The jundiá or silver catfish (Rhamdia quelen Quoy & Gaimard, 1824) is species native to the Americas, omnivorous, with a tendency towards carnivorous feeding habits. The species presents commercial potential, and therefore, knowledge on its nutritional requirements, as well as basic feed ingredients, is essential. Its tendency towards carnivorous feeding habits leads to some concerns regarding plant ingredient digestion abilities, although rice, soybean, flax, sorghum, ground corn or oat bran can be used as feed ingredients for this species, since they present good digestibility coefficients. In order to guarantee adequate performance of metabolic, immunological and reproductive functions, jundiá feed can be supplemented with micronutrients that minimize the effects of antinutritional factors present in plant ingredients. Plant ingredients present several economic advantages such as suitable quality, competitive prices and the fact that they are widely available in South Brazil.

The aim of this study was to determine the apparent digestibility coefficients and digestible values of crude protein, ethereal extract, gross energy and dry matter of mulberry leaf meal (MLM) (Morus alba L.) as Nile tilapia (Oreochromis niloticus) feed. A total of 135 Nile tilapia juveniles were used, and the indirect methodology (Cr2O3) was applied for digestibility determinations. Mulberry leave meal presented good apparent digestible coefficients of protein, ethereal extract and energy with respective values of 0.94, 0.58 and 0.39. The mulberry leave meal thus comprises adequate digestible protein and digestible energy values, similar or better than other leafy foods, presenting potential for inclusion in Nile tilapia diets.

- An experiment lasting 180 days was carried out to evaluate the influence of sex on the performance and production of silver catfish (Rhamdia quelen) when reared in closed recirculation systems using only males, only females, or with both genders. A total of 300 fish (41.49 ± 6.82 g and 16.53 ± 0.95 cm) were used, comprising 150 females and 150 males distributed in an experimental structure consisting of three closed water recirculation systems coupled to a 20,000 L culture tank and a 20,000 L biofiltration tank connected by a 3,500 L h-1 water pump. The first system contained 100 females, the second, 100 males, and the third, 50 females and 50 males. High fish weight variations were observed regardless of sex. Female weight gains and specific growth rates were 41.51 % and 28.94 % higher compared to males, respectively, exhibiting greater growth than males raised monosexually or in mixed rearing systems, with no effect on chemical composition or trunk yield. The findings thus indicate that both male and female silver catfish exhibit wide weight variations and females that gain more biomass than males reared monosexually or in mixed-sex systems.

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