Great Basin Naturalist


Two recirculating aquaculture systems were constructed using a sequence of five tanks each. Each system contained two plant species, duckweed (Lemna minor) and Chinese water chestnut (Eleocharis dulcis); two fish species, channel catfish (Ictalurus punctatus) and tilapia (Tilapia aurea); and a freshwater prawn (Macrobrachium rosenbergii). Duckweed production during the 132-day experiment reached as high as 87.2 tons/hectare/year (t/ha/yr). Water chestnut production was not successful in the restricted light situation of the lab, but in an outdoor test planting, corn production was 37.2 t/ha/yr. Four feeding trials were attempted using the following percent of fish body weight: 2.5% commercial feed; 5% wet duckweed; 15% wet duckweed; and 15% wet duckweed with 1% commercial feed. Feed to flesh conversion ratios averaged 1.97:1 for the three control tanks and 1.44:1 overall for the treatment tank. The fish-fed duckweed and commercial feed grew as well or better than those fed commercial food alone.