Grass pickerel (Esox americanus vermiculatus) COSEWIC assessment and status report: chapter 7

Habitat

Habitat requirements

The usual habitat is water of neutral or slightly basic nature, clear to tea coloured, with very slow to no flow, generally shallower than 2 m, with abundant to dense submerged, floating and emergent aquatic vegetation. Range of pH in Ontario habitats was 6.26-8.32 (Scott and Crossman 1973). Ming (1968) reported grass pickerelfrom fast-flowing mountain streams. The vegetative composition is similar to that in which the other pickerels, northern pike, and muskellunge are found, which includes representatives of Potamogeton, Ceratophyllum, Nymphaea, Nuphar and Chara. Complete floral lists of grass pickerel habitats in the northern and southern parts of the distribution are available (Crossman 1962a, Ming 1968). The habitat is characteristically small, clear, productive streams, ponds, and shallow bays of larger bodies of water, usually with mud bottoms. One exception to this involves the Ontario population in Twenty-Mile Creek (tributary to western Lake Ontario) in which substrate often consisted of gravel and flat limestone rocks (Gorrie 1975). In Oklahoma, they were sometimes found in rock or gravel pools without vegetation. In those cases, this fish was associated with a brush pile or overhanging bush. It can survive in isolated pools of seasonally temporary streams, and even when isolated in roadside ditches, providing dissolved oxygen is adequate (Ming 1968).

A detailed description of the Jones Creek habitat was provided by Crossman (1962a): water was stained brown with pH 7.65. Current speed varied from none to 0.5 feet (0.15 m) per second. Depth was 1.5-5.5 feet (0.5-1.7 m) and could fluctuate drastically, substrate was largely mud with some clay and rock. Cover consisted of extensive undercut banks and woody debris, and aquatic vegetation was diverse and often very abundant. Maximum water temperature was 84°F (29°C). Banks were variable, either marshy or consisting of shrubs or trees when the stream ran through pasture. The fish community was diverse consisting of 24 different species.

Serns and McKnight (1977) reported the habitat in Wisconsin. The water had a methyl orange alkalinity of 57.0 m/l, and a conductivity of 118 μmhos at 25.0°C. Substrate in Wisconsin habitats was characterized by Becker (1983) as sand (21%), gravel (21%), mud (17%), clay (13%), rubble (13%), silt (8%), and boulders (8%).

Habitat trends

In some of the tributaries of the Niagara River where the grass pickerel was caught close to heavily travelled roads in the early 1960s, there has been a deterioration of the habitat and vegetation. It is now found farther upstream in more typical and undisturbed habitat (E.J. Crossman, personal observations).

Yagi (2004) described the habitat and its trend in the Niagara region, as follows:

“The grass pickerel has specific habitat requirements as it is only found in wetland-associated streams with organic soils. Most of these habitats include creeks that may at sometime been channelized for agricultural drainage purposes but are normally not actively maintained and may not flow during some months but always have at minimum, permanent pool habitat.

Habitat of this nature has been lost by at least 80% in Niagara since human settlement. This type of habitat is very vulnerable to drainage activities (new drains and drain maintenance), extreme weather changes, fisheries and wetland management activities, temperature changes, channelization and fragmentation from road construction. The isolated nature of the pool habitat makes them especially vulnerable to the potential for over harvest (predation, research collections, and bait or angler harvest).

An analysis of the amount of current and historic habitat available for grass pickerel has not been done at a provincial, regional or local scale. Since this species is found only associated with organic based wetland streams, it may be possible to determine the amount of potential habitat available for each tributary. Then the amount of habitat available versus the amount occupied by this species may be used as a suitable index for trend through time monitoring purposes and a standard way to compare between tributaries and areas”.

Habitat protection

This is a poorly known, somewhat secretive, fish, which lives in areas of little interest to humans. In most areas, small maximum size and nature of the habitat renders them of little or no importance to anglers. It is, therefore, protected only by general statutes that attempt to maintain, for various human interests, the high environmental quality of such bodies of water. Many of the habitats are in agricultural situations, where siltation from breakdown of stream banks by farm animals and chemicals used as herbicides or insecticides could be harmful.

Four of the populations are in parks, which give them protection from habitat destruction: Pinery Provincial Park, Point Pelee National Park, Long Point Provincial Park and St. Lawrence Islands National Park. The population in the St. Clair delta is under jurisdiction by the Walpole Island First Nation.

In Quebec, habitat is generally protected by the "Loi sur la qualité de l'environnement" (environmental quality act). Fish habitat is also protected by the "Loi sur la conservation et la mise en valeur de la faune" (act respecting the conservation and development of wildlife) which, under articles 128.1 to 128.18, controls activities that could modify biological, physical or chemical components peculiar to fish habitat. The "Loi sur les espèces menacées ou vulnérables" (act respecting threatened or vulnerable species) makes additional provision for the protection of the habitat of threatened or vulnerable species.

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