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
calculate or model noise transmission loss. These calculations can then be used to evaluate noise
attenuation through water and predict the area of hydroacoustic impact for different sound
sources. As an example, guidelines for underwater sound measurement techniques and methods
to calculate noise transmission loss and area of impact are provided by the California Department
of Transportation (Caltrans 2009). Finally, knowledge of the identity of fish species likely to
occupy the area (acquired through baseline fish community surveys), and of their sensitivity to
sound (which can be measured in the laboratory) will further enhance predictions of noise
impacts to fish and can guide necessary mitigation measures.
The gross behavioural response of fish communities to noise during specific construction
activities can be evaluated by comparing abundance and distribution within the anticipated area
of impact before, during and after the activity of interest. The effect of operational noise on fish
behaviour, however, will be more challenging to elucidate given the potential confounding effect
of other impacts such as EMFs or habitat creation that could also result in avoidance or
attraction. One option to evade this issue might be to conduct parallel measurements of sound
levels and fish abundance within the project area under different wind speeds (i.e. sound levels)
as well as during any periods of temporary turbine shut downs. This approach would remove at
least some of the other confounding effects, but might not permit disentangling the effects of
EMFs.
On the subject of noise monitoring, it is also important to evaluate the effectiveness of any noise
mitigation measures employed. Measurements of sound pressure levels generated by the activity
in question both with and without the selected noise attenuation measures put in place would
enable direct evaluation of whether harmful noise levels have indeed been reduced as intended.
Additionally, focused studies designed to assess the ability of different noise attenuating devices
to reduce harm or injury to fish, or to minimize behavioural disturbances would be extremely
valuable. Here again, these types of studies might involve measuring a specific response (i.e.
mortality or tissue damage in caged fish, or catch rates of fish within the impact area) both with
and without, or with varying degrees of sound attenuation employed. In this way, if it is
discovered that the mitigation measure creates no substantial reduction in sound levels or
resulting impacts to fish, improved alternatives can be developed and put in place.
Aquatic Research and Development Section 63