Ugo Lima Silva

Cultivo da tilápia do Nilo Oreochromis niloticus em sistema de bioflocos com diferentes densidades de estocagem

Objetivou-se com este trabalho avaliar a qualidade da agua e o desempenho zootecnico da tilapia do Nilo (Oreochromis niloticus) cultivada em sistema de bioflocos sob diferentes densidades de estocagem. O experimento foi conduzido na Estacao de Aquicultura da Universidade Federal Rural de Pernambuco, Brasil, durante 128 dias. Peixes de 123,0±0,6g foram estocados em 12 tanques circulares (800 L) em um delineamento inteiramente casualizado com tres tratamentos (D15, D30 e D45, correspondendo as densidades de 15, 30 e 45 peixes.m-3) e quatro repeticoes. Entre as variaveis de qualidade de agua, o oxigenio dissolvido teve efeito significativo (P≤0,05) entre as densidades, com a menor concentracao (3,97 mg O2.L-1) na maior densidade testada (45 peixes.m-3). A amonia total apresentou diferenca estatistica (P≤0,05) entre o tratamento D15 e os demais; e o nitrito, entre a densidade de 15 e 45 peixes.m-3, porem ambos numa relacao diretamente proporcional com o aumento da densidade de estocagem, apresentando maiores concentracoes medias de 2,56 e 3,26 mg.L-1 de amonia e nitrito, respectivamente, na densidade de 45 peixes.m-3. O desempenho zootecnico, no tratamento D45 apresentou melhor resultado, com produtividade de 16,6 Kg.m-3, com diferenca significativa entre os tratamentos (P≤0,05). A sobrevivencia foi superior a 90% nas tres densidades testadas. A tecnologia de bioflocos pode ser empregada no cultivo intensivo da tilapia do Nilo O. niloticus na fase de engorda, utilizando-se densidades de estocagem de 45 peixes.m-3.

FONTES DE CARBONO E RELAÇÕES C:N NA QUALIDADE DA ÁGUA NO CULTIVO DE TILÁPIA DO NILO EM SISTEMA DE BIOFLOCO

The use of biofloc technology (BFT) can improve fish production in regions with low water availability. Therefore, information on dynamics of water quality is essential for success in fish rearing. Thus, the objective of the present study was to evaluate the water quality for Nile tilapia farming in a system without water exchange, during the fingerling stage, using different sources of carbon and C:N ratios. A completely randomized experimental design was used in a 2x3 factorial arrangement, with two carbon (C) to nitrogen (N) ratios (10:1 and 20:1) and three carbon sources (sugar, molasses and cassava starch). The C:N ratio and carbon source affected the variables alkalinity, settleable solids (SS), turbidity and total suspended solids (TSS), showing significantly higher values at C:N ratio of 20:1 (P < 0.05). The best carbon source for microbial floc formation were the molasses and sugar, under C:N ratios of 10:1 and 20:1. The stability of the monitored water quality parameters occurred from 6 to 7 weeks of rearing. The growth performance of Nile tilapia in BFT system fertilized with different organic carbon sources was not significantly different (P < 0.05) between treatments. The use of molasses to fertilize BFT systems can reduce costs of production in regions where this product is available.

CULTIVO DO CAMARÃO MARINHO, SOB DIFERENTES DENSIDADES DE ESTOCAGEM E ALIMENTAÇÃO, EM ÁGUAS OLIGOHALINAS

The cultivation of Litopenaeus vannamei has increased in inland areas by using low salinity waters. Cultivation techniques in coastal waters are well developed, however, studies for low salinity conditions are needed, especially regarding the ideal ionic composition of water and its effects on the zootechnical indices. Brazil has adopted this strategy and the semiarid region showed great potential due to its favorable climate and water conditions. Thus, experimental cultivations were conducted in Serra Talhada, State of Pernambuco, in order to evaluate the influence of two feeding strategies (with and without feeding) and three cultivation densities (5, 10 and 15 shrimps m), on the production variables of this species. Three ponds of 280 m were built, in which six nursery nets of 20 m were installed. The cultivation was performed with juvenile shrimps of 8.53 g and lasted 50 days. The animals were fed twice a day with commercial feed containing 25% of crude protein. The water quality (salinity ~1.0 g L, temperature ~28.09°C, pH ~8.48) and the shrimp growth were monitored with weekly biometry during the cultivation. A significant difference was found only in the treatment without feeding with 15 shrimps m, the average final weight of all treatments ranged from 13.16±1.33 g to 15.50±1.66 g. The survival rates were high in the treatments with feeding and its variation between treatments was 60.56±6.76% and 83.00±4.00%.