Optimización del tratamiento térmico para la inducción al desove de Argopecten purpuratus (Mollusca: Bivalvia)

Based on methodologies currently used in commercial hatcheries, four thermic treatments were compared to induce the gametes expulsion of Argopecten purpuratus. The treatments evaluated included: 1) gradual increase in temperature, 2) gradual decrease, 3) 5 °C thermal-shock, 4) 10 °C thermal-shock and 5) control at constant temperature 16 °C. After induction, the number of fertilized oocytes in each treatment was estimated. The results show that a gradual increase in temperature between 16 and 26 °C causes a significantly higher proportion of fertilized oocytes compared to other treatments

Perfil de ácidos grasos y contenido energético en músculo de juveniles de cabrilla (Paralabrax humeralis) acondicionados al cautiverio

The fatty acids profile and energy content in muscle of juveniles of Paralabrax humeralis conditioned at three temperatures (12, 17 and 22 °C) for a period of 90 days was evaluated. For this purpose, 2 m3 fiberglass tanks connected to water recirculation systems with temperature control were used. The fishes were fed with commercial balanced feed (pellets) of 4 mm diameter, 42% protein and 12% fat twice a day. Every 30 days the weight and length of all fishes was recorded. In addition, six fish per acclimation temperature were sacrificed to measure fatty acids concentrations and energy content of muscle tissue. The observations showed that P. humeralis quickly accepts the artificial feed reaching a 95% survival during the evaluation period. The muscle concentration of linoleic and linolenic acids increased more than 100% in the three temperature groups. Contrarily, the concentration of docosahexaenoic acid (DHA), arachidonic acid (ARA), docosapentaenoic acid (DPA) and eicosapentaenoic acid (EPA) decreased by 48, 45, 26 and 20% respectively. The energy content in muscle increased 13% during the conditioning period. It is concluded that P. humeralis adapts quickly to the conditions of captivity; however, the feed provided must contain higher amounts of ARA, EPA, DPA and DHA.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

Embryonic development and effect of temperature on larval growth of the Peruvian anchovy Engraulis ringens

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)

Preferencia y tolerancia térmica de juveniles de chita Anisotremus scapularis (Pisces: Haemulidae)

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.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.