FEED UTILIZATION BY LARGEMOUTH BASS Micropterus salmoides AND BLUEGILL Lepomis macrochirus AT THREE TEMPERATURES SUITABLE FOR PRODUCTION OF LEAFY GREENS IN AQUAPONIC SYSTEMS
A quaponic (AP) farmers in temperate regions must utilize a greenhouse or insulated buildings to produce year-round . I n cold weather, heating water is not economically viable for tilapia production (28°-30°C) in AP, particularly when optimal temperatures for growth of leafy greens is 16°-24° C. Native fish species may provide producers with an alternative. While temperature ranges for optimal growth are known for many native Kentucky fish , little research has been conducted on feed utilization at lower temperatures. This study evaluates Largemouth bass (LMB; Micropterus salmoides) and bluegill (BG; Lepomis macrochirus ) feed utilization at three temperatures suitable for production of leafy greens in AP.
Figure 2. Projected TAN production per day for Largemouth bass (LMB), bluegill (BG), and tilapia.
Figure 1. Feed consumption/day (g) for Largemouth bass (LMB) and bluegill (BG) at three temperatures.
A 10-week feeding trial was conducted in three separate RAS containing six 0.42m 3 fish tanks. Each system was kept at one of three temperatures (26°, 22°, and 18°C ) suitable for growth of leafy greens in AP . LMB and BG were stocked into separate tanks at 15 fish/tank, with an initial stocking density of 107 and 91.7 g/m3 , respectively. Fish were fed 40% protein floating feed to satiation 1x/d. Total feed consumption (g) was recorded. TAN, NO2 , NO3 and alkalinity were tested 1x/wk . Temperature, pH, and DO were recorded daily. TAN production/day was estimated based on feed consumption per tank using the formula TAN = feed input (g) x % protein of feed x 0.092/time.
LMB consumed significantly (P ≤ 0.05) more feed than BG at all temperatures evaluated (Fig 1) . However, LMB consumed significantly (P≤ 0.05) less feed as temperatures decreased . F eed consumption by BG was not significantly (P>0.05) impacted by temperature . Projected TAN was highest for LMB at 26ᵒC (Fig 2) , higher than BG, but still half of what is projected for tilapia at 26ᵒ C fed a diet containing 32% protein. In order to match levels of TAN produced by tilapia at 26ᵒC, 1.9m3 and 4m3 of fish production would be required for LMB and BG, respectively.
