Interest of mussel hatchery development has increased during the last years as natural seed collection does not always satisfy the demand of producers. Success on larval bivalve culture depends on several factors such as diet, temperature or stocking density. In this study, the effect of larval density in mussel culture success has been assessed testing three larval densities: high (50 larvae mL À1 ), medium (25 larvae mL À1 ) and low (5 larvae mL À1 ). Results showed higher growth and survival at low density but the amount of postlarvae was low. The highest number of settled larvae was observed at high density but mortality was also high and a delay on the larval development was detected producing a prolongation on the culture length. However, medium density resulted in a good survival and growth and also in a considerable amount of postlarvae, as this density could be adequate for massive mussel seed production. Cortisol content on the larvae and postlarvae was also analysed and significant differences were obtained among groups probably due to the stress associated to settlement and metamorphosis.

High paralarvae mortality is a major bottleneck currently hindering the control over the lifecycle of common octopus (Octopus vulgaris Cuvier, 1797). It is believed that this problem might be related to either zoo-technical and/or nutritional aspects. The present paper is focused on the study of different zoo-technical aspects related to light conditions on the rearing of paralarvae, including the effects of polarization in prey ingestion, the use of a blue filter to simulate natural conditions, and the use of focused light to avoid reflections of the rearing tank's walls. In the first experiment, O. vulgaris paralarvae ingestion of Artemia sp. and copepods (Tisbe sp.) was assessed under either normal or polarized light. In the second experiment, the effect of a blue filter with natural light or focused artificial light on growth and mortality was assessed over 15 days of rearing. Ingestion rate was not influenced by light polarization. Nonetheless, a significantly higher ingestion of Artemia sp. with respect to copepods was observed. The blue filter promoted the use of natural light conditions in Octopus paralarval culture, while focused light reduced the collision of the paralarvae against the walls. However, no significant differences were found in paralarval growth nor survival.

RESUMEN.Mytilus chilensis tiene ciclos reproductivos que varían latitudinalmente. Presenta reducida diferenciación genética y morfológica debido a un gran potencial de dispersión. Se acondicionaron reproductores de bahía Yaldad (Chiloé) y bahía Zenteno (Punta Arenas) a 9 ± 0,5°C y 15 ± 0,5ºC, alimentados con dieta (1:1) de Isochrysis galbana y Chaetoceros neogracile. Se espera dilucidar si el acondicionamiento a diferentes temperaturas produce variaciones en el potencial reproductivo de las poblaciones. El menor desarrollo gonadal se produjo en los reproductores acondicionados a 9ºC, mientras que el mayor se produjo en los reproductores acondicionados a 15ºC provenientes de Chiloé. La fecundidad de los reproductores de Yaldad fue mayor que los de Zenteno. El diámetro de los ovocitos fue mayor en los reproductores de Zenteno y en ambas poblaciones fue mayor a 9ºC. Ni el porcentaje de huevos fecundados ni el porcentaje de eclosión de larvas D mostraron diferencias significativas entre las poblaciones a ninguna de las temperaturas de acondicionamiento. De acuerdo con estos resultados, no se logra establecer diferencias en el potencial reproductivo en las poblaciones y bajo las condiciones de este estudio. Palabras clave: acondicionamiento, mitílidos, potencial reproductivo, temperatura, índice de condición, Chile. Assessment of the reproductive potential of the mussel (Mytilus chilensis) from two natural populations subjected to different conditioning temperaturesABSTRACT. The reproductive cycles of Mytilus chilensis vary latitudinally. This species has reduced genetic and morphological differentiation due to its high potential for dispersal. Broodstocks from Yaldad Bay (Chiloé) and Zenteno Bay (Punta Arenas) were conditioned at 9 ± 0.5°C and 15 ± 0.5°C, and were fed a diet (1:1) of Isochrysis galbana and Chaetoceros neogracile. We expected to determine whether conditioning at different temperatures produces changes in the reproductive potential of the populations. Gonadal development was lowest in the broodstocks conditioned at 9ºC, and highest in those conditioned at 15°C, from Chiloé. Fertility was greater in broodstocks from Yaldad than in those from Zenteno. Oocyte diameter was greater in broodstocks from Zenteno, and both populations showed larger diameters at 9ºC. Neither the percentage of fertilized eggs nor the percentage of larvae hatching differed significantly between populations at either conditioning temperature. Therefore, it was not possible to establish differences in the reproductive potential of the populations under the conditions studied herein.

ABSTRACT. D-veliger larvae from Mytilus chilensis broodstocks from natural banks of Punta Arenas and Chiloé (Chile) were grown at 9 ± 0.5 ºC and 15 ± 0.5 ºC to compare results under two culture temperatures. During this experiment, larvae were fed Isochrysis galbana (clone T-ISO). The larvae were grouped into four groups depending on origin of broodstock and the culture temperature. The growth rate was statistically higher in the group from Punta Arenas at 15 ºC, while settlement length was smaller in the group from Chiloé at 9 ºC. In both cases, the remaining groups did not differ significantly. Settlement survival showed no significant differences between populations and temperatures. Both populations showed a better use of accumulated thermal units (ºC day -1 ) during growth at 9 ºC than at 15 ºC. Despite the genetic differentiation of the Punta Arenas population, the productive outcome of M. chilensis larvae from broodstocks from different latitudes is similar.Key words: mussels, larvae, survival, growth, temperature. RESUMEN.Se obtuvieron larvas veliger D de reproductores de Mytilus chilensis procedentes de Punta Arenas y Chiloé (Chile), y se cultivaron a 9 ± 0.5 ºC y 15 ± 0.5 ºC para comparar los resultados del cultivo larvario de las dos poblaciones a dos temperaturas. Durante el experimento, las larvas fueron alimentadas con Isochrysis galbana (Clon T-ISO). Las larvas fueron cultivadas en cuatro grupos dependiendo del origen y la temperatura. La tasa de crecimiento fue estadísticamente mayor en el grupo de Punta Arenas a 15 ºC, y el tamaño de fijación fue menor en el grupo de Chiloé a 9 ºC. En ambos casos, los restantes grupos no presentaron diferencias significativas. La supervivencia hasta la fijación no presentó diferencias significativas entre poblaciones ni entre temperaturas. En ambas poblaciones se observó un mejor aprovechamiento de las unidades térmicas acumuladas (ºC día -1 ) en el crecimiento a 9 ºC que a 15 ºC. El resultado productivo de larvas de M. chilensis generadas por reproductores de distintas latitudes es similar, pese a la diferenciación genética de la población de Punta Arenas.