Browsing by Author "Patricio Ojeda, F."

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    Genetic population structure in the Chilean jack mackerel, Trachurus murphyi (Nichols) across the South-eastern Pacific Ocean
    (2009) Cardenas, Leyla; Silva, Andrea X.; Magoulas, Antonios; Cabezas, Josefina; Poulin, Elie; Patricio Ojeda, F.
    The Chilean jack mackerel Trachurus murphyi, is a pelagic fish from the Carangidae family that is distributed in the South Pacific Ocean. Because this species constitutes an important economic resource across the South Pacific and plays an important ecological role in this ecosystem there is a growing interest in determining its population structure. In this study, we used molecular markets (mitochondrial DNA sequences and microsatellites) from Chilean jack mackerel samples to investigate its genetic population structure across the South Pacific Ocean. The mitochondrial DNA did not detect a genetic structure in T murphyi populations in the Pacific Ocean, but revealed very low haplotype diversity and a short genealogy history compared to other small-pelagic species. The same general pattern of a lack of genetic structure was found with microsatellite loci; however, a large genetic diversity was revealed with microsatellite markers. The present results did not support the existence of different stock units for T murphyi across the South Pacific Ocean but a more holistic approach will be necessary to determine an adequate management strategy for this fishery. (C) 2009 Elsevier B.V. All rights reserved.
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    Phytoplanktonic primary production modulated by coastal geomorphology in a highly dynamic environment of central Chile
    (2009) Palma, Alvaro T.; Henriquez, Luis A.; Patricio Ojeda, F.
    Coastal upwelling circulation has a regional fertilizing effect upon phytoplanktonic communities (i.e. enhancement of photosynthetic rates, increased biomass), but its influence at smaller spatial and temporal scales is less clear. At local scale (100's m) and under upwelling-favorable conditions, retention zones with higher primary production (PP) levels tend to occur at the lee or protected side of small headlands induced by the orientation, geometry, size and general geomorphology of these coastal formations. Here we quantified net and gross primary production (NPP and GPP), community respiration (CR) and biomass (Chl-a) of natural phytoplankton assemblages in coastal environments of central Chile. The main goal was to determine short-term patterns in PP and CR around two small peninsulas in central Chile where measurable differences in several environmental variables can be expected, and we hypothesize that differences will no longer occur under non-upwelling/relaxation conditions. Results indicate that NPP GPP and CR differ at local scale, and contrary to previous findings we found that weakening of upwelling-favorable winds can generate an opposite pattern to that observed under active upwelling periods, whereas the exposed site retains higher biomass and exhibits higher PP levels compared to the protected site. Our results highlight the importance of short-term variability in PP, CR and their coupling with the distribution and abundance of the quick-responding phytoplankton at local spatial scale.
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    The use of otoliths and larval abundance for studying the spatial ecology of the blenny Scartichthys viridis (Valenciennes, 1836) in coastal central Chile
    (2009) Hernandez-Miranda, Eduardo; Veas, Rodrigo; Valeria Espinoza, C.; Thorrold, Simon R.; Patricio Ojeda, F.
    Several studies in marine ecology have focused on evaluating what determines the spatial and temporal structure of organisms within the intertidal and coastal zone. Our results suggest that individuals of Scartichthys viridis, separated by spatial scales greater that 200 km, would also be demographically separated, having independent reproductive activity and population dynamics. Such spatial difference is suggested by analyzing trace elements found in the otoliths of recruited specimens, which were obtained simultaneously from Los Molles and Isla Negra, central Chile. Considering larval dispersion potential (92-106 days), based on daily micro increments of otoliths, both populations could be connected. However, this may not be the case, since the behavioral trend of these fish during larval stages seems to be near the areas where they hatched. Although this study does not fully reveal the specific biophysical mechanisms involved, it proposes some alternatives that may address such questions. These results may assist in guiding further studies towards explicitly determining population segregation at minor spatial scales, as well as the specific biophysical mechanisms that determine transport, larval dispersion and population connectivity of fishes in intertidal environments.