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Species at Risk Act - Legal Listing Consultation Workbook, Grass pickerel (Quebec region)
Information on grass pickerel
Status:Species of special concern.
Last COSEWIC assessment: May 2005.
2.1. Description of the species
Grass pickerel (Esox americanus vermiculatus, Lesueur, 1846), a member of the family Esocidae, is a subspecies of redfin pickerel (Esox Americanus). Grass pickerel is small in size (less than 30 cm), but shows nevertheless the main characteristics of its family: lengthened shape, rather cylindrical body, forked tail, dorsal and anal fins far back on the body, and prominent snout well-armed with teeth. It features a green-to-brown colour with 12 to 24 irregular vertical stripes, and perpendicular black bands around the eyes.
2.2. Species distribution
In Canada, grass pickerel is found only in Quebec and Ontario, distributed in a discontinuous way, with several populations relatively concentrated in distinct areas. The Ontario distribution includes Lake Ontario and its tributaries; the St. LawrenceRiver and its tributaries (including the Upper Canada and Welland rivers); the northern shore of Lake Erie; the upstream portion of Lake St. Clair and its tributaries; the Lake Huron watershed. It is however noted that grass pickerel is absent in certain watercourses within intermediate areas that would be adequate for the species (between two places of occupation).
In Quebec, grass pickerel was observed in 3 sections of the St. Lawrence River: in Lake Saint-François, in Coteau-du-Lac (in the river section immediatelydownstream from Lake Saint-François), and in Lake Saint-Louis (Perrot island, Saint-Jean brook and Lachine). Pollution in the area of Montreal is suspected to be the cause of the absence of grass pickerel between Contrecoeur and Lachine.
2.3. Biology of grass pickerel
The nature of habitats populated by a relatively large number of grass pickerel suggests a great adaptation capability. Grass pickerel expanded beyond its initial range for three reasons: adaptability, accidental introductions and man-made introductions. As this species can support low water oxygen levels, it can survive in small water bodies having no-flow conditions in the summer and covered with ice in the winter.
2.3.2. Reproduction and spawning
Grass pickerel comes to sexual maturity at around two years of age, and would reproduce at least twice a year. The main spawning period takes place at the time of the thaw (end of March-beginning of May) in the new vegetation. The second spawning period would occur between the end of the summer and the winter. Males seem to move towards the sites favourable to spawning located upstream before females. Neither eggs nor juveniles are cared by adults. Grass pickerel is known to hybridize with redfin pickerel, chain pickerel and northern pike.
2.3.3. Movements and dispersal
Except for places suitable for egg-laying, grass pickerel is seen near shores or at the outer edge of patches of vegetation. Depending on the depthof water, there could be a vertical distribution of individuals, young ones being close to the surface and adults in deeper water. Mainly influenced by the water level fluctuations, grass pickerel aggregate in the deeper areas, even in isolated pools.
Diet varies according to growth stage. Diet is initially composed of a variety of insects and then gradually changes, integrating fish and crayfish.
In Ontario, population size varies from one placeto another depending on water conditions. Moreover, the number of individuals seems rather high considering the nature of the habitat. Elsewhere the population seems stable, while at certain places a decline is observed.
In Quebec, grass pickerel has become a rare and declining species. Samplings made from 1988 to 2003 in Lake Saint-Louis, around Perrot island, the archipelago of the îles de la Paix and Dowker island, only collected one specimen in 1988.
The typical habitat of grass pickerel is characterized by clear or slightly tinted water, rather neutral or slightly alkaline with very slow or no flow . Often shallower than 2 meters, the water body must be populated by abundant and dense vegetation. Generally, the bottom is muddy. Exceptionally, grass pickerel can inhabit water bodies with rocky bottom. It can also survive in isolated pools in sufficiently oxygenated temporary and seasonal watercourses.
Grass pickerel is very sensitive to changes in its habitat: drainage activities, sharp changes in climate and temperature, conversion of wetlandsfor recreational purposes, channelling and fragmentation caused by road construction. Grass pickerel aggregations in isolated pools are very vulnerable to overfishing (including predation, harvest for scientific purposes, bait and angler fishing).
An exhaustive inventory of the historical and current habitats of grass pickerel has not been done yet at a provincial, regional or local level. It is however possible to evaluate the potential habitat available for the species for each tributary, considering that grass pickerel is invariably associated with organic based wetland streams.
2.4. Why has COSEWIC given the grass pickerel a species of special concern status?
Here is the reason for the grass pickerel status designation by COSEWIC:
This distinct subspecies is found in 10 sites in Canada, between Lake Saint-Louis in Quebec and Lake Huron in Ontario, for a total approximate surface of 683 km². An overall decline of approximately 22% observed in the species range area is the result of habitat loss and degradation caused by human activities related to urban development (channelling and dredging).
2.5. What are the threats to the species?
2.5.1. Habitat changes and alterations
The changes to habitat caused by urban development make it less favourable for the maintenance of grass pickerel. In the areas surrounding the known populations, extirpation and clearing of watery vegetation in watercourses, related ponds or quiet bays reduced the number of favourable habitats and the possibilities of range expansion.
The greatest threats remain however the destruction and degradation of wetlands. In certain cases, an increase in the opacity of water would have a negative impact on grass pickerel feeding.
2.5.2. Agricultural activities
Watercourse silting caused by the collapse of banks due to cattle activity and the use of herbicides and insecticides could make the habitat lessfavourablefor the species.
In several areas, particularly in agricultural areas, draining works are made to remove exceeding water from the fields. Being generally open ditches, these draining works rapidly resemble to natural watercourses colonized by vegetation and fauna. The maintenance of these works is harmful for grass pickerelbecause it generally results in a decrease of water level. Where drainage works are made (digging of ditches, dredging, etc.), a decline or the extirpation of the species is noted.
An excessive decrease in water level in rearing areas could cause death of fries (1 year) and mature individuals. A similar decrease, during the winter, could result in an insufficient oxygen level in water, causing mortalities.
In Quebec, redfin pickerel is found in certain habitats close to Contrecoeur, at 57 km approximately of Lake Saint-Louis. If redfin pickerel reached this lake and was in sympatry with grass pickerel, a high rate of hybridization could be expected, and even the replacement of E. americanus vermiculatus.
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