Rearing of the Amazon catfish Pseudoplatystoma punctifer (Castelnau, 1855): weaning with dry and moist diets

The aim of this study was to compare the effects of dry and moist diets at weaning on growth, survival and incidence of cannibalism in the Amazon catfish Pseudoplatystoma punctifer. Three moist diets (MCD: moist commercial diet; MCPD: moist commercial peptide enriched diet; BLD: bovine liver enriched diet) and a dry diet (CDD: commercial dry diet) were used to feed fingerlings reared in 40-L tanks (30-L water volume; three replicates per treatment; stocking density: initial 1500 larvae per tank, from 18 days post-fertilization, dpf (17 days post-hatch, dph) onwards 210 juveniles per tank; photoperiod 0L:24D) in a recirculation water system (27.9 ± 0.5°C). Fish were fed Artemia nauplii at 20% of the larval biomass from 4 to 19 days post-fertilization (dpf) and then weaned onto the four experimental diets within 3 days in the moist diets and within 6 days in the dry diet. At 33 dpf, feeding of groups fed the moist diets was switched to the dry diet within 2 days. Results showed higher (58.6 ± 10%) and lower (4.7 ± 0.7%) survival rates in BLD and CDD groups, respectively, the latter showing the highest occurrence of type II cannibalism. Although weaning was achieved in all dietary groups, the moist diets MCD and MCPD showed better growth results both in terms of total length and wet weight. This study showed that, among the tested diets, the moist diets seem to be more adequate for early juvenile P. punctifer.