Offshore Wind Power Projects in the Great Lakes - Ministry of ...

Offshore wind power projects in the Great Lakes: Background and science considerations for fish and fish habitat
Interestingly, while many artificial reefs in the Great Lakes have been constructed with specific
habitat restoration or fishery enhancement goals in mind, nearshore man-made structures that
have been installed for other purposes (including water intake structures, breakwaters, jetties and
other shoreline modifications) have recently been shown to act as incidental artificial reefs in that
they can also attract significant numbers of fish species (Gannon 1990). Because they could also
serve as incidental reefs, this finding could hold relevance to turbine foundation design. There
has been a good deal of research in recent years to understand and characterize the attributes of
critical habitats for various fish species and populations in the Great Lakes. In particular, a lot of
research has been driven by ongoing efforts to re-establish spawning lake trout populations
throughout the Great Lakes. The study of spawning success and fish abundance at artificial reefs
and other man-made structures, in conjunction with assessments of natural spawning shoals, has
been integral to our current understanding of how best to implement habitat restoration for lake
trout and other fish species. The body of knowledge gained through these studies could also be
useful to guide habitat enhancement efforts at offshore wind power installations. Thus, despite
obvious differences in location, size and intended purpose, there are several aspects to reef
design that emerge from these examples which could offer insight for offshore wind proponents
interested in creating attractive fish habitat.
Enhancing structural complexity to promote fish use
Whether they are built in marine or freshwater ecosystems, it is generally the case that fish
attraction to artificial structures increases with increasing reef volume, size, surface area, and
structural complexity (Keller et al. 2006; Wills et al. 2004). Unless individual rock piles are
purposely interconnected or extended with additional material, the size of the scour protection
mounds around turbine foundations could be significantly smaller than reefs designed and built
intentionally for habitat enhancement. Regardless, there might still be options to maximize
surface area and structural complexity at these installations. For example, building up the height
of the scour protection mounds could enhance their attractiveness for certain fish species. At the
Olcott artificial reef in southwestern Lake Ontario, the presence of vertical relief and a variety of
rock sizes (including boulders greater than 1 m in diameter) were factors believed to have
attracted rock bass in a relatively short time after installation (Gannon et al. 1985). Many
artificial reefs in the Great Lakes are more than 2 m in height, which probably contributes to
their success in attracting fish by creating a visual stimulus as well as the vertical relief sought
Aquatic Research and Development Section 46