Spawning by native fish species at two constructed spawning grounds in the Detroit River

Over the last century, much of the spawning and nursery habitat for native fishes in the Detroit River was destroyed by construction of shipping channels, filling of coastal wetlands, and contamination from industry and combined sewer overflows.  This resulted in dramatic declines in abundance of many fish species, but most significantly for lake whitefish and lake sturgeon.  Since 2004, construction of two spawning reefs in the Detroit River showed that fish populations can be remediated and produce higher numbers of native fish species. Prior to construction, these two areas were little used by spawning fish.  In the first two years following spawning habitat construction, the first constructed habitat was utilized by large numbers of fish for reproduction, including 14 native fish species. Following construction of the second spawning reef, more than 10 species of fish spawned, including for the first time, lake sturgeon.  Egg mat and larval fish sampling conducted at and just downstream of the spawning reefs showed an increase in egg deposition and egg survival through hatch.  The rapid rate with which fish utilized the new habitats supported the hypothesis that populations of desirable fish species in this river were limited by available spawning habitat.