Stories From The Field

Establishing Fish Spawning Reefs in the Detroit River in Michigan

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Issue

Many fish seek out rocky areas in fast-flowing currents to deposit their eggs during spawning season. However, in the Detroit and St. Clair Rivers, many of the natural limestone reefs and rocky areas were destroyed during the construction of shipping channels. Similar spawning areas in tributary rivers were made inaccessible by dam construction, or were damaged by development and sedimentation.

Process

A diverse team of researchers has developed a process that led to new strategies for siting, designing, and constructing spawning habitat. Vessel traffic data, or Automatic Identification System (AIS) data, helped these researchers at Michigan Sea Grant better understand how commercial vessels maneuver within areas being considered for fish spawning reefs. The AIS data provide information on the type of vessel activity and related propeller wash. The goal was to understand how vessel activity affected a small test reef and predict how the vessel traffic could impact a proposed four-acre reef. The planned restoration site was in the Detroit River near the Fort Wayne historic park.

Impact

The reefs provide accessible, high-quality habitat, including rocky substrate needed to successfully incubate fish eggs. The new reefs will aid in the recovery of native fish by mimicking the lost natural limestone reefs, and may help restore populations.

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This image depicts vessel traffic data in relation to an existing test reef (red square). The green rectangle is the proposed full sized reef.

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