Growth Performance Of Hybrid Bass And Hybrid Tilapia In Conventional And Active Suspension Intensive Ponds

Abstract

Recently developed, active suspension intensive ponds are based on the idea that fish ponds (aer- ated and mixed as required for the well-being of the fish) can also serve as water purification units. The present paper compares water quality and fish growth in conventional intensive ponds (daily water exchange 500%), with active suspension intensive ponds (daily exchange 8%). The fish test- ed were hybrid tilapia (Oreochromis niloticus x O. aureus), already known to perform well in active suspension units, and hybrid bass (Morone saxatilis x M. chrysops), which is commercially cultured in conventional intensive ponds. Water quality in the two types of intensive ponds differed as a result of the “internal water purifi- cation” vs “external water purification” approach. Bacterial development was greater in the active suspension ponds. Several parameters were affected by the different rate of water exchange, including temperature and removal of ammonium. The latter was lower in active suspension ponds due to reduced washout of particles and their associated nitrifying bacteria. Nitrification was greater in tilapia active suspension ponds because of grazing by this fish. Active suspension units operated with less than 2% of the water used in the conventional intensive ponds. Hybrid bass and hybrid tilapia performed similarly well in both types of pond, indicating the economic advantage of culturing them in the water-saving active suspension system. Tilapia graze on suspended parti- cles, leading to additional savings in feed costs. The good performance of hybrid bass in active suspension ponds is herein reported for the first time. * Corresponding author. Email: anamilst@netvision.net.il 2 Email: agyoram@techunix.technion.ac.il