A viola é atualmente a espécie de peixe de maior valor econômico da Lagoa Mangueira e, tendo em vista este fato, o objetivo deste trabalho foi analisar seu rendimento corporal e a composição química do filé. Quarenta animais capturados na Lagoa Mangueira foram divididos em dois grupos de 20 animais cada. O peso apresentou uma variação de 128 a 190g no grupo A e de 234 a 293 g no grupo B. A avaliação biométrica foi realizada no Laboratório de Ictiologia da UFPEL, onde os animais foram medidos em comprimento e peso, sendo utilizadas para o cálculo de rendimento corporal. Foram avaliados o rendimento de carcaça, rendimento de cabeça, rendimento visceral, rendimento da pele, rendimento de tronco limpo e rendimento de filé. A análise de composição química foi realizada com filé seco, para se obter os resultados de proteína, extrato etéreo, cinzas e umidade, e na matéria natural para se obter o teor de ácidos graxos. O peso dos animais influencia no rendimento de carcaça. O filé da viola é considerado magro, com alto teor de proteína e maior quantidade de ácidos graxos insaturados em comparação aos saturados.

Loricariichthys anus (Viola) is currently the largest fish species of economic value of Mangueira Lagoon and, because of that, the aim of this work was to analyze its body yield and the chemical composition of its fillet. Forty animals caught in Mangueira Lagoon were divided into two groups of 20 animals each. The weight presented a variation of 128 to 190g in group A and of 234 to 293g in group B. Biometric evaluation was performed in Ichthyology Laboratory of UFPEL, where the animals were evaluated regarding length and weight, which were used for body yield calculation. Carcass yield, head yield, visceral yield, skin yield, clean trunk yield and fillet yield were evaluated. Chemical analysis was performed in dried fillet to obtain the values of protein, lipids, ash and moisture, and in natural matter to assess the fatty acid content. The weight of animals affects carcass yield. The viola fillet is lean, with high protein content and higher amount of unsaturated fatty acids compared to saturated.

To determine the available phosphorus requirement of pejerrey fish, four semi-purified diets were formulated to contain increasing available phosphorus levels (0.90, 2.7, 5.7 and 8.3 g/kg). Each diet was assigned to groups of 10 fish with average weight of 1.26±0.17 g, distributed into a completely randomized design with four treatments and four replications. Fish were fed at a rate of 10% total biomass four times a day for 60 days. The parameters productive performance, body chemical composition and mineral composition of bones and scales were evaluated. The best productive performance of fingerlings was obtained with the diet containing 4.3 g/kg available phosphorus. The average level of 6.3 g/kg available phosphorus promotes better mineralization of bones and scales in pejerrey fish.