Lake Substrate Critical Component of Fish Habitat
Posted on: February 16, 2017
Thunder Bay Substrate Mapping
Twenty-six square kilometers of lake bottom within Thunder Bay were mapped for substrate type by Environment and Climate Change Canada in 2012. Substrate, or bottom type, is a critical component of fish habitat, also influencing spawning activity.

Fish and wildlife habitat was the central topic of discussion at a February 8th meeting of the Public Advisory Committee to the Thunder Bay Remedial Action Plan, or harbour cleanup plan.

Thunder Bay fish and wildlife habitat has been degraded by urban and industrial waterfront development. Lake Superior lake bottom and shoreline habitat, as well as habitat along rivers and streams flowing to Superior, has been lost as a result. Remedial Action Plan habitat restoration projects have assisted in restoring spawning areas and wetland conditions in several harbour locations with the goal of creating productive conditions nurturing fish and aquatic life as well as bird and animal populations. Despite these efforts there is still room for habitat enhancement balancing harbour environmental and economic considerations.

Lake bottom substrate, or bottom type, is a critical component of fish habitat, also influencing spawning activity. At the February 8th meeting, Rick Kiriluk of Environment and Climate Change Canada (ECCC), outlined work to quantify the various types of lake bottom material in Thunder Bay on Lake Superior.

Rick began his presentation by stating that the type of lake bottom material, be it sand, fine silt, gravel, cobble, or other material, is directly related to the quality of fish habitat. He said that data collected during the substrate survey would be developed into a habitat classification incorporating information about the quality of fish habitat, suitability for various species, etc.

Rick said that while he was presenting information about substrate mapping in Thunder Bay on behalf of ECCC, it was actually Hans Biberhofer, also of ECCC, who had carried out the work. He said that Hans had carried out such work in all of the Great Lakes, over many years.

Survey work was completed in three areas – Thunder Bay Harbour proper, within the breakwall; Thunder Bay west shore, from approximately Chippewa to Sturgeon Bay, in about a 2 km. wide strip out from the shore; also Welcome Islands, taking in an area around the entire island group and stretching out approximately 500 m. from the shore of the islands.

Data collection included both soundings, to get an accurate picture of bathymetry, or depths and bottom contour, as well as underwater video at a sub-set of sites. Soundings were run in a series of “lines.” Underwater video was utilized to obtain an accurate identification of bottom type. Using the Welcome Islands as an example, the following activities were used in the data collection process:

  • 84.2 km. of sounding lines
  • 192,804 soundings
  • 28 underwater video sites.

Data collection resulted in quantification of Thunder Bay bottom type over about 26 square kilometers. Rick cautioned that while video classification of bottom type was very accurate at specific video sites, conditions across  broader areas were extrapolated. The area surrounding the Welcome Islands, for example, was determined to have a preponderance of sand (well defined sand waves), followed by fine grained material and also substantial amounts of cobble. All of this data is valuable as it relates to habitat for various fish species. Rick concluded by saying that collected data would be compiled into a substrate classification for Thunder Bay.

Rick was asked several questions at the meeting, those questions to which he did not have an immediate reponse are answered below:

1)      Why the absence of data for the North Harbour Contamination area?

This area was not included in the workplan as this area is contaminated with mercury which has greatly compromised the fish habitat quality. Substrates in that area have been characterized in other studies/reports (R.F. Foster Dec 2012 – Thunder Bay North Harbour Fish Community and Habitat Synthesis).

 2)      Why the absence of data in nearshore areas, specifically boat ships, channels and basins?

This information was not included in the workplan as these areas were considered to be highly degraded fish habitat due to dredging, infilling, shoreline hardening. The objective of the project was to assess the quantity of fish habitat (through substrate classification and subsequent habitat classification) that is more closely linked or typical of a lesser degraded condition and more conducive to supporting healthy fish populations.

 3)      There was mention of substrate mapping in the St Marys River.

The work in that area was specific to contaminated sediments.  The loss of fish habitat BUI in the St Marys AOC is mainly loss of rapids and wetland habitat. The substrate/habitat classification approach would not be applicable.

 The February 8th meeting was attended by about 25 people, including several members of the Thunder Bay Field Naturalists (TBFN), as well as a representative of the Nature Conservancy of Canada (NCC). In addition to fish habitat, meeting participants discussed ideas such as rehabilitation of wetlands along Thunder Bay’s harbour shore. Some areas have been damaged by industrial activity, including encroachment by debris and sawdust, or even infilled to gain additional industrial property. The Public Advisory Committee is working to formulate next steps to improve harbour habitat. Input from members of the TBFN and the NCC representative was highly appreciated by Public Advisory Committee members.


Presentation by Rick Kiriluk of Environment and Climate Change Canada

Photos of substrate mapping work being carried out in Thunder Bay by Hans Biberhofer and crew.



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