We analyzed the reproductive cycle of females of the palaemonid shrimp Macrobrachium tenellum (Smith, 1871) collected in the Ameca River, between the Jalisco and Nayarit states, Mexico. We studied the seasonal occurrence of ovigerous females during the year, their relationship with abiotic factors, and the size of the first sexual maturity. The study included 7,100 specimens of M. tenellum, of which 2,791 (39.3%) were males, 3,559 (50.1%) females, and 750 undifferentiated (10.6%). The sex ratio of the total (male-female) population differed significantly from the expected 1:1 with more females. A total of 309 females carried eggs (8.7% of all collected females). Ovigerous females, which were collected in three of the four sampling sites, were found almost year-round (with the exception of March and December), and their number showed a significant positive correlation with water temperature and rainfall. The size of first maturity (TL50%) for all collected females was 55.7 mm total length (TL), ranging from 64.3 mm TL to 42.7 mm TL. The results revealed that the population of M. tenellum in the Ameca River has a continuous reproductive period associated with the rainy season and increasing water temperature.

In recent years, the partial and total substitution of fishmeal (FM) with by-product meals has reduced feed manufactory and aquaculture industry production costs. The present work aimed to determine the effects of the substitution of FM by hydrolyzed feather meal (HFM) in the diet of Macrobrachium tenellum. Four isoproteic and isolipidic diets were prepared, substituting 0, 33, 67, and 100% of FM with HFM. These diets were used to feed M. tenellum juveniles for 60 days. The results of the biological indices, in terms of weight, final length, and specific growth rate, did not show significant differences between the treatments (P ˃ 0.05). The lowest survival index (35 ± 13) is observed in the 100HFM treatment, showing significant differences from the 33HFM treatment (65 ± 13). However, the 67HFM and 100HFM treatments, associated with the lowest values of the biological indices, indicated a decreasing trend. No significant differences were observed in the proximate composition of the muscle between the four treatments. The average values of the four treatments were 33.5% protein, 3.7% lipid, and 18.2% ash. However, the fatty acid profile observed significant differences between the treatments. As the content of HFM increased, the concentration of some fatty acids, such as C14:0, C16:0, C20:5n3, and C22:6n3, decreased, while the content of C18:1n9 and C18:2n6 increased. The results showed that it is feasible to substitute between 33 and 67% of FM with HFM in feed diets for river prawns.

Introducción: Las corrientes de arroyos y ríos son señales naturales que influencian las migraciones en el ciclo de vida de langostinos anfídromos. Objetivo: Evaluar el comportamiento de reotaxis en juveniles y adultos de Macrobrachium tenellum, con relación a su capacidad de respuesta a diferentes velocidades de flujos de corriente de agua en un sistema experimental de circuito cerrado. Métodos: Se utilizó un sistema de tubos PVC, con una tina para la recirculación del agua y un remanso colocado a la mitad del sistema. Se probaron flujos de agua de 10-30 cm/s para establecer las condiciones experimentales. Se evaluó el comportamiento de reotaxis sin remanso (SR) y con el remanso (CR); se probaron tres flujos de agua: FI, 14 cm/s; FII, 18.7 cm/s; y FIII, 22.1 cm/s, y un flujo control FC, 0 cm/s, con 40 juveniles, 40 hembras y 40 machos por flujo. Se identificaron tres comportamientos principales: reotaxis positiva, reotaxis negativa y sin reacción. Resultados: Tanto para SR como CR los flujos de agua estimulan mayormente la reotaxis positiva y la respuesta de comportamiento es diferente según la velocidad del flujo de agua y si son juveniles, hembras o machos. En CR hubo una mayor respuesta de los langostinos a seguir nadando en contra de la corriente cuando estos ingresaban al remanso. En un ángulo recto, el flujo de agua constante superior a 23.2 cm/s dificulta el nado contra corriente de esta especie. Conclusiones: La respuesta de reotaxis positiva fue la que mayor predominó en juveniles, hembras y machos de M. tenellum.

One way to approach the nutritional requirements of native shrimp, necessary to consolidate their culture, is to know their biochemical composition. The effect of feeding two levels of lipids (4 and 12% L) and four levels of proteins (30, 35, 40 and 45% P) in M. tenellum females was evaluated with respect to the biochemical composition of their eggs (EG), larvae (LR), gonad (GO) and hepatopancreas (HP). Total protein (TP), total carbohydrate (TC) and total lipid (TL) were estimated. In EG, L and P levels influence TP and TL; TP increases in diets higher than P35. In LR, there are no differences (p > 0.05) in TP and in TL, only diets L4P40 and L12P30 were different (p < 0.05). In GO, there is no trend in TP differences; in TC there was variation in the range of the data and TL was higher in L4P30 and L4P35. In HP, the diets with L4 obtained the highest TP values (p < 0.05); the L12 diets were higher in TL (p < 0.05). In general, diets with an inclusion of L12 showed the highest TP, TC and TL means, within this lipid level the P30 diet stood out; therefore, it is recommended to use a diet with L12P30 in the formulation of balanced feed for the species.