Aquatic habitat manipulation research at Turkey Lakes watershed

Objective

Determine the effect of the removal of nearshore cover and the alteration of bottom substrate on fish communities and the productive capacity of aquatic ecosystems

Pretreatment Site Selection

In a study designed to last 4 to 5 years, three experimental lakes were selected according to the following criteria (Figure 1):

  • Lake must have a well-established fish community with a minimum of one predator and one prey species;
  • Lake must have no existing shoreline development;
  • Lake must be closed to fishing year round; and
  • Permission must be obtained from stakeholders and landowners prior to habitat manipulation.

Figure 1: Map of Turkey Lakes Watershed showing selected lakes.

Figure 1: Map of Turkey Lakes Watershed showing selected lakes.

Treatment in Selected Lakes

In order to mimic human encroachment into aquatic ecosystems (e.g. changes to the littoral zone associated with cottage development), habitat diversity was decreased in Quinn Lake (Figure 2), and in Little Turkey Lake in 1999 (Figure 3). Habitat manipulation in Wishart, the third experimental lake, will replicate Quinn in 2000. Batchawana Lake remains unperturbed as a control lake.

Picture of Figure 2: Quinn Lake - 1999 Removal of all nearshore coarse woody debris (<2m depth) from 50% of the shoreline.

Figure 2: Quinn Lake - 1999 Removal of all nearshore coarse woody debris (<2m depth) from 50% of the shoreline.

Picture of Figure 3: Little Turkey Lake - 1999 Water/gas permeable geotextile covering the nearshore bottom substrate of a portion of shoreline where woody debris was removed (same wood removal treatment as Quinn Lake). The geotextile simulates uniformity associated with beach sand.

Figure 3: Long Description

Little Turkey Lake - 1999 Water/gas permeable geotextile covering the nearshore bottom substrate of a portion of shoreline where woody debris was removed (same wood removal treatment as Quinn Lake). The geotextile simulates uniformity associated with beach sand.

Ongoing Monitoring Program (led by DFO-GLLFAS, SSM unless otherwise indicated)

Characteristics of Resident Populations

  • Fish abundance, biomass, production, and community dynamics (Figure 4)
  • Abundance and diversity estimates for zooplankton, phytoplankton, and bottom-dwelling organisms
  • Determination of changes in food web structure using stable isotope analysis (M. Whittle, DFO-GLLFAS, Burlington)
  • Assessment of fish distribution in relation to habitat type using underwater video camera, transect swims, and location-specific catch data
  • Determination of species, age, volume, and surface area of woody debris (Partner: Dr. W. Cole, OFRI). Subsampling of wood to determine biofilm-Chlorophyll-a content and invertebrate diversity and density

Picture of Figure 4: Fish measured, weighed, marked, and scales are removed for determination of age, growth, biomass and production.

Figure 4: Fish measured, weighed, marked, and scales are removed for determination of age, growth, biomass and production.

Physical and Chemical Characteristics of Lakes

  • Measurements of dissolved oxygen, temperature, pH, alkalinity, conductivity,nutrients, major ions, metals, turbidity, and sedimentation rates to determine changes associated with the manipulation (Dr. D. Jeffries, Environment Canada)
  • Continual monitoring of water levels
  • Pre-manipulation mapping of all in-water habitat including macrophytes, sediment characteristics, woody debris, and overhanging vegetation
  • Post-manipulation assessment of wood redistribution into cleared areas
  • Subsample of trees marked and tree mortality by species and age-class monitored for long-term determination of a) natural mortality rates of trees in the forest-lake ecotone, and b) natural log input rates into lakes (Dr. W. Cole, OFRI)

Implications

Provides scientific basis for policy and guidelines relating to nearshore fish
h abitat and forest-lake buffer zones as required by the Department of Fisheries and Oceans and the Ministry of Natural Resources.

This project is supported by the Environmental Science Strategic Research Fund. Thanks to the Turkey Lakes Steering Committee for their assistance. Thanks also to the numerous employees, interns, and students who have contributed to the collection of field data.

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