Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/26/2014
Publication Date: 2/19/2015
Citation: Green, B.W. 2015. Winter performance of an outdoor biofloc production system for channel catfish [abstract]. Aquaculture America Conference. p. 191.
Technical Abstract: In the tropics, outdoor biofloc technology production systems are operated year-round. While channel catfish (Ictalurus punctatus) have been grown successfully in an outdoor biofloc production system, these studies were conducted only during the growing season and production tanks were idled for the winter after harvest. If an outdoor BFT production system is to be viable at temperate latitudes, then data gaps related to system and fish performance over the winter must be addressed. The present study was conducted to address some of these data gaps. Waters from a recently completed biofloc production experiment that contained low (153.3 mg/L) and high (606.7 mg/L) total suspended solids were retained for this study. Three 15.7-m3 tanks per water type each were stocked (8 kg/m3) with market size channel catfish retained for a 152-d study from November to April. Catfish survival through the winter was high (99.75%) in biofloc tanks and did not differ significantly between treatments. Net fish yield did not differ significantly between treatments. However, net fish yields were 1-4% less than initial fish biomasses. Mean chlorophyll a concentrations were similar in both treatments during the first 55 days, after which treatments diverged and chlorophyll a concentration increased linearly (P < 0.001, R2 = 0.721) to a mean final concentration of 2,251.7 mg/m3 in the low solids treatment. Ammonia from ammonium chloride spikes (1.25-1.5 mg NH4-N/L) added on three occasions during the experiment was biotransformed completely putatively by algal uptake and nitrification. Ammonia biotrnsformation rate was linearly related (P = 0.006, R2 = 0.920) to mean water temperature in the high solids treatment, whereas a semi-logarithmic relationship was observed in the low solids treatment (P < 0.001, R2 = 0.878). Water in the biofloc production tanks appeared to retain through the winter the ability to biotransform ammonia regardless of whether phytoplankton or suspended solids predominate, which may allow high feeding rates to be attained earlier the following spring.