| Resumo: |
This dissertation is focused on the study of implications of spatial patterns on survival of eggs and larvae and subsequent recruitment of the SW Atlantic anchovy, Engraulis anchoita. The study of distribution patterns is encompassed within the conceptual framework of the analysis of reproductive strategies of marine bony fish, as adaptations that enable them to cope with and actively exploit environmental variability, regulating their abundance and avoiding extinction. The SW Atlantic anchovy, is ideally suitable for studies on reproductive biology and recruitment on a comparative basis. Its spawning and nursery grounds are located in very diverse ecosystems. This variety refers to their physico-chemical properties, carrying capacity, the influence of several water masses, and the contribution of fresh water runoffs from different origins. Important physical features are seasonal thermocline formation, and the presence of transitional regions such as oceanic, shelf-break and tidal shelf fronts, and upwelling areas. The aim of this dissertation was to study the biological response to that environmental heterogeneity. The central issue of the discussion was the implication of that apparent lack of association between reproductive activity and environmental conditions, on the rates of growth and mortality during the early developmental stages, and subsequent recruitment. As a working hypothesis the existence of some degree of dependence between those population attributes and the evolution of the distributional patterns during the early ontogeny was postulated. To prove this assumption distributions were studied not only in their usual connotation (i.e. spatial arrangement, geographic location), but also in their ecological and statistical sense, in a variety of time-space scales, from the Eulerian and Lagrangian perspectives. The final outcome, based on the identification of factors influencing the survival of the early developmental stages of the species, was the derivation of models that could describe mechanisms of demographic regulation.
Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales.
|
