Comparison of the performance of the agarophyte, Gracilariopsis bailinae, and the milkfish, Chanos chanos, in mono- and biculture

The performances of the agarophyte, Gracilariopsis bailinae, and the milkfish, Chanos chanos, under monoculture and biculture conditions in aquaria and ponds were studied from May 1997 to March 1998. Water quality of both systems was monitored. The two species have reciprocal characteristics in their biological requirements and by-products. Both species attained higher growth rate in biculture: in aquaria Gracilariopsis obtained a mean daily growth rate of 4.72 ± 1.64% for biculture and 3.44 ± 2.74% in Gracilariopsis monoculture while Chanos had a mean daily growth rate of 4.81 ± 2.13% in biculture and 4.13 ± 2.13% in Chanos monoculture. In ponds, Gracilariopsis obtained a mean daily growth rate of 3.68 ± 0.39% in biculture and 2.46 ± 0.38% in Gracilariopsis monoculture while Chanos had a mean daily growth rate of 4.81 ± 0.33% in biculture and 2.9 ± 0.1% in Chanos monoculture. The growth rates for both Gracilariopsis and Chanos decreased weekly through one month of culture. Higher dissolved oxygen levels were observed in Gracilariopsis monoculture and in biculture and significantly lower in Chanos monoculture. Chanos did not control epiphytism in Gracilariopsis. There was no difference in epiphytism in either culture systems in aquaria, but a significant growth of green algae occurred in ponds with monoculture of Gracilariopsis.