. The Canadian field-naturalist. The Crayfish, Orconectes virilis, as an Indicator of Mercury Contamination Kees Vermeer Canadian Wildlife Service, Edmonton, Alberta Abstract. The crayfish, Orconectes virilis, is a good indicator of mercury contamination in different water bodies. Crayfish muscle contained three times as much mercury as the remaining body. Mercury levels did not differ significantly in samples collected from various parts of the shore of a highly contaminated lake. Introduction Surveys of mercury residues in fish and fish- eating birds have been conducted in Canada by BUgh (19
. The Canadian field-naturalist. The Crayfish, Orconectes virilis, as an Indicator of Mercury Contamination Kees Vermeer Canadian Wildlife Service, Edmonton, Alberta Abstract. The crayfish, Orconectes virilis, is a good indicator of mercury contamination in different water bodies. Crayfish muscle contained three times as much mercury as the remaining body. Mercury levels did not differ significantly in samples collected from various parts of the shore of a highly contaminated lake. Introduction Surveys of mercury residues in fish and fish- eating birds have been conducted in Canada by BUgh (1970), Fimreite et al. (1971), Ver- meer (1971) and Wobeser et al. (1970). As both fish and fish-eating birds migrate over large areas, they may be less reliable for pin- pointing local mercury contamination than aquatic invertebrates which migrate to a lesser extent. The crayfish, Orconectes virilis, which lives under stones in both lakes and rivers, was investigated as an indicator of mercury con- tamination because this aquatic invertebrate feeds on detritus and scavenges on fish, is more restricted in its movements than fish and is the most widely distributed crayfish species in Canada (Figure 1). Methods O. virilis samples were collected in Manitoba from the mouth of the Saskatchewan River (53°10'N, 99°16'W) at Grand Rapids, and from Lake Winnipegosis (52°53'N, 99°47'W) at Denbeigh Point during the last half of June and the first half of July, 1971. In western On- tario they were collected from Clay Lake (50° 03'N, 93°30'W), seven miles north of Quibell, during the first half of August, 1971. Those crayfish sampling locations were selected be- cause they represented a range from low (Lake Winnipegosis) to very high (Clay Lake) mer- cury levels reported in fish (Bligh, 1970). In- asmuch as Clay Lake is known to be among the most mercury-contaminated water bodies in Canada, eight sampling stations were estab- lished there (Figure 2) to determine to what extent mercury le
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