Examinando por Autor "Castillo Silva, Manuel"

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    Growth and mortality of larval anchoveta Engraulis ringens, in northern Chile during winter and their relationship with coastal hydrographic conditions
    (Fisheries Oceanography, 2017) Conteras Herrera, Jorge; Rodriguez Valentino, Camilo; Landaeta Díaz, Mauricio; Plaza, Guido; Castillo Silva, Manuel; Alvarado Niño, Mónica
    Larval growth, age, growth effect and instantaneous mortality were estimated in anchoveta, Engraulis ringens, collected biweekly during the austral winter of 2014 in nearshore waters off Bay of Antofagasta (23°41′W–70°30′S), northern Chile. Through measuring standard length (SL) and sagitta microstructure analysis, it was estimated that the growth rate of E. ringens larvae decreased from June (0.85 mm day−1) to August (0.50 mm day−1). However, the water temperature was homogeneous during the sampling dates (14.6, 15.2, 14.4, and 14.6°C), suggesting that the decelerating larval growth was not linked to changes in sea temperature. Additionally, larvae with slow growth have larger otoliths compared with conspecifics with fast growth (growth effect). Larval mortality rates tended to decrease until the middle of July (0.18 per day) but increased to 0.25 per day in early August, which coincided with lower food availability (i.e., chlorophyll-a, 2.7–5.6 mg m−3) and a high occurrence of smaller larvae (1.58–11.5 mm). Partial least squares analysis indicates low covariance between the biological and oceanographic variables (PLS: 11.71%), suggesting that other factors, such as parental effects, may explain the abrupt decrease in the larval growth rates.
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    Influence of coastal oceanography on early life history traits of larval Patagonian sprat, Sprattus fuegensis along southeastern Pacific Ocean
    (Fisheries Oceanography, 2024) López Soto, Erika; Ord, Gillian K.; Castillo Silva, Manuel; Plaza, Guido; Cáceres Muñoz, Mario; González, María Teresa; Sepúlveda, Maritza; Guerrero, Alicia; Piñones, Andrea; Landaeta Díaz, Mauricio
    Early life history traits of small pelagic fish are usually affected by environmental conditions. Patagonian sprat, Sprattus fuegensis, is a small pelagic fish that inhabits the continental shelf, fjords and channels of Patagonia. Their larvae are usually exposed to large variations in physical and biological conditions. We evaluated the effects of environmental conditions on early life history traits of this key species encompassing over 20 years of information. The characterization of oceanographic features, larval abundance and distribution was carried out in western Patagonia between 1996 and 2019, while the growth and mortality rates were estimated for the austral spring 2019 between 49°54′S and 53°55′S. Larval abundance decreased three to ten times from 1996 to 1997 to the rest of the study period (2008–2010 and 2014–2019), with larger abundances being found over the shelf. In spring 2019, the growth rate was 0.20 ± 0.05 mm d−1 for larvae between 9 and 19 days after hatching. The growth rate was similar in partially stratified (7–50 J m−3) and stratified waters (50–100 J m−3), but slower in mixed waters (< 7 J m−3). GAM modelling showed that the faster larval growth occurred in partially stratified waters with temperatures above 7.5°C. Natural mortality rates were higher in partially stratified waters (24% of daily loss), lower in stratified areas (14%) and the lowest in the mixed water column (12%). Accordingly, larvae living in channels had faster growth rates but higher daily mortality, while those that hatched or were advected to water parcels on the continental shelf had slower growth but lower daily mortality. Finally, these latter traits may be an example of an inverse growth-selective survival strategy.
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    Turbulent Mixing in Patagonian Fjords and Channels
    (EGUsphere. Preprint repository, 2025) Rojas Celis, Marcela; Castillo Silva, Manuel; Pérez Santos, Iván; Barrios Guzmán, Carmen; Garcés Vergara, José; Guerrero, Alicia; Landaeta Díaz, Mauricio; Piñones, Andrea; Sepúlveda, Maritza
    The fjords and channels of Chilean Patagonia form a complex estuarine system where freshwater input, tidal currents, and stratification interact to modulate vertical mixing. We combined velocity microstructure profiles (VMP-250) and CTD-SRDL observations collected between 2023 and 2025 to quantify turbulent kinetic energy dissipation (ε) and vertical diffusivity (Kshear) across northern (42–46°S) and southern (52–55°S) Chilean Patagonia. Dissipation rates spanned 10⁻⁹–10⁻⁵ W kg-2 with maxima near sills and narrow passages such as Paso Desertores, where semidiurnal tides dominate energy input. Northern Patagonia exhibited seasonal stratification driven by freshwater inputs, while southern Patagonia remained weakly stratified and vertically well mixed throughout the year, aided by strong tidal currents and westerly winds. The tidal mixing parameter h/U³ indicated that semidiurnal tides account for ~97% of energy dissipation in the north and ~77% in the south. These findings highlight the strong spatial heterogeneity of turbulent mixing in Patagonian fjords and the key role of the interaction between tidal forcing and stratification in controlling vertical exchange. The results provide a framework for understanding how fjord systems may respond to changing freshwater inputs and atmospheric forcing under a warming climate.
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    When the fjords take a breath: Influence of wind forcing and Ekman dynamics on deep ventilation in the North Patagonian fjords
    (EGUsphere. Preprint repository, 2026) Sola Hidalgo, Camila; Pérez Santos, Iván; Castillo Silva, Manuel; Cornejo Marcela; Baldrich, Ángela; Castillo Álvarez, Maibelin
    Climate change directly alters the dissolved oxygen (DO) dynamics in the ocean. Ocean ventilation is critical for redistributing nutrients and gases throughout the water column, supporting essential biogeochemical cycles, and regulating the ocean capacity to absorb carbon dioxide and heat, making it essential for climate regulation. In the northern Patagonian fjords, ventilation events mitigate the impacts of deoxygenation and hypoxia, which are primarily driven by the poleward transport of Equatorial Subsurface Water. However, climate-driven changes such as surface warming and increased stratification may reduce the frequency and intensity of these ventilation events, thereby contributing to long-term deoxygenation. In this study, we examined the physical drivers, frequency, and variability of deep ventilation events in the northern Patagonian fjords from 2016 to 2024. ERA5 reanalysis data, from an oceanographic platform moored at 170 m depth, were used to evaluate wind stress, Ekman transport, pumping, and layer depth, alongside in situ time series of temperature, salinity, density, and DO. The results showed a seasonal increase in DO concentrations, classified as ventilation periods, whereas synoptic-scale oxygen events were identified and quantified as ventilation pulses. In total, 16 ventilation periods and 35 pulses were registered over the time series. Onshore Ekman transport favouring downwelling was identified as the main driver of ventilation periods from the austral winter to spring, accompanied by salinity decreases before and during oxygen increases. Pulses coincided with synoptic events dominated by negative total Ekman transport, driven by northern wind stress, along with concurrent thermohaline changes. Overall, these findings provide novel insights into the mechanisms governing oxygen renewal in the Patagonian fjords and underscore the importance of sustained observation systems in a changing ocean.