-40). Las evaluaciones biométricas muestran que mayor crecimiento, conversión alimentaria y factor de condición se obtuvieron en A. scapularis alimentadas con la dieta DM-48 (P < 0,05). Sin embargo, la relación talla-peso y consumo de alimento-talla fueron similares entre los tratamientos dietarios. Por otro lado, menores concentraciones de proteína y mayores de lípidos se obtuvieron en el músculo de juveniles de A. scapularis alimentados con las dietas DM-48 y DF-50 (P < 0,05), respectivamente. El análisis de componentes principales mostró una mayor correlación entre peces alimentados con la dieta DM-48 y el contenido muscular de DHA, EPA y ARA; y con el crecimiento. Los resultados sugieren que la formulación de alimentos para juveniles de A. scapularis debería contemplar al menos de 48% de proteína y concentraciones importantes de DHA, EPA y ARA para su adecuado crecimiento de esta especie. Palabras clave: Anisotremus scapularis, Haemulidae, chita, ácidos grasos esenciales, maricultura.Evaluation of commercial diets on growth and its effect on muscle biochemical composition of juvenile Peruvian grunt, Anisotremus scapularis (Tschudi, 1846) (Familia: Haemulidae)ABSTRACT. The growth, muscle proximal composition and fatty acid profile of juveniles of Anisotremus scapularis fed with four commercial diets were evaluated. During 106 days, 200 fishes, were distributed in four treatments, fish were fed with commercial diets identified by their protein content: 50% (DF-50), 48% (DM-48), 44% (DT-44) and 40% (DT-40). Biometric evaluations showed that higher growth (P < 0.05), feedconversion and condition factor were obtained in A. scapularis fed with DM-48. However, both length-weight and food intake-size relationships were similar among dietary treatments. Lower (P < 0.05) protein and higher (P < 0.05) lipid concentrations in muscle of A. scapularis fed with DM-48 and DF-50 were obtained, respectively. Principal component analysis showed a higher correlation between fishes fed with DM-48 and DHA, EPA, and ARA muscle contents as with growth. Our results suggest that the food formulation for juveniles of A. scapularis should include at least 48% protein and significant concentrations of DHA, EPA and ARA for a proper growth of this species.

Understanding aspects of the biology of early life stages of marine fish is critical if one hopes to reveal the factors and processes that impact the survival and recruitment (year class) strength. The Peruvian anchovy (Engraulis ringens) is a key species in the Humboldt current system, and the present study provides the first description of the embryonic and larval development of this species reared in captivity. Embryonic and early exogenous feeding stages of larvae were illustrated in detail at 18.5°C. Hatching was completed within 42 and 48 h post‐fertilization at 18.5 and 14.5°C, respectively. Mean ± 95% C.I. standard length (LS) at hatch (3.40 ± 0.10 mm at 18.5°C and 2.76 ± 0.34 mm at 14.5°C) was significantly different between the two temperatures. Larval behaviour was assessed at 18.5°C; at the onset of exogenous feeding [3 days post‐hatch (dph)], larvae were fed small, motile dinoflagellates, Akashiwo sanguinea. At 7 dph, larvae started to feed almost exclusively on zooplankton (rotifers and Artemia nauplii). Larval activity increased with age, and the first sign of schooling was noted at 31 dph (18.56 mm LS) at 18.5°C. Temperature had a significant effect on size‐at‐age, but not on body shape (depth to LS ratio). The size‐at‐age data for larvae (this study) was used to parameterize a temperature‐corrected von Bertalanffy growth function for Peruvian anchovy, the accuracy of which was assessed for juveniles and adults (literature values).

Abstract.-Thermal preference and tolerance of juvenile Anisotremus scapularis (Pisces: Haemulidae) at different acclimation temperatures (14, 17 and 22°C) were evaluated in order to estimate the optimum temperature and the thermal tolerance limits of this species. The preference was determined through acute preferred temperature. Maximum critical temperature and mean lethal temperature allowed to estimate thermal tolerance. The results show that acclimation temperatures higher than 14°C increase both thermal preference and tolerance. However, individuals acclimatized to 22°C preferred temperatures lower than their acclimation. In addition, thermal tolerance was identical between individuals acclimatized at 17°C and 22°C. The optimum temperature of juvenile A. scapularis was 18.7 ± 2°C and its upper and lower tolerance limit was 32.6 and 10.1°C, respectively. Based on the results, we concluded that a temperature of 18.7 ± 2°C would optimize the physiological processes in juvenile A. scapularis and that temperature higher than 32.6°C and lower than 10.1°C would cause the immediate death of the organism.Key words: Anisotremus scapularis, thermal preference, thermal tolerance, acclimation temperature, optimum temperatureResumen.-Se evaluó la preferencia y tolerancia térmica de juveniles de Anisotremus scapularis (Pisces: Haemulidae) a diferentes temperaturas de aclimatación (14, 17 y 22°C) con el fin de estimar la temperatura óptima y los límites térmicos de tolerancia de esta especie. La preferencia fue determinada mediante el método de temperatura preferida aguda. La tolerancia fue estimada mediante la temperatura crítica máxima y la temperatura letal media. Los resultados muestran que temperaturas de aclimatación mayores a 14°C incrementan la preferencia y tolerancia térmica de la especie. Sin embargo, individuos aclimatados a 22°C prefieren temperaturas menores a su aclimatación y limitan su tolerancia con respecto a los individuos aclimatados a 17°C. La temperatura óptima estimada para juveniles de A. scapularis fue de 18,7 ± 2°C y su límite térmico superior e inferior de tolerancia fue de 32,6 y 10,1°C, respectivamente. En base a los resultados se concluye que una temperatura de 18,7 ± 2°C optimizaría los procesos fisiológicos en juveniles de A. scapularis, y que temperaturas mayores a 32,6°C y menores a 10,1°C ocasionarían la muerte inmediata del organismo.

Se evaluó el perfil de ácidos grasos y contenido energético en músculo de juveniles de Paralabrax humeralis acondicionados a tres temperaturas (12, 17 y 22 °C) por un periodo de 90 días. Se utilizaron tanques de fibra de vidrio de 2 m3 conectados a sistemas de recirculación de agua con control de temperatura. Los peces recibieron dos veces al día alimento balanceado comercial (pellets) de 4 mm de diámetro, 42% de proteína y 12% de grasa. Cada 30 días se registró el peso y longitud de todos los peces. Además, seis peces por temperatura de aclimatación fueron sacrificados para medir las concentraciones de ácidos grasos y el contenido energético del tejido muscular. Las observaciones muestran que P. humeralis acepta rápidamente el alimento balanceado alcanzando una sobrevivencia del 95% durante el periodo de evaluación. La concentración muscular de ácidos linoleico y linolénico aumentaron más del 100% en los tres grupos der temperatura. Contrariamente, la concentración de ácidos docosahexaenoico (DHA), araquidónico (ARA), docosopentaenoico (DPA) y eicosapentaenoico (EPA) disminuyeron en 48, 45, 26 y 20%, respectivamente. El contenido energético en músculo aumentó 13% durante el periodo de aclimatación. Se concluye que P. humeralis se adapta rápidamente a las condiciones de cautiverio; sin embargo, el alimento proporcionado debe contener mayores cantidades de ARA, EPA, DPA y DHA.

Hypoxia is currently one of the greatest threats to coastal ecosystems worldwide, generating massive mortality of marine organisms, loss of benthic ecosystems and a decrease in fishery production. We evaluated and compared the tolerance to hypoxia of two species from different habitats of the Peruvian coast, the Peruvian rock seabass Paralabrax humeralis and the Peruvian grunt Anisotremus scapularis. The effect of hypoxia was measured as a function of the exposure time (progressive and chronic) on the behavioural and physiological responses of the two species, as well as on the enzymatic activity associated with the oxidative stress response of lactate dehydrogenase (LDH), superoxide dismutase (SOD) and alkaline phosphatase (AKP). The ventilatory frequency was measured at two different temperatures (16 and 22°C) under progressive hypoxia conditions to determine the ventilatory critical point (Vcp). A. scapularis showed a higher Vcp than P. humeralis, which was positively affected by temperature. The median lethal time of A. scapularis was 36 min at 60% of oxygen saturation, while P. humeralis showed no mortality after 31 days of exposure at 5% oxygen saturation. Different enzymatic activity (P < 0.05) between species under hypoxia was recorded, in SOD (gill and muscle) and AKP (blood). A general tendency, under hypoxia, to slightly increase LDH activity (except for blood in A. scapularis, P < 0.05) and SOD activity (mainly in muscle of A. scapularis, P < 0.05), and decrease AKP activity (mainly in liver of P. humeralis, P < 0.05) was observed. The response of P. humeralis to hypoxia goes through a reduction in activity and metabolism, so this species can be considered hypoxia‐tolerant, allowing it to face hypoxia events during prolonged periods. On the other hand, A. scapularis response to hypoxia prioritizes avoidance mechanisms and, together with other adaptations, makes it especially vulnerable to hypoxia and able to be considered hypoxia‐intolerant.