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Historic and comparative perspectives on rehabilitation of marshes as habitat for fish in the lower Great Lakes basin

1996; Canadian Science Publishing; Volume: 53; Issue: S1 Linguagem: Francês

10.1139/f96-020

1205-7533

Thomas H. Whillans,

Flood Risk Assessment and Management

Retrospective and comparative assessments of fish habitat have been used to guide rehabilitation in Cootes Paradise, a marsh at Hamilton, Ont., on Lake Ontario. The marsh was severely altered by human and natural stresses, including high water levels, influx of fine eroded sediments, and channelization. Recovery has been limited by a different but overlapping set of stresses, including the continued influx of fine eroded sediments, resuspension of sediments, exotic fish, and increased fetch. Assessment has involved the use of accumulator-, residue-, and replica-type retrospective evidence and the comparison of Cootes Paradise with other reference marshes. The emergent narrative science (a synthesis of science in historical and environmental context that serves as a partially testable hypothesis), verified and adjusted by small scale experiments, has identified the need to re-introduce vegetation, reduce fetch, exclude common carp (Cyprinus carpio), anchor the marsh sediments, and reduce the influx of land use derived fine sediments. Narrative science uses the memory of the marsh for historical information on ecological degradation and in the form of the remnant natural resilience upon which ecological rehabilitation could build. The narrative science provides the basis for adaptive management and the monitoring that it requires. Resume : Des evaluations retrospectives et comparatives de l'habitat du poisson ont servi a guider les travaux de restauration du marais Cootes Paradise a Hamilton, sur le lac Ontario. Le marais avait ete gravement perturbe par des agressions humaines et naturelles, notamment le haut niveau de l'eau, l'apport de sediments d'erosion fins et le creusement de chenaux. Le retablissement a ete limite par une serie differente mais simultanee d'agressions, notamment la poursuite de l'apport de sediments d'erosion fins, la remise en suspension des sediments, la presence d'especes exotiques et l'augmentation du fetch. Nous avons eu recours pour l'evaluation a des justifications retrospectives de type accumulateur, residu et replique, et a la comparaison de Cootes Paradise a d'autres marais de reference. Grâce a la nouvelle approche narrative (synthese de la recherche, inscrite dans son contexte historique et ecologique, qui sert d'hypothese partiellement verifiable), apres verification et ajustement par des experiences a petite echelle, nous avons releve la necessite de reintroduire de la vegetation, de reduire le fetch, d'eliminer la carpe ( Cyprinus carpio), d'ancrer les sediments du marais et de reduire l'apport de sediments terrigenes fins. L'approche narrative utilise la memoire du marais pour obtenir des donnees historiques sur la degradation ecologique et pour mesurer la resilience naturelle residuelle sur laquelle pourra s'appuyer le retablissement ecologique. Cette approche scientifique donne une base pour une gestion adaptative et pour la surveillance que cette gestion necessite. (Traduit par la Redaction)