科研之友
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摘要
AIM: We aimed to evaluate the influence of the correction of the water alkalinity in the fish ponds on the density of zooplankton under a period they were stocked with larvae of Prochilodus lineatus, a neotropical fish called %26quot;Curimbat芍%26quot;. METHODS: We used a factorial design completely randomized. In one plot (2 ponds) there was no correction of the alkalinity of the water (20 mg CaCO3.L-1) and in two others, this variable was adjusted weekly to values around 30 and 60 mg CaCO3.L-1 1, with two replicates each. Zooplankton was sampled weekly and the experiment lasted 63 days. RESULTS: Significant differences in the density of the zooplankton over time (F = 6.78, p %26lt; 0.05) were found and there was a sharp decrease in zooplankton density from first to second week, and successive small increases in density from the fourth week until the end of the experiment. When considering the entire study period, alkalinity correction 60 mg CaCO3.L-1 resulted in higher density of zooplankton. Great changes in zooplankton composition occurred. Rotifera were dominant at the beginning of the experiment and Cladocera and Copepoda in the later weeks possibly due to an interplay of dilution by rain and fish predation in the initial part of the experiment and due to both alkalinity correction and predation by both fish and predatory copepods from the fourth week until the end. CONCLUSION: The experiment corroborated the hypothesis that correction of water alkalinity in ponds does favor zooplankton development but also highlighted biotic and abiotic interaction of factors operating simultaneously. OBJETIVO: Nosso objetivo foi avaliar a influencia da corre o da alcalinidade da 芍gua em viveiros de piscicultura na densidade do zooplancton em per赤odo em que foram estocados com larvas de Prochilodus lineatus, um peixe neotropical denominado %26quot;Curimbat芍%26quot;. M谷TODOS: Foi utilizado um delineamento experimental fatorial, inteiramente causualizado. Em um tratamento (2 viveiros), n o houve corre o da alcalinidade da 芍gua, e em outros dois viveiros, a alcalinidade foi ajustada semanalmente para valores em torno de 30 e 60 mg CaCO3.L-1, com duas r谷plicas cada. Os organismos zooplanct nicos foram coletados semanalmente durante 63 dias. RESULTADOS: Diferen as significativas foram observadas na densidade do zooplancton ao longo do tempo (F = 6,78, p %26lt; 0,05) e um decr谷scimo acentuado na densidade do zooplancton foi observado da primeira para a segunda semana, e pequenos aumentos sucessivos na densidade da quarta semana at谷 o final do experimento. Ao considerar todo o per赤odo experimental, a alcal
