Protótipo de tanque-berçário para criação intensiva de larvas de pirarucu

Abstract

Larviculture is a challenge in arapaima farming, however several advances have been achieved in recent years. In intensive larviculture carried out in the laboratory, fish larvae are housed in tanks with different geometric shapes (square, rectangular, circular and trapezoid-circular), there is not a specific model of tank for arapaima larvae. The aim of this work was to develop a prototype tank in the shape of a circular crown, without the central area, specific for intensive larviculture of arapaima. After the planning and construction of the experimental tanks, an feeding assay was carried out with arapaima larvae in a completely randomized design with two treatments and five replications, as follows: test tank in circular crown format and conventional tank (circular). Arapaima larvae (0.21 ± 0.03 g; 3.58 ± 0.18 cm) were homogeneously housed in the experimental units, with a useful volume of 150L and a density of 300 larvae/tank in a recirculation system with phytoremediation, constant artificial aeration and natural photoperiod. Fish were fed eight times daily during 29 experimental days. The larvae were fed exclusively with Artemia nauplii during the first 3 days. On the 4th day, the feed transition was started by co-feeding by supplying Artemia nauplii and commercial crushed feed (Artemia nauplii + feed + water), in the proportion of 13% of the biomass for 9 days. After the feeding transition, the larvae were already trained to eat dry crushed feed. At the end of the experiment, we evaluated the zootechnical performance, parasitological analysis and cost of production of the larvae. Variables with parametric data were compared by Student's t test and those with non-parametric data by the Mann-Whitney U test (p<0.05). Fish raised in the test tank showed lower survival than those raised in the conventional tank (70.7% and 92.7%, respectively). However, the larvae reared in the test tank showed greater weight gain 2.14 ± 0.15 g, total length 6.97 ± 0.17 cm and a relative growth rate of 9.35 ± 0.25 %/day, probably due to the highest concentration and availability of food for test tank larvae. In the test tank, fish presented higher intensity of Trichodina sp. in the gills and mucus due to the accumulation of organic matter, especially after the feeding transition period. The conventional tank provided higher net income due to the indoor larviculture due to the higher survival rate. Test tank format can be used in the phase in which the larvae are receiving only live food, when food accumulation is not a problem. It is suggested adjustments in tank test to improve water circulation, to eliminate excess organic matter from the inert diet.