Analysing the impact of freshwater aquaculture on wild fish populations using dual frequency identification sonar (DIDSON) technology / E.C. Enders ... [et al.]. : Fs97-6/3192E-PDF

“Dual-frequency identification sonar (DIDSON) technology has been used for a wide range of fisheries applications. The DIDSON offers important advantages over other sampling techniques since surveys are non-invasive and do not require capturing, handling or disturbing fish or their environments. Consequently, DIDSON technology is well-suited for use in an aquaculture setting. DIDSON images are constructed from sound compared to light, allowing for DIDSON sampling 24 h a day and in all turbidity conditions. Using the DIDSON, we collected data on wild fish distribution and abundance before and after the development of a new aquaculture site at impact and control sites in Lake Diefenbaker, Saskatchewan. A standardized field protocol was established to improve the environmental monitoring design for DIDSON field studies on wild fish in pelagic environments. DIDSON recordings were standardised to detection-per-unit-effort (DPUE in number of fish ·10 m-3·2 h-1) in four depth strata for the three different study sites. DPUE at the Kadla cages were greatest during the early morning feeding period when large schools of fish (50 fish) were detected. In addition, gillnets were set to allow ground-truthing of the DIDSON footage. Six fish species (Cisco (Coregonus artedi), Walleye (Sander vitreus), Lake Whitefish (Coregonus clupeaformis), Yellow Perch (Perca flavescens), Goldeye (Hiodon alosoides), and Rainbow Trout (Oncorhynchus mykiss)) were caught during gillnetting with higher catch rates in the vicinity of the cages compared to the control site. DIDSON technology is valuable to assess the behaviour of wild fish surrounding aquaculture infrastructures"--Abstract, p. vii.

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