, where frequencies exceeded 50 percent-more than double the next highest values (Obert 1994; Smith et al. 1989). Populations in the Buffalo and Black Rivers formed a second cluster, with papilloma prevalence of about 25 percent. The four sites just mentioned are all locations with elevated levels of PAH in the sediment; all have also been designated as Areas of Concern. Other Great Lakes locations surveyed had bullhead populations with papilloma incidence ranging from 2 percent to 16 percent. These included a mixture of contaminated sites (e.g., Ohio's Ashtabula River, at 16 percent) and uncontaminated sites (e.g., Ontario's Long Point Bay, at 15 percent). The percentage of squamous carcinomas (malignant skin cancers) was seldom determined; Presque Isle Bay, however, had an extremely high prevalence of these, with fish from the Cuyahoga River and Hamilton Harbour also having elevated frequencies. Though a virus may be involved in producing these cancers, no experimental evidence supports such a conclusion at this time. Sediment carcinogens do seem to have a role in producing these cancers.

Table 12. Prevalence of Lip and Body Papillomas Reported in White Sucker Populations in Ontario Waters of the Great Lakes and in Surrounding Areas

Location	Collection Date	N	Neoplasms (%)	Referencea
Hamilton Harbourb	1972-75 1981-83 1986	- 168 225	30 39 43	1 2 3
Oakville Ck.b	1982-83 1986	612 482	62 46	2 3
Bay of Quinteb	1982-83	148	5	2
Keefers Ck.b, c	1986	81	11	3
Whites Ck.., L.b, c	1986	71	16	3
Thunder Bay	1986	199	2.5	4
Jackfish Bay	1987	300	7.6	4
St. Marys River	1988	185	9.1	4
Black Bayc	1986	232	3.4	4
Mountain Bayc	1987	304	3.6	4
Batchawana Bayc	1988	231	8.6	4
Ganaraska Riverb	1992-93	356	46	5
Squaw Riverb, c	1992-93	239	5	5

Source: Adapted from Baumann et al. 1996.

^a Key to References in Column 5: (1) Sonstegard et al. 1977; (2) Cairns and Fitzsimons 1988; (3) Smith et al. 1989a; (4) Smith, unpublished; (5) Premdas et al. 1995.[[POST: No Refs for any of these people in list at back. TAE didn't have time to find. He'll try to fix after conference.]]

^b Only data for lip papillomas are reported.

^c Reference site from a relatively pristine area.

Table 13. Prevalence of External Tumours Reported in Brown Bullhead Populations in U.S. and Canadian Waters of the Great Lakes Basin

Location	Collection Date	N	Neoplasms (%)	Malignancies (%)	Referencea
Ashtabula River, OH	1991	97	16.0	NAb	1
Black River, OH	1993	104	25.0	NA	2
Buffalo River, NY	1988	100	23.0	NA	2
Plum Creek, MI	1985	57	7.0	NA	2
Cuyahoga River, OH	1984	90	8.9	5.5	3
Menominee R., WI and MI	1984	47	2.1	NA	3
Fox River, WI	1984	52	7.7	1.9	3
Detroit River, MI	1985-87	449	10.0	NA	4
Hamilton Harbour, ON	1985	176	55.0	7.0	5
Presque Isle Bay, PA	1992	102	56.0	33.0	6
Long Point Bay, ONc	1985	53	15.0	NA	5
Munuscong Bay, MIc	1984	63	3.2	NA	3
Old Woman Ck., OHc	1984-85	120	2.5	NA	2

Source: Adapted from Baumann et al. 1996.

^a Key to References in Column 5: (1) Mueller and Mac 1994; (2) Baumann, unpublished; (3) Baumann et al. 1991; (4) Maccubbin and Ersing 1991; (5) Smith et al. 1989a; (6) Obert 1994.[[POST: TAE will try to get these Refs, so we can add them to Refs list at back.]]

^b "NA" means that brown bullheads from that site have not been analysed histologically for malignancies.

^c Reference site in relatively pristine area.

Though white suckers from 19 different locations in Canada were examined for liver tumours, no population had an incidence as great as 10 percent (Table 14 and Figure 22). White suckers in five of seven relatively pristine reference sites had a liver tumour prevalence of less than 0.5 percent. However, white suckers from nine Areas of Concern sampled had an average prevalence of 5.3 percent. Lake Superior's Batchawana Bay (Ontario) was the only relatively pristine reference location where bullhead had a tumour prevalence (8.6 percent) that exceeded 3 percent; this high prevalence may reflect the advanced age (up to 26 years) of the suckers that were examined from the bay. A high incidence of liver tumours occurred among suckers older than age 15 (23 percent) from this location. The cause of liver tumours in white sucker is probably associated with exposure to carcinogenic contaminants; tumour prevalence of 5 percent or greater should be viewed as an indication of such exposure.

Brown bullhead collected from a series of locations with industrial contamination had liver tumours (Table 15 and Figure 23). Bullhead from two relatively uncontaminated sites had a liver tumour prevalence that was greater than 5 percent, though these populations had a greater percentage of older fish(age 5 and up) than the industrial sites (Baumann et al. 1996). Bullhead from the Cuyahoga and Detroit Rivers had tumour prevalence of between 8 percent and 10 percent, while those from the Buffalo River and Presque Isle Bay had about 20 percent. All four of these river systems have elevated levels of polynuclear aromatic hydrocarbons (PAH) in at least some portions of their sediment. In 1982, when a coking facility associated with a steel plant on Ohio's Black River was operational, the bullhead population had a liver cancer prevalence of 38.5 percent (Table 14). The coking facility closed in l983, and by l987 PAH concentrations in surficial river sediment had declined to 0.4 percent of the concentration in 1980 (Baumann and Harshbarger 1995). By 1987, the cancer frequency in the bullhead population had also declined-to about one-fourth of that seen in l982. Areas of sediment most contaminated with PAH were subsequently dredged from the river in 1990, and two years later the cancer incidence in bullhead exceeded that in 1982 (Table 14). This Black River case history indicates that natural, unassisted remediation can be effective in reducing the incidence of cancer in bullheads in some systems; it also shows that dredging using traditional methodology can result in at least a temporary increase in cancer incidence and degradation of the health of native species (Baumann and Harshbarger 1995). Collectively, these data show that bullhead liver tumours track PAH levels in natural systems, making them a good biomarker for exposure of benthic fish to carcinogens in sediment.

Figure 22. White Sucker Tumour Surveys

Table 14. Prevalence of Combined Cholangiocytic (Bile-duct) and Hepatocytic (Liver-cell) Liver Tumours Reported in White Sucker Populations at Remedial Action Plan (RAP) Sites and Reference Sites in Canadian Waters of the Great Lakes, and from Sites in Surrounding Areas

Location	Collection Date	N	Neoplasms (%)	Referencea
Hamilton Harbourb	1982-83	168	1.2	1,2,4
(Grindstone Ck.)	1985-90	119	5.8	3,4
Oakville Ck.	1982-83 1985-90	612 306	7.4 8.1	1,2,4 3,4
Spencer Ck.b	1982-83	174	3.4	2,4
Forty Mile Ck.	1982-83	133	0	2,4
Rouge River	1982-83	199	3.5	2,4
Humber Riverb	1982-83	192	4.7	2,4
Bay of Quinteb	1982-83 1985-90	148 91	0.7 0	1,2,4 4
Ganaraska Riverb	1982-83	116	6.0	2,4
Cornwallb	1985-90	178	6.1	4
South Bayc	1982-83	228	0	1,2,4
Lake Nipissingc	1985-90	231	0.4	4
Whites Ck.c	1985-90	24	0	3,4
Keefers Ck..c	1985-90	37	0	3,4
Jackfish Bay b	1985-90	194	7.1	4
Kaministiquiab	1985-90	112	7.1	4
St. Marys Riverb	1985-90	184	9.2	4
Black Bayc	1985-90	231	0	4
Mountain Bayc	1985-90	75	2.4	4
Batchawana Bayc	1985-90	230	8.6	4

SOURCE: Adapted from Baumann et al. 1996.

^a Key to References in Column 5: (1) Cairns and Fitzsimons 1988; (2) Canada 1991; (3) Hayes et al. 1990; (4) Smith et al. 1995.[[POST: TAE will try to get these Refs so we can add them to Refs list at back; he didn't have time before.]]

^b RAP site on Great Lakes.

^c Reference site from a relatively pristine area.

Figure 23.Brown Bullhead Tumour Surveys

Table 15. Prevalences of Liver Tumours Reported in Brown Bullhead Populations in U.S. and Canadian Waters of the Great Lakes Basin

Location	Collection Date	N	Neoplasms (%)	Malignancies (%)	Referencea
Ashtabula River, OH	1991	97	6.2	3.1	1
Black River, OH	1982 1987 1992	124 80 97	60.0 32.5 58.0	38.5 10.0 48.0	2 2 3
Buffalo River, NY	1988	100	19.0	5.0	3
Cuyahoga River, OH	1984	85	9.4b	NA	4
Detroit River, MI	1985-87	306	8.8	NA	5
Hamilton Harbour, ON	1984	124	1.6	1.6	6
Presque Isle Bay, PA	1992	102	22.0	6.9	7
Old Woman Ck., OHc	1992-93	125	5.6	3.2	3
Munuscong Bay, MIc	1984	63	5.9	2.9	4

SOURCE: Adapted from Baumann et al. 1996.

^a Key to References in Column 5: (1) Mueller and Mac 1994; (2) Baumann and Harshbarger 1995; (3) Baumann, unpublished; (4) Baumann et al. 1991; (5) Maccubbin and Ersing 1991; (6) Smith et al. 1989a; (7) Obert 1994.

^b Conservative value based on a combination of gross observations and a limited histopathological survey.

^c Reference site in relatively pristine area.

Joint Canada-U.S. studies of benthic fishes in a gradient of polluted to pristine Great Lakes locations using standardized methodology would greatly enhance our knowledge of the etiology of tumours and their usefulness as indicators.