RESUMEN. Dormitator latifrons es un pez con potencial comercial que habita ambientes con climas tropicales y subtropicales desde el sur de California (EEUU) hasta Perú. El objetivo fue determinar los requerimientos nutricionales de proteína y lípidos para el crecimiento de juveniles, se elaboraron cuatro dietas experimentales con contenidos de proteína del 30 y 40%, y lípidos del 8 y 16%, con tres repeticiones por tratamiento. Se realizó el análisis proximal de las dietas experimentales, del músculo al inicio y al nal del experimento y se determinó la digestibilidad aparente. No se detectaron diferencias signicativas (p > 0.05) en el crecimiento, supervivencia y la composición proximal del músculo de los peces. La digestibilidad aparente de la dieta con 30% de proteína y 8% de lípidos fue signicativamente superior al resto de las dietas, por lo que se considera suciente para un adecuado crecimiento de juveniles de D. latifrons.ABSTRACT. Dormitator latifrons is a sh with commercial potential that inhabits environments with tropical and subtropical climates from southern California (USA) to Peru. The objective was to determine the nutritional requirements of protein and lipids for the growth of juveniles; four experimental diets were prepared with protein contents of 30 and 40%, and lipids of 8 and 16%, with three repetitions per treatment. Proximal analysis of the experimental diets, of the muscle at the beginning and at the end of the experiment, was carried out and the apparent digestibility was determined. No signicant dierences (p > 0.05) were detected in the growth, survival and proximal composition of the sh muscle. The apparent digestibility of the diet with 30% protein and 8% lipids was signicantly higher than the rest of the diets, so it is considered sucient for adequate growth of D. latifrons juveniles.

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We analyzed the occurrence of morphotypes in the males of Macrobrachium tenellum (Smith, 1871), a species of potential use in farming, using biometric data and multivariate statistical analysis. Specimens were collected in the Ameca River, Mexico and grown for four months in two rectangular concrete ponds 50 m2 at an initial density of 10 individuals m–2. A biometric analysis was done on all male specimens, identified by the presence of the appendix masculina on the second pair of pleopods. We measured eight dimensions in each of the measured male specimens. Color and spination of the right second cheliped were also determined. We performed a statistical analysis of the data using multivariate analysis, which resulted in the identification of five morphotypes: dark-brown claw (DBrC), brown claw (BrC), cinnamon claw (CC), translucent claw (TC), and small male (SM). The mean of groups of almost all variables showed statistically significant differences except for the ratio Lcl:Lpo. There was no significant difference between groups BrC and DBrC, and spine angles were not significant between groups CC versus TC and BrC. A detailed description of the main macroscopic characteristics that differed between morphotypes is provided, which will allow their identification in future work. Our results will also help in studying social interactions between the male morphotypes.

The aim of this study was to determine the effect of stocking density on growth performance, survival, feeding efficiency, and size distribution of the freshwater, longarm river prawn Macrobrachium tenellum during the nursery phase of intensive culture in a net cage–pond system. Juvenile longarm river prawns (mean weight = 0.46 g) were cultured in 12 net cages (1 m3) within two circular ponds (20.52 m3 each) at stocking densities of 50, 100, 200, and 400 prawns/m3. Final length, final body weight, weight gain, growth rate, and specific growth rate were found to be significantly better at a stocking density of 50 prawns/m3. A greater variation of sizes was observed at the density of 50 prawns/m3, with less in the highest density (400 prawns/m3). The results of the study showed that longarm river prawns in the nursery phase can be cultivated with a stocking density of 100 prawns/m3 to obtain a mean final weight of 1.6 g. This is the minimum size needed to obtain a high survival rate in the grow‐out stage in ponds. However, the best growth performance and survival were registered in the densities of 50 and 100 prawns/m3.