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
Acoustic surveys are also a valuable means of mapping the lake bottom. Here again, once field
calibrations are made to ground truth the hydroacoustic data (often accomplished using
underwater video cameras), sonar scanning of the lake bottom can provide detailed information
on the relative size-distribution and composition of the substrate, and even on the density and
distribution of aquatic plants.
While a significant degree of technical expertise is required to conduct the field surveys and to
analyze the resulting data, hydroacoustics represents a highly valuable, yet cost-effective and
non-destructive tool for both fisheries surveys and habitat assessments. Because it is usually
possible to sample much more of the lake, sample the entire water column at once, and not be
confounded by issues of net selectivity and avoidance, fisheries acoustics can provide more
accurate estimates of fish abundance, density and distribution than traditional netting alone.
Furthermore, one of the real strengths of using fisheries acoustics is that it can give you a
simultaneous view of almost the entire ecosystem, from habitat (including substrate and aquatic
plants) to invertebrates to fish; in this way it can be very cost effective, as well as providing
useful information on associations among species and between species and their habitat. For
these reasons, hydroacoustic monitoring has been employed to study potential impacts of
offshore wind power projects to fish populations in marine systems (Box 1) and will no doubt
have an important role to play in baseline surveys and monitoring of effects in the Great Lakes.
Combined with more traditional supplementary field surveys, hydroacoustic monitoring could
provide much of the information on fish abundance and distribution, and on benthic habitat
conditions required for both pre-construction baseline surveys and for effects monitoring studies
at offshore wind power project sites in the Great Lakes. Prompted by the need to ensure
standardized assessment approaches, the Great Lakes Fishery Commission (GLFC) recently
funded a study group on hydroacoustics. The resulting report (Parker-Stetter et al. 2009)
summarizes standard operating procedures and recommendations for the analysis of acousticsurvey
data in the Great Lakes, and is available through the GLFC (see Appendix B). This
document, along with several related documents that have been published in the literature (i.e.
Rudstam et al. 2009) present the best available guidelines and best management practices for
Aquatic Research and Development Section 74