Browsing by Author "Ospina-Alvarez, Andres"

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    Electronic Tagging of Atlantic Bluefin Tuna (Thunnus thynnus, L.) Reveals Habitat Use and Behaviors in the Mediterranean Sea
    (2015) Cermeno, Pablo; Quilez-Badia, Gemma; Ospina-Alvarez, Andres; Sainz-Trapaga, Susana; Boustany, Andre M.; Seitz, Andy C.; Tudela, Sergi; Block, Barbara A.
    We analyzed the movements of Atlantic tuna (Thunnus thynnus L.) in the Mediterranean Sea using data from 2 archival tags and 37 pop-up satellite archival tags (PAT). Bluefin tuna ranging in size from 12 to 248 kg were tagged on board recreational boats in the western Mediterranean and the Adriatic Sea between May and September during two different periods (2000 to 2001 and 2008 to 2012). Although tuna migrations between the Mediterranean Sea and the Atlantic Ocean have been well reported, our results indicate that part of the bluefin tuna population remains in the Mediterranean basin for much of the year, revealing a more complex population structure. In this study we demonstrate links between the western Mediterranean, the Adriatic and the Gulf of Sidra (Libya) using over 4336 recorded days of location and behavior data from tagged bluefin tuna with a maximum track length of 394 days. We described the oceanographic preferences and horizontal behaviors during the spawning season for 4 adult bluefin tuna. We also analyzed the time series data that reveals the vertical behavior of one pop-up satellite tag recovered, which was attached to a 43.9 kg tuna. This fish displayed a unique diving pattern within 16 days of the spawning season, suggesting a use of the thermocline as a thermoregulatory mechanism compatible with spawning. The results obtained hereby confirm that the Mediterranean is clearly an important habitat for this species, not only as spawning ground, but also as an overwintering foraging ground.
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    Environmental and demographic factors influence the spatial genetic structure of an intertidal barnacle in central-northern Chile
    (2019) Barahona, Mario; Broitman, Bernardo R.; Faugeron, Sylvain; Jaugeon, Lucie; Ospina-Alvarez, Andres; Veliz, David; Navarrete, Sergio A.
    Understanding the multiplicity of processes producing genetic patterns in natural populations can shed light on the ecology and evolution of species, and help guide effective management and conservation strategies. Here we investigated the role of environmental, demographic, and geographic factors in shaping the spatial patterns of genetic diversity and differentiation of the intertidal barnacle Notochthamalus scabrosus along the central-northern coast of Chile (28-34 degrees S). We analyzed genetic data from 7 microsatellite loci genotyped for 300 individuals sampled from 10 sites and combined this information with 8 site-specific environmental (4), demographic (2), and geographic (2) variables using least squares linear regressions, generalized linear models, and matrix regression analyses. We found a strong association between the spatially structured genetic diversity of N. scabrosus and patterns of temporal variability in chlorophyll a, and among-site differences in seawater temperature and adult abundance. Our results illustrate that population size, partly driven by recruitment success, can leave a signal on genetic structure of this highly dispersive marine species. The significant effect of temperature and chlorophyll a stresses that local adaptation may be key to understanding the spatial genetic structure of our model species. Hence, the results of this work represent an advance towards understanding the usually complex causal relationships between environmental variables, gene flow, and genetic diversity patterns of coastal populations.
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    Influence of larval traits on dispersal and connectivity patterns of two exploited marine invertebrates in central Chile
    (2019) Blanco, Marta; Ospina-Alvarez, Andres; Navarrete, Sergio A.; Fernandez, Miriam
    Environmental variability can influence larval development rates and affect critical processes in the dynamics of natural populations, such as dispersal distances and connectivity, when modulated by different larval traits. Knowledge of connectivity patterns in marine populations is fundamental for defining population viability and progressing with management and conservation goals. Here, we developed a biophysical, individual-based larval dispersal model to assess the effect of oceanographic variability and biological traits (i.e. larval diel vertical migration [DVM] and temperature-dependent larval development [PLD]) on recruitment success, dispersal distance, and alongshore connectivity patterns. We selected 2 species exploited by Chilean artisanal fisheries: Loxechinus albus (PLD: 20 d) and Fissurella latimarginata (PLD: 5 d). A sensitivity analysis was used to examine the effect of intrinsic (DVM and PLD) and extrinsic (release depth, latitude, and timing) processes. Release location and timing of release explained respectively 24.30 and 5.54% (F. latimarginata) and 34.8 and 4.19% (L. albus) of the variability observed in recruitment success, and 23.80 and 6.94% (F. latimarginata) and 26.10 and 19.60% (L. albus) of the variability observed in dispersal distance. Most recruitment to local populations was allochthonous, presenting low levels of self-recruitment and local retention, including species with short PLD. Similar geographic patterns of source and destination strengths were observed in both species, showing a geographic mosaic of source and sink populations with relatively higher importance towards the northern region of the study area. Our findings allow us to identify primary determinants of recruitment success and dispersal distance for 2 important exploited species in Chile.
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    Multidimensional data analysis to guide the sustainability of a small-scale fishery affected by poaching
    (2022) de Juan, Silvia; Subida, Maria Dulce; Ospina-Alvarez, Andres; Aguilar, Ainara; Fernandez, Miriam
    The substantial increase in poaching within the fisheries' management areas (MA) system in central Chile is likely driven by an interplay of socio-economic factors. To assess this problem, the exploitation state of an important benthic resource in the MAs (i.e., keyhole limpet) was related to socio-economic drivers of the fishery. The potential drivers of poaching included the level of formal and informal enforcement and distance to sur-veillance authorities, a rebound effect of fishing effort displacement by MAs, wave exposure and land-based access to the MA, and alternative economic activities in the fishing village. A Bayesian-Belief Network approach was adopted to assess the effects of potential drivers of poaching on the exploitation state of limpets, assessed by the proportion of the catch that is below the minimum legal size and by the relative median size of limpets fished within the MAs in comparison with neighboring open access areas. Results showed the important role of socio-economic (e.g., alternative economic activities in the village) and context variables (e.g., fishing effort displacement or distance to surveillance authorities) as drivers of poaching in the study area. Scenario analysis explored variables that are susceptible to be managed, evidencing that an integrative ecological and socio-economic approach can offer solutions to the unsustainable exploitation of marine resources.