WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2015 57 crude protein of 36, 32 and 28 percent and different particle sizes (3, 4, 6 and 10 mm). As before, the protein content decreased and the particle size increased as the fish grew. The daily feeding rate during the grow-out phase ranged from 3 to 1 percent of fish body weight. Fish were sampled every 30 days with 10 percent of fish captured from each cage to evaluate growth and adjust the feeding rate (Fig. 4). Water temperature, dissolved oxygen, pH and conductivity were monitored daily. The performance parameters evaluated were final weight, weight gain (final weight – initial weight), feed conversion ratio (feed consumption/ gain weight), condition factor, survival rate and production rate (kg/m3). Water temperature ranged from 25.5 to 32.2 C with mean of 29.1 ± 1.4 C. Dissolved oxygen ranged from 6.1 to 10.3 mg/L with a mean of 8.3 ± 0.8 mg/L. The pH ranged from 4.0 to 8.8 with a mean of 6.5 ± 1.1 and conductivity ranged from 442 to 700 µS/cm with a mean of 606 ± 70 µS/cm. Environmental parameters of the water fluctuated within the acceptable range for the rearing of tambaqui (Aride et al. 2007). The pH of the lake ranged widely from 4.0 to 8.8. The lake was limed only once during the study. The pH declined gradually during the study, explained by a rainwater pH of around 5.5. Rainfall in the study region is divided clearly between a rainy winter season from April to July and a dry summer season from October to January. The lake is supplied by only rainwater that is collected by the small basin around the lake. Tambaqui has relatively good tolerance to acidic environments with adaptive strategies involving haematological adjustments, ion regulation and mucus production (Aride et al. 2007). The resistance of tambaqui to acidic water reflects its occurrence in naturally acidic environments in waters of the Amazon Basin (Silva et al. 2008). In the nursery phase, the greatest final weight (83.5 ± 18.0 g) was obtained at 50 fingerlings/m3. Survival over 97 percent was observed in the nursery phase, similar to that obtained by Silva et al. (2007). The best feed conversion ratio (0.8) in the nursery phase was obtained at a density of 300 fingerlings/m3 but the feed conversion ratio of all density treatments was similar (0.8-1.1). The final biomass density of 14.0 kg/m3 was significantly greater for fish at 300 fingerlings/m3. The recommended density in nurseries for producing juveniles tambaqui reared in small-volume cages is 300 fish/m3. In the nursery and grow-out phase, stocking density had a significant effect on production, with the greatest production in cages stocked at the highest density. Weight gain and specific growth were inversely proportional to density. Feed conversion and condition factor were not influenced by the evaluated densities. In the growth phase, the greatest final weight (1.03 kg) was obtained at 20 fish/m3 (Fig. 5). The feed conversion ratio ranged from 2.1 to 2.4 and there were no significant differences among densities. Production rate was significantly affected by stocking density, reaching 48.7 kg/ m3 at the highest density of 60 fish/m3. Similar result of 45.8 kg/m3 was obtained at 60 juveniles/m3 in a floodplain in central Amazonia (Gomes et al . 2006 ).The total survival rate (100 percent) in the grow-out phase confirms that tambaqui clearly adapt to cage culture. The density of 20 fish/m3 is the best to grow tambaqui in cages to a market size of ~1 kg. In the local northeast market, consumers prefer to buy fresh whole tambaqui with a weight of ~1 kg. The results show that tambaqui cage culture is viable in lakes supplied by rainwater and can be integrated with multiple-use water bodies. Additionally cage systems reduce or eliminate bird predation and facilitate feeding, grading and harvesting of fish. Further research is needed to improve growth to marketsize and decrease feed conversion rates to reduce production costs. Notes Carlos Alberto Da Silva, Embrapa Coastal Tablelands, Av. Beira Mar, 3.250, CEP: 49.025-040 Aracaju, Sergipe-Brazil, carlosalberto.silva@embrapa.br References Aride, P.H.R., R. Roubach and A.L. Val. 2007. Tolerance response of tambaqui Colossoma macropomum (Cuvier) to water pH. Aquaculture Research 38:588-594. Gomes, L.C., E.D. Chagas, H. Martins-Junior, R. Roubach, E.A. Ono and J.N.P. Lourenço. 2006. Cage culture of tambaqui (Colossoma macropomum) in a central Amazon floodplain lake. Aquaculture 253:374-384. MPA (Ministério da Pesca e Aquicultura do Brasil). 2011. www. mpa.gov.br/files/docs/Boletim_MPA_2011_pub.pdf Santos, E.F., M.M. Tavares-Dias, D.A. Pinheiro, L.R. Neves, R.G.B. Marinho and M.K.R. Dias. 2013. Fauna parasitária de tambaqui Colossoma macropomum (Characidae) cultivado em tanquerede no estado do Amapá, Amazônia oriental. Acta Amazônica 43:105-112. Silva, C.R., L.C. Gomes and F.R. Brandão. 2007. Effect of feeding rate and frequency on tambaqui (Colossoma macropomum) growth, production and feeding costs during the first growth phase in cages. Aquaculture 264:135-139. Silva, A.E.P., C.F. Angelis, L.A.T. Machado and A.V. Waichaman. 2008. Influência da precipitação na qualidade da água do Rio Purus. Acta Amazônica 38:733-742. FIGURE 4. Tambaqui fingerlings after 30 days of culture. FIGURE 5. A tambaqui of market size (~1 kg). FIGURE 5. A tambaqui of market size (~1 kg).
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