Integrated culture of Eucheuma denticulatum, Perna viridis, and Crassostrea sp. in Carcar Bay, Cebu, Philippines

Abstract

The three high-value extractive species, Eucheuma denticulatum, Perna viridis and Crassotrea Eucheuma denticulatum, Perna viridis and Crassotrea sp, have been integrated into the existing commercial finfish culture of Chanos chanos and Trachinotus blochii in the Carcar Bay, Eastern Cebu, Philippines, following the Integrated Multitrophic Aquaculture (IMTA) concept. Two sampling sites (573 m apart) were selected; the experimental site, and control site. Biomass and growth rates of all three extractive species were measured monthly, along with physico-chemical parameters in the two sites, monitored for a period of up to one year for E. denticulatum and seven-month for P. viridis and Crassostrea sp. Results showed that both seaweed and P. viridis adopted in the fish farming site, where water temperature, salinity, pH, dissolved oxygen were found to be well within the optimal range of the three species. Growth of each species, however, aside from the seasonal changes in the weather pattern that influenced water movement, was mainly affected by the presence of epiphytes, predators and fouling organisms that were present during culture. These factors have reduced their potential biomass and growth rates. The introduction of the extractive species in the fish farm appeared to have checked the adverse effects of fish culture activities whose daily inputs of commercial feeds, could led to the suspended solids. The levels of ammonia at 0.5 m (average: 0.05 mg/L) in the experimental site was observed to be lower than that of the control site, whereas the levels of nitrate (ave: 0.23 mg/L) and phosphate (ave: 0.15 mg/L) in the same depth remained relatively high suggesting that these nutrients were not absorbed much by E. denticulatum. The use of IMTA concept, which is found to work well in the culture of milkfish/pompano with the integration of locally-available extractive species, should be promoted and expanded in the Philippines.