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
on fish could be confounded by other effects from operating wind turbines, such as noise and
EMFs which could result in avoidance. These potential confounding effects on fish behaviour
might not easily be controlled, but should certainly be considered in the context of assessing the
artificial reef effect of turbine structures.
A number of studies have been conducted to evaluate the effectiveness of artificial reefs as fish-
concentrating devices, both in marine systems as well as within the Great Lakes. The foundations
and scour protecting material around turbine structures could act as fish aggregating devices as
well, meaning that the methods employed in artificial reef monitoring studies could also be
applied at offshore wind power projects. Fortunately, it has been demonstrated that fish
aggregations tend to be localized near introduced hard structures. As a result, surveys to assess
fish use or attraction to artificial structures can be targeted within and around them, reducing the
spatial extent of sampling efforts required for reef monitoring studies. Consequently, visual
techniques can be a feasible means of quantifying fish stocks near artificial reefs and have been
used in many of the attempts to do so. For example, as part of a study to determine the sport fish
attraction potential of two artificial reefs in Lake Erie, both stationary, and mobile underwater
video surveys conducted by divers were used to identify and enumerate fish on a monthly basis
at artificial reef sites and adjacent non-reef control sites (Kelch et al. 1999). Observations by
scuba divers swimming along transects were similarly used to estimate the number and species
of fish at artificial reef and reference sites (Kevern et al. 1985) as well as before and after reef
construction (Creque et al. 2006) in monitoring studies of two different artificial reef projects in
Lake Michigan. In order to investigate the potential for wind turbines to function as artificial
reefs and fish aggregation devices, estimation of fish abundance and diversity at varying
distances from turbines within two offshore wind power project areas in Sweden were also
conducted by means of visual scuba census (Wilhelmsson et al. 2006) which was subsequently
repeated several years later at one of those sites (Andersson & Ohman 2010).
While visual surveys can be very useful in this context, their major downfall is that they can only
be conducted during the day and in water shallow or clear enough to enable the diver or camera
to visualize the surrounding area. Recognizing these limitations, several artificial reef studies in
the Great Lakes have combined daytime visual surveys with gill net sampling, where nets were
set overnight or over a 24-hour period in order to ensure representative sampling of both diurnal
Aquatic Research and Development Section 68