Using active acoustics to assess habitat restoration in a freshwater lake.

Abstract

Artificial structures increase bottom complexity in man-made reservoirs and aim to increase fishery production by providing improved refuge, forage, and reproduction habitat. Electrofishing is typically employed to assess the effectiveness of these structures but is limited to shallow water sites. Active acoustic technology is a non-invasive sampling method that is more flexible than electrofishing, as it is operational in both deep and shallow water sites. Active acoustics also provides a continuous data series at one location to obtain high-temporal resolution information. An acoustic water column profiler was deployed for 1 week at each of two sites: (1) a control site with no introduced structure and (2) a treatment site with artificial refuge habitat. Difference in fish abundance, vertical distribution, and diurnal behavior between the two sites was assessed from the volume backscatter time series. Variation in fish activity between the two sites was compared. This work demonstrates the utility of active acoustics in assessing the effectiveness of freshwater habitat alteration beyond the scope of conventional techniques. A more comprehensive evaluation of habitat restoration is crucial in guiding the development of future conservation efforts.