Resumen.-Los fiordos de la Patagonia chilena, se caracterizan por fuertes gradientes físico-químicos horizontales y verticales que ejercen consecuencias en la distribución y abundancia del ictioplancton. Se recolectaron muestras de plancton mediante arrastre oblicuo con una red bongo en 40 estaciones, a bordo de un crucero bio-oceanográfico en fiordos interiores de la XI región sur de Chile (47° a 51°S). Los datos ambientales de la columna de agua fueron obtenidos mediante un perfilador de conductividad-temperatura-profundidad (CTD), y la turbidez fue medida con un turbidímetro portátil entre 0 y 100 m de profundidad. Las estaciones se distribuyeron por zona oceánica, canales y área de influencia de agua dulce. Se recolectó un total de 1424 larvas, representando 21 familias y 41 taxa. Los taxa dominantes fueron Maurolicus parvipinnis (31%), Sebastes oculatus (12%), Merluccius australis (11%), Lampanyctodes hectoris (10%) y Bathylagichthys parini (8%). La mayor variabilidad ambiental fue dada por la salinidad, principalmente en la zona con descarga de agua dulce. La zona oceánica presento una columna de agua mezclada con la mayor presencia de mictófidos como L. hectoris y peces hacha M. parvipinnis. No hubo un efecto significativo de los gradientes de turbidez sobre los ensambles de larvas de peces durante primavera. La zona de los canales se aprecia una mayor estratificación de la salinidad, densidad y una disminución de la turbidez, donde se distribuyeron en general las especies con menores abundancias. Por lo tanto, es posible definir dos ensambles ictioplanctónicos, uno con influencia oceánica y el otro de canales y zonas interiores.Abstract.-Chilean Patagonian fjords are characterized by strong stratification and chemical gradients which influence the ichthyoplankton distribution and abundance. Plankton samples were collected through bongo net oblique tows in 40 stations from onboard a bio-oceanographic cruise took place in inner fjords of southern Chile (47° to 51°S). Water column physical data were obtained with a conductivity-temperature-depth profiler (CTD) and turbidity was measured with a portable turbidimeter from 0 to 100 m depth. Stations were distributed by three zones: oceanic, channels and continental waters. A total of 1424 larvae were collected, representing 21 families. Dominant taxa were Maurolicus parvipinnis (31%), Sebastes oculatus (12%), Merluccius australis (11%), Lampanyctodes hectoris (10%), and Bathylagichthys parini (8%). Most of the environmental variability was determined by salinity, mainly in the area where continental waters are discharged. The water column in the oceanic zone presented mixed waters dominated by the myctophid L. hectoris and the sternoptychid M. parvipinnis. No significant effect of turbidity gradients on larval fish assemblages was evident during spring. The channel zone was both more saline, and density stratified with less turbidity, and lower abundance of species. Two ichthyoplanktonic assemblages were evident, one living in oceanic waters, and the other from...
Abstract.-Larval size is considered as an important variable to understand the changes in larval development and identification of a suitable environment for larval growth and survivor. Larvae of the Pacific mackerel (Scomber japonicus) have a slow growth during the early stages of development (6-8 mm SL); subsequently, the growth rate increases, but the development depends mainly on the temperature and food. The aim of this study was to identify the areas and seasons favorable for larval development of S. japonicus, in relation to the sea surface temperature and the zooplankton biomass, off the west coast of the Baja California Peninsula (~25°-32°N) from 2006 to 2010. Larvae of the Pacific mackerel showed the greatest amplitude in their spatial distribution during spring, but with greater restricted abundance compared to Punta Eugenia (~28°N) during summer. Changes in its distribution were influenced by geostrophic flow and thermal variability. Linear regression analysis allowed to identify areas favorable for larvae development, with a lower development in spring, related to a narrow range of temperatures and levels of comparatively low zooplankton biomass. In contrast, during summer the largest increase in body height () was related to a wide range of temperatures, while its low variability (standard error) coincided with high levels of zooplankton biomass. It is considered that thermal conditions and food availability, favor an optimum larval development, particularly during the summer season.Key words: Pacific mackerel, fish larvae, isometric growth, suitable areas, California CurrentResumen.-El tamaño larval es una variable importante para entender los cambios en el desarrollo y la identificación de un entorno adecuado para el crecimiento y la supervivencia larval. Las larvas de la macarela del Pacífico (Scomber japonicus) presentan un lento crecimiento durante las primeras fases del desarrollo (6-8 mm de LE); posteriormente, la velocidad de crecimiento aumenta, pero el desarrollo depende principalmente de la temperatura y del alimento. El objetivo del presente trabajo fue identificar las zonas y temporadas propicias para el desarrollo larval de S. japonicus, en relación a la temperatura superficial del mar y la biomasa del zooplancton, frente a la costa occidental de la Península de Baja California (~25-32°N) del 2006 al 2010. Las larvas de la macarela del Pacífico mostraron la mayor amplitud en su distribución espacial en primavera, pero con mayor abundancia restringida frente a Punta Eugenia (~28°N) durante el verano. Los cambios en su distribución, estuvieron bajo la influencia del flujo geostrófico y la variabilidad térmica. El análisis de regresión lineal permitió identificar zonas propicias para el desarrollo de larvas, con un menor desarrollo en primavera, relacionado con un int ervalo estrecho de temperaturas y niveles de biomasas del zooplancton comparativamente bajos. En contraste, durante el verano el mayor incremento en la altura del cuerpo () fue relacionado con un amplio intervalo de tempe...
Pacific chub mackerel (Scomber japonicus) is a relevant fishery resource shared among three countries in the northeastern Pacific. The spatiotemporal distribution of larvae has been related to the convergence of oceanographic mesoscale structures, which can generate considerable variability in the morphology of fish larvae. The main goal of this work was to describe the shape changes of larval S. japonicus and their relationship with oceanographic variability, through geometric morphometric analysis to assess the seasonal variability of 10 homologous landmarks distributed on the pre‐anal section of 331 larvae from off the western coast of the Baja California Peninsula (WCBCP), Mexico (2006–2008). The results showed two principal morphotypes in Pacific chub mackerel larvae: The first morphotype had a more hydrodynamic body (longer and shallower head), influenced by increased sea surface flow and colder sea surface temperatures mainly during spring, and the second morphotype had robust larvae (shorter and deeper head) under slower current flow and warmer sea surface temperatures during winter and summer. We concluded that changes in larval body shape are influenced mainly by sea surface flow and sea temperatures, probably associated with the ability to reach higher swimming speeds during feeding success.
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