Aquaculture Crsp 22nd Annual Technical Report

An experiment was conducted in nine 200-m2 earthen ponds at the Asian Institute of Technology (AIT), Thailand from 17 July 2003 to 3 March 2004 (230 days). The objectives of the study were to assess the feasibility of co-culture of lotus and hybrid catfish in intensively fed ponds, to assess nutrient recovery from feed waste by lotus plants, to assess pond mud characteristics after lotus-fish co-culture, and to compare catfish growth with and without lotus integration. There were three treatments in triplicate: (1) catfish at 25 fish m-2; (2) lotus at 50 seedlings pond-1; and (3) lotus-catfish co-culture (lotus 50 seedlings pond-1 and catfish at 25 fish m-2). Lotus plants, root intact, were transplanted to ponds of treatments with lotus at a density 50 plants pond-1. Hybrid catfish were stocked at a density 25 fish m-2 in treatments with catfish. Experimental catfish were fed with commercial floating pelleted feed. Feeding rate was adjusted for each pond separately based on the monthly fish growth measurement and estimated average catfish survival. There were no nutrient inputs in lotus ponds. Catfish growth performance was not significantly different (P > 0.05) between catfish and co-culture treatments. However, catfish survival was unpredictably low. There were no significant differences in lotus growth performance between lotus and co-culture treatments; however, total harvested lotus biomass was lower in comparison with previous production records in similar ponds. Lotus co-culture with catfish or lotus culture in ponds resulted in reduced pond mud nutrient concentrations. Nutrient loss from mud in a 1-ha pond was 0.32 tonnes N, and 0.44 tonnes P, out of which 44 kg N and 9.3 kg P were incorporated into the harvested lotus biomass. Most of the water quality parameters remained in the safe range for catfish growth and thus, integration of lotus and catfish could be a potential strategy to recover nutrient from intensive catfish feeding systems.