Miguel Avendaño

Distribución temporal de larvas de Mytilus chilensis (Hupé, 1954) (Mollusca: Mytilidae), en el mar interior de Chiloé, sur de Chile

The larval presence of M. chilensis was determined monthly from September 2007 to March 2008, in Quillaipe, Metri, Sotomo, Canutillar, and Pichicolo (interior sea of Chiloe) using vertical plankton trawls through a water column from 0 to 7.5 m. At the same time, the reproductive stage of adult individuals was determined histologically. Larvae were detected continuously at the five study sites, with a significant increase from October to December, exceeding 49 thousand per m -3 at Canutillar where, along with Sotomo, the greatest densities were recorded during the study. Cohort analysis showed a similarity in the larval cohorts present at the different sites from September onwards; this was accentuated in November and December, as was the constant appearance of cohorts in the initial stages. In contrast with these results, the reproductive process of M. chilensis at these sites occurred from January to March. Whether or not the spawning recorded at these sites is responsible for the observed larvae is a matter of debate, as the sites may receive and retain larvae exported from other sites. These results suggest a need to compile further biological and ecological knowledge on the areas where this species is distributed and its larval and post-larval dynamics in order to identify exporting and retention areas and thereby contribute to efficient management and the optimization of spat collection.

Reestablecimiento de Choromytilus chorus (Molina, 1782) (Bivalvia: Mytilidae) en el norte de Chile

RESUMEN. Hasta fines del siglo pasado no existian registros de la presencia de Choromytilus chorus al norte de los 23°S, pese a antecedentes que senalaban su existencia en epocas pasadas. Ciertos cambios relacionados con las masas de agua costeras de esta zona, habrian generado la ausencia o escasez que presentaba el entorno costero actual. Sin embargo, hace una decada atras, su presencia en el norte de Chile, comienza a tener connotacion pesquera. En el presente trabajo se confirma su reestablecimiento en las regiones de Antofagasta y Tarapaca, mediante prospecciones realizadas en seis lugares donde se registro su presencia, asi como mediante la captacion de semilla en colectores suspendidos. Se indica interaccion con Aulacomya ater, a la cual ha desplazado a estratos mas profundos, mientras que su reestablecimiento, iniciado en las regiones de Atacama y Antofagasta, y que se amplio posteriormente a la region de Tarapaca; permite postular la hipotesis que la dinamica de estos bancos, responderia a una estructura de metapoblacion, dado el sistema de corrientes y vientos que predominan en la zona norte, permitiendo la adveccion larval de poblaciones existentes en la region de Coquimbo. Palabras clave: recolonizacion, Choromytilus chorus, norte de Chile, Pacifico suroriental. Reestablishment of Choromytilus chorus (Molina, 1782) (Bivalvia: Mytilidae) in northern Chile

Parámetros reproductivos y poblacionales de Thais chocolata (Duclos, 1832) (Gastropoda, Thaididae), en la reserva marina La Rinconada, Antofagasta, Chile

Reproductive and population parameters of Thais chocolata that would contribute to the validation of the current extraction standards were obtained by performing a study in the protected area of La Rinconada Marine Reserve, Antofagasta, Chile, from December 2008 to January 2010. In terms of reproduction, the results revealed asynchronic gonad development in the population, with specimens in different stages of maturity throughout the year. Mature individuals were distributed between 5 and 13 m depth, forming aggregations at 5 m depth during much of the year. Periods of greater maturity were observed from July to August and November to January, with the most important aggregations at the end of both periods. A relationship was observed between the months with the greatest maturity and aggregations and the months with the highest daily temperature fluctuations. At the population level, the results allowed us to estimate 2.3*10 6 individuals, with 39% of this population over the minimum legal size (55 mm). The relatively slow growth estimated for this population was probably influenced by the high variability of the bottom temperature in this area. The critical size and size at first maturity of the population were higher than the minimal legal size, making it is necessary to review the current fishing regulation for this species. The effectiveness of the State marine reserves in the conservation of this marine resource was demonstrated.