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 milkfi sh, Chanos chanos, under monoculture and biculture conditions in aquaria an d ponds were studied from May 1997 to March 1998. Water quality of both sys tems was monitored. The two species have reciprocal characteristics in thei r biological requirements and byproducts. Both species attained higher grow th rate in biculture: in aquaria Gracilariopsis obtained a mean daily growt h 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, Gracilariops is obtained a mean daily growth rate of 3.68 +/- 0.39% in biculture and 2.4 6 +/- 0.38% in Gracilariopsis monoculture while Chanos had a mean daily gro wth rate of 4.81 +/- 0.33% in biculture and 2.9 +/- 0.1% in Chanos monocult ure. The growth rates for both Gracilariopsis and Chanos decreased weekly t hrough one month of culture. Higher dissolved oxygen levels were observed i n Gracilariopsis monoculture and in biculture and significantly lower in Ch anos monoculture. Chanos did not control epiphytism in Gracilariopsis. Ther e 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.