Effects of liming and development of Curimbatá (Prochilodus lineatus) larvae on the abundance of zooplankton in fish ponds

Abstract

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 "Curimbatá". 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 < 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.

Trophic relationship between the Patinga hybrid (Piaractus mesopotamicusxPiaractus brachypomus) andEchinorhynchus gomesiMachado Filho, 1948 in fish farms

“…When zooplankton density was evaluated, Rotifera was shown to be dominant in P2, whereas Copepoda and Ostracoda groups were strongly represented in P1. In general, the zooplankton community can be influenced by water quality, food availability, ecological interactions (competition and predation between the organisms), and in the case of cultivation environments, tank management (Paes et al, 2011;Sipaúba-Tavares et al, 2008).…”

Freshwater parameters in the state of Rio Grande do Sul, southern Brazil, and their influence on fish distribution and aquaculture

“…The increase in alkalinity from 30 to 130 mg CaCO 3 L -1 without a change in pH or water hardness only decreased growth of R. quelen juveniles maintained at high stocking densities (Andrade et al, 2007). Larvae of P. lineatus and O. niloticus had better growth at an alkalinity of 30 mg CaCO 3 mg L -1 compared to 15-20 and 55-60 mg CaCO 3 mg L -1 (Rojas et al, 2001;Rojas & Rocha, 2004;Paes et al, 2011), but these studies used hydrated lime (CaCO 3 .2H 2 O) to increase alkalinity, which also changed water hardness. The increase in alkalinity from 22 to 80 mg CaCO 3 mg L -1 with the addition of Na 2 CO 3 (without changing water hardness) did not affect any growth parameter of male sex reversed juveniles of O. niloticus (Cavalcante et al, 2010) nor improved growth of those raised in acidic water (Cavalcante et al, 2012), demonstrating that for this species water hardness is more important.…”