Grass pickerel (Esox americanus vermiculatus) COSEWIC assessment and status report: chapter 10

Limiting factors and threats

Changes resulting from urban development create habitats less suitable than those in creeks, which flowed previously through agricultural settings. Silting of streams by the activity of cattle can be damaging. In areas surrounding presently known populations, clearing emergent and submergent vegetation from streams, ponds connected to streams, or quiet bays of larger bodies of water would reduce suitable habitat and prevent the expansion of the range of the grass pickerel. Failure of year classes has been traced to declining water levels stranding fingerlings and adults in nursery areas (Kleinert and Mraz 1966). Becker (1983) cited winter mortality associated with the low oxygen levels in reduced water depth; although Cooper and Washburn (1949) indicated tolerance for oxygen levels of 0.3-0.4 ppm. The major threat is the destruction and degradation of wetland habitat. Foster (1979) found that increases in turbidity had a negative impact on grass pickerel feeding in Long Point Bay.

Yagi (2004) noted the following: “The Department of Fisheries and Oceans have classified drains that do not flow year round as type F habitat. This means that drain maintenance can occur when the drain is not flowing. Pool habitat where this species is residing over the summer is greatly affected by this practice”. Presumably the water level in the pool, and therefore the available habitat for grass pickerel, would be reduced when this drain maintenance occurs. In Ohio, Trautman (1981) indicated that the grass pickerel decreased in number or became extirpated wherever ditching, dredging, or other forms of channelization destroyed its habitat.

The redfin pickerel is now known from Contrecoeur, Quebec, a distance of approximately 57 km from Lac St-Louis. If it disperses upstream into Lac St-Louis, it may hybridize with or replace the grass pickerel (P. Dumont pers. comm.), if it still occurs there.

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