Browsing by Author "Hernandez-Miranda, Eduardo"

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    Inter-annual variability in somatic growth rates and mortality of coastal fishes off central Chile
    (2006) Hernandez-Miranda, Eduardo; Ojeda, F. Patricio
    The effects of El Nino (EN) and La Nina (LN) events upon marine organisms inhabiting the Eastern Pacific coast have been widely studied in recent years, concentrating primarily on changes in species composition and on population size. In this study, using somatic growth rates as metabolic response variables, we evaluated the mortality rates of coastal fishes inhabiting a central Chilean upwelling marine ecosystem in the South Pacific between 1990 and 2003. Four coastal fish species belonging to different trophic levels (one herbivore, one omnivore, and two carnivores) were analyzed. In all species, the estimated cohort somatic growth rates were low for those recruited during EN and high for those recruited during LN events. Annual cohort mortality rates were highest during EN events and lower during LN and transitional years. We propose that productivity (as a bottom-up driver) acts as a primary exogenous factor upon annual cohort mortality rates. We also propose that a plausible mechanism underlying this process is the negative effect the low somatic growth rates may have on fish ecological attributes such as their competitive abilities, condition factors, and predation risks, which ultimately may affect their fitness.
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    Temporal and spatial dissimilarities in an intertidal fish assemblage in the South Pacific Ocean: The role of the ENSO process and intrinsic habitat conditions in emerging patterns
    (2023) Espinoza, C. Valeria; Hernandez-Miranda, Eduardo; Gilabert, Horacio; Ojeda, F. Patricio
    An intertidal fish assemblage was studied in central Chile for 15 years in three localities: Isla Negra, El Tabo, and Las Cruces. Analyses of their multivariate dissimilarities were carried out considering temporal and spatial factors. Temporal factors included intra-annual and year-to-year variability. Spatial factors included locality, intertidal tidepool height, and each tidepool considered as a unique unit. Complementary to this, we tested the hypothesis that the El Nino Southern Oscillation (ENSO) would help explain year-to-year dissimilarities in the multivariate structure of this fish assemblage for the 15 years of data. To this end, the ENSO was regarded as a continuous inter-annual process as well as a set of discrete events. Additionally, dissimilarities in the temporal dynamics of the fish assemblage were evaluated considering each locality and tidepool unique units. Results indicated the following: (i) The most representative species for the whole area and period of the study were Scartichthys viridis (44 %), Helcogrammoides chilensis (17 %), Girella laevifrons (10 %), Graus nigra (7 %), Auchenionchus microcirrhis (5 %), and Helcogrammoides cunninghami (4 %); (ii) there is intra-annual (i.e., seasonality) and year-to-year multivariate variability in fish assemblage dissimilarities throughout the entire area of study, including all the tidepools and localities; (iii) when considering the spatial factor specifically, each tidepool unit, as well as their heights and localities, presented their own unique temporal yearto-year dynamics. The latter can be explained by the ENSO factor, also considering the intensity of the El Nino and La Nina events. In summary, the multivariate structure of the intertidal fish assemblage was statistically dissimilar when
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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.