Assessing the interactions between wild fish populations and freshwater cage aquaculture
Interactions between freshwater aquaculture and wild fish populations are an important consideration for aquaculture managers and the sustainable management of the freshwater aquaculture industry. Freshwater aquaculture activities can affect wild fish communities because of physical changes in the habitat, increased noise associated with aquaculture activities, release of farm wastes, and escaped cultured fish. The presence of cage farms may impact the distribution of wild fish communities, trophic relationships, and the abundance of wild fish species. The physical structures of the cages and the farming activities had been shown to attract wild fish, but the extent of this attraction had not been well characterized. This project conducted a quantitative survey, using Dual frequency IDentification SONar (DIDSON) technology, in Lake Diefenbaker, Saskatchewan, to assess both pre- and post-operational interactions, specifically related to differences in fish abundance in the vicinity of the cage farms, to determine whether fish farms attract wild fish species, particularly during feeding. This information supports the assessment of potential impacts of cage farms on wild fish populations and contributes to the development of regulatory standards and assessment methods.
DIDSON footage was collected before (2011-2013) and after (2014-2015) the installation of net cages at a new aquaculture site in Kadla Coulee and at a reference site without cages in Lake Diefenbaker. The efficacy of the DIDSON to detect changes in wild fish habitat use around fish farms was assessed. DIDSON technology is non-destructive towards fish habitat and allows for the non-intrusive detection of fish during both day and night, regardless of the turbidity. DIDSON recordings were standardized 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 fish farm cages were greatest during the early morning feeding period when large schools of wild fish (50 fish) were detected. Gill nets were set to obtain indications of possible wild fish species seen 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. An operational protocol and data analysis procedure for the niche- application of DIDSON within an aquaculture setting was established and advice was provided for future DIDSON surveys. In conclusion, this research narrowed the knowledge gap on the environmental interactions between cultured and wild fishes to make informed management decision in the future.
Enders, E.C., V.M. Danco, C. Podemski, and C. Wlasichuk. 2017. Analysing the impact of freshwater aquaculture on wild fish populations using Dual Frequency Identification Sonar (DIDSON) technology. Canadian Technical Report of Fisheries and Aquatic Sciences. 3192:50.
2015 - 2016
Research Scientist, Environmental Science Division, Freshwater Institute
501 University Crescent, Winnipeg, Manitoba
Wild West Steelhead Ltd., Saskatchewan
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