Raised black lesions observed in 30 percent of the brown bullhead collected from two sites in Lake Memphremagog from 2014 through 2017 were identified microscopically as malignant melanoma. Malignant melanoma in freshwater fishes has been reported before, but this cancer occurrence cluster is raising questions about the cause of the tumors and the implications for the long-term health of fish populations. Previous findings and histopathology characteristics measured in this study suggest that tumor development is likely associated with multiple environmental and genetic factors. Study designs are being developed to test these hypotheses.
In 2012, brown bullhead (Ameiurus nebulosus) with large, raised, black growths were first reported from multiple areas within the Vermont portion of Lake Memphremagog. The natural lake is 1,780 square kilometers and lies within the boundaries of Vermont, United States and Quebec, Canada. The lake is important for recreational activities and is a major drinking water supply for Canadian municipalities. Bullhead and other fish can be caught in the lake from spring through fall for consumption. Melanoma, a melanocyte-derived neoplasm, has been reported in a variety of wild fishes, including brown bullhead; however, the prevalence and pathology of the growths observed in the brown bullhead in Lake Memphremagog were unknown.
Therefore, U.S. Geological Survey (USGS) scientists, in collaboration with Vermont Fish and Wildlife Department, began a study to document the prevalence of the visible lesions in surveys conducted in 2014–17 and to describe the gross and microscopic pathology findings observed in affected bullhead.
Surveys conducted from 2014 to 2017 at two sites within the lake indicated an overall prevalence of 30 percent in adult brown bullhead with a total length of 200 millimeters and above. There were only slight differences in prevalence between the sites: Hospital Cove (361 total fish collected; 29 percent affected) and South Bay (231 total fish collected; 33 percent affected). These lesions ranged from slightly raised, smooth black areas to large, nodular areas on the body surface and fins and within the oral cavity.
To determine the pathology of the lesions, subsequent microscopic analyses were completed on 20 bullhead with black lesions and 20 normal-appearing bullhead collected from Lake Memphremagog and 10 normal-appearing bullhead from Ticklenaked Pond without any lesions.
The raised black lesions observed in brown bullhead collected from two sites in Lake Memphremagog were identified microscopically as malignant melanoma with invasion into surrounding hypodermis, skeletal muscle, and bone as well as metastases to gill, ovary, and intestine. Liver neoplasms, including cholangiocarcinoma and hepatic cell carcinoma, were observed in 8 percent of the Lake Memphremagog bullhead. Neither skin nor liver neoplasms were noted in Ticklenaked Pond, a site used for comparison. Melanoma prevalence in this study was also greater than observed for bullhead collected during 2011 to 2013 at sites in Lake Erie and Lake Ontario watersheds during a previous study where the prevalence of melanoma in bullhead was rare .
There have been reports of malignant melanoma epizootics in freshwater fishes, but they are rare and the cause of this tumor outbreak is currently unknown. Genetic factors, ultraviolet radiation, chemical contaminants, and viral pathogens alone or in combination may be linked to tumor incidence. Chemical analyses of skin, water, and sediment; measurement of ultraviolet radiation in brown bullhead habitat; and molecular analyses to identify viral sequences or mutations are logical next steps to identify the associated risk factors.
Scientists on the USGS Fishing and Hunting and Immunomodulation Science Teams are continuing to develop and test hypotheses to address key questions about the interactions between pathogen and toxicant exposures and tumor development in fishes. Identification of the actual risk factors is important to prioritize mitigation and minimize risk to fish, wildlife, and humans.
This study was supported by the Vermont Fish and Wildlife Department and the USGS’s Environmental Health Programs (Contaminant Biology and Toxic Substances Hydrology); the USGS Cooperative Fish and Wildlife Research Unit and Fisheries Programs.
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Below are publications associated with this featured science activity.
Malignant melanoma of Brown Bullhead (Ameiurus nebulosus) in Lake Memphremagog, Vermont/Quebec
Assessment of skin and liver neoplasms in brown bullhead (Ameiurus nebulosus) collected at the Ashtabula River Area of Concern and associated reference site, Ohio, in 2016
Assessment of the fish tumor beneficial use impairment in brown bullhead (Ameiurus nebulosus) at selected Great Lakes Areas of Concern
- Overview
Raised black lesions observed in 30 percent of the brown bullhead collected from two sites in Lake Memphremagog from 2014 through 2017 were identified microscopically as malignant melanoma. Malignant melanoma in freshwater fishes has been reported before, but this cancer occurrence cluster is raising questions about the cause of the tumors and the implications for the long-term health of fish populations. Previous findings and histopathology characteristics measured in this study suggest that tumor development is likely associated with multiple environmental and genetic factors. Study designs are being developed to test these hypotheses.
Raised black external tumors on adult brown bullhead (Ameiurus nebulosus) collected from Lake Memphremagog (Vermont and Canadian Border) were identified as malignant melanoma in a 2014–17 study. In 2012, brown bullhead (Ameiurus nebulosus) with large, raised, black growths were first reported from multiple areas within the Vermont portion of Lake Memphremagog. The natural lake is 1,780 square kilometers and lies within the boundaries of Vermont, United States and Quebec, Canada. The lake is important for recreational activities and is a major drinking water supply for Canadian municipalities. Bullhead and other fish can be caught in the lake from spring through fall for consumption. Melanoma, a melanocyte-derived neoplasm, has been reported in a variety of wild fishes, including brown bullhead; however, the prevalence and pathology of the growths observed in the brown bullhead in Lake Memphremagog were unknown.
Therefore, U.S. Geological Survey (USGS) scientists, in collaboration with Vermont Fish and Wildlife Department, began a study to document the prevalence of the visible lesions in surveys conducted in 2014–17 and to describe the gross and microscopic pathology findings observed in affected bullhead.
Surveys conducted from 2014 to 2017 at two sites within the lake indicated an overall prevalence of 30 percent in adult brown bullhead with a total length of 200 millimeters and above. There were only slight differences in prevalence between the sites: Hospital Cove (361 total fish collected; 29 percent affected) and South Bay (231 total fish collected; 33 percent affected). These lesions ranged from slightly raised, smooth black areas to large, nodular areas on the body surface and fins and within the oral cavity.
To determine the pathology of the lesions, subsequent microscopic analyses were completed on 20 bullhead with black lesions and 20 normal-appearing bullhead collected from Lake Memphremagog and 10 normal-appearing bullhead from Ticklenaked Pond without any lesions.
Photomicrograph showing melanoma on a fin of a brown bullhead fish. In the upper right-hand part is normal skin (epidermis). The epidermis has large clear cells and a layer of normal melanocytes along the basement membrane of the epidermis, which is where they normally are located. Most of the rest of the tissue is composed of neoplastic melanocytes that invade up into the epidermis as well as into the dermal and subdermal areas. The raised black lesions observed in brown bullhead collected from two sites in Lake Memphremagog were identified microscopically as malignant melanoma with invasion into surrounding hypodermis, skeletal muscle, and bone as well as metastases to gill, ovary, and intestine. Liver neoplasms, including cholangiocarcinoma and hepatic cell carcinoma, were observed in 8 percent of the Lake Memphremagog bullhead. Neither skin nor liver neoplasms were noted in Ticklenaked Pond, a site used for comparison. Melanoma prevalence in this study was also greater than observed for bullhead collected during 2011 to 2013 at sites in Lake Erie and Lake Ontario watersheds during a previous study where the prevalence of melanoma in bullhead was rare .
There have been reports of malignant melanoma epizootics in freshwater fishes, but they are rare and the cause of this tumor outbreak is currently unknown. Genetic factors, ultraviolet radiation, chemical contaminants, and viral pathogens alone or in combination may be linked to tumor incidence. Chemical analyses of skin, water, and sediment; measurement of ultraviolet radiation in brown bullhead habitat; and molecular analyses to identify viral sequences or mutations are logical next steps to identify the associated risk factors.
Scientists on the USGS Fishing and Hunting and Immunomodulation Science Teams are continuing to develop and test hypotheses to address key questions about the interactions between pathogen and toxicant exposures and tumor development in fishes. Identification of the actual risk factors is important to prioritize mitigation and minimize risk to fish, wildlife, and humans.
This study was supported by the Vermont Fish and Wildlife Department and the USGS’s Environmental Health Programs (Contaminant Biology and Toxic Substances Hydrology); the USGS Cooperative Fish and Wildlife Research Unit and Fisheries Programs.
- Science
USGS science related to this featured science activity.
Fishing and Hunting Integrated Science Team
The Fishing and Hunting integrated science team focuses on contaminant and pathogen exposures in the environment that could impact the presence and vitality of fish and wildlife populations that drive commercial, recreational and subsistence activities such as hunting and fishing. If actual risks are identified this project will inform how to economically and effectively minimize risk by providing...Immunomodulation Science Team
The Immunomodulation Integrated Science Team focuses on contaminant and pathogen exposures in the environment that might influence the immune systems of wildlife and the connection to their shared environment with humans. In collaboration with public-health officials, the Team also addresses potential human-health risks stemming from similar exposures. If actual risks are identified, this Team...Intersex in Male Smallmouth Bass in the Missisquoi River in Vermont: Understanding Factors that Can Lead to Endocrine Disruption in Field Settings
The presence of testicular oocytes (intersex) in male smallmouth bass (Micropterus dolomieu) in the Missisquoi River in Vermont varied over the period of the study and was not related to concentrations of known endocrine disrupting chemicals in the River. Although previous studies have shown linkages between endocrine disrupting chemical exposures and intersex in fish, these results indicate that...No Adverse Reproductive Effects Observed in Tree Swallows Exposed to Perfluoroalkyl Substances in Clarks Marsh, Michigan
Perfluoroalkyl substance (PFAS) concentrations in tree swallows (Tachycineta bicolor) breeding at Clarks Marsh near a decommissioned U.S. Air Force base in Michigan were among the highest concentrations ever documented in birds indicating significant PFAS exposures. In contrast to previous studies where reproductive impairment was documented at lower PFAS exposure, there were no adverse effects on...Sublethal Effects of Contaminants in Aquatic Food Webs—Research Challenges and Considerations for Future Studies
U.S. Geological Survey (USGS) and academic scientists partnered to identify challenges and provide considerations for future scientific study designs to advance our understanding of the often subtle sublethal effects of contaminants on individuals, populations, communities, and entire aquatic food webs.Long-term Studies Examine Contaminant Exposure and Reproduction of Ospreys Nesting in Two Large United States Estuaries
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The Fishing and Hunting integrated science team focuses on contaminant and pathogen exposures in the environment that could impact the presence and vitality of fish and wildlife populations that drive commercial, recreational and subsistence activities such as hunting and fishing. If actual risks are identified this project will inform how to economically and effectively minimize risk by providing...Body Symmetry in Forster's Terns Related to Mercury Exposure
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The incidence of particular skin and liver tumors on white suckers collected from some Wisconsin rivers corresponded to the degree of urban development within the watershed. Further research is needed to understand the relationship between exposure to urban-sourced contaminants and the initiation, promotion, and potential for population-level effects of these tumors. - Publications
Below are publications associated with this featured science activity.
Malignant melanoma of Brown Bullhead (Ameiurus nebulosus) in Lake Memphremagog, Vermont/Quebec
In 2012, brown bullhead (Ameiurus nebulosus) with large, raised, black growths were first reported from multiple areas within the Vermont portion of Lake Memphremagog. Subsequent surveys conducted from 2014 to 2017 at two sites within the lake indicated a prevalence of 30% in adult brown bullhead 200 mm and above total length. These lesions ranged from slightly raised smooth black areas to large nAuthorsVicki S. Blazer, Cassidy H. Shaw, Cheyenne R. Smith, P Emerson, Thomas R. JonesAssessment of skin and liver neoplasms in brown bullhead (Ameiurus nebulosus) collected at the Ashtabula River Area of Concern and associated reference site, Ohio, in 2016
Brown bullhead (Ameiurus nebulosus) is a commonly used indicator species for tumor surveys at Great Lakes Areas of Concern. The “fish tumors or other deformities” is one of the beneficial use impairments at the Ashtabula River Area of Concern. In May 2016, 150 brown bullhead were collected in the lower Ashtabula River and 150 were collected in the nearby Conneaut Creek as a reference. Length, weigAuthorsVicki S. Blazer, Heather L. Walsh, Ryan P. BrahamAssessment of the fish tumor beneficial use impairment in brown bullhead (Ameiurus nebulosus) at selected Great Lakes Areas of Concern
A total of 878 adult Brown Bullhead were collected at 11 sites within the Lake Erie and Lake Ontario drainages from 2011 to 2013. The sites included seven Areas of Concern (AOC; 670 individuals), one delisted AOC (50 individuals) and three non-AOC sites (158 individuals) used as reference sites. These fish were used to assess the “fish tumor or other deformities” beneficial use impairment. Fish weAuthorsVicki Blazer, Patricia M. Mazik, Luke R. Iwanowicz, Ryan P. Braham, Cassidy M. Hahn, Heather L. Walsh, Adam J. Sperry