Acoustic remote sensing in marine environment for biological aims
- Autores: Salvatore Mazzola
- Directores de la Tesis: Cástor Guisande (dir. tes.)
- Lectura: En la Universidade de Vigo ( España ) en 2010
- Idioma: inglés
- Tribunal Calificador de la Tesis: Jesús García Lafuente (presid.), Gualtiero Basilone (secret.), Alberto M. Garcia García (voc.), Carlos Granado Lorencio (voc.)
- Materias:
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- Resumen
Most of the work carried out in the farmework of the present thesis concerns the use of acoustic devices and techniques to investigate marine envrironment and the biological resources sepcially the pelagic fish species as the case study of the European anchovy (Engrafulis encrasicolus L. 1758). Anchovy and sardine populations, have undergone large itnerannual fluctuation in total biomass, worldwide. Because of the short life span of these sepcies, the high variability in recruitment success determines rapid fluctuations in the population abundance. Many studies highlight the role of environmental conditions in determining recuitment succes of samall pelagic fish species, generally linging this success to survival of early life histoy stages, from larvae to juvenils. Serveral studies singles out the pmportance of wind stress in modulating mortality of early stages of pelagic pspecies. The sudden mortality modulating behaviour could be due to the actiosn of surface forcing, derived from the atmosferic energetc motions like wind stress and heat fluxes; these are the major causes of mixing of the upper layer sea. In this work the atmosphere acoustic remote sensig application to study the air seas exchages, was a new system developed and tested on board of a research vessel during oceanographic cursies. the on board SODAR system (MASD). The main underwater coustic applicaation for biological aims, in this thesis work concerned the use of a scientifica echosounder (SIMRAD EK 60) to study the abundance and distribution of the particles dispersed in the sqter column until the bottom (fish and ichthyoplankton). The general scope of the thesis work was to use acoustic data to collect physical and biological information in the marine environment, in order to asssess biological and environmental features and monitoring the fisherty production. Regardless the air sea interaction the main results showed that: instabilities produced by wind linke anchovy appear to be related to the wind mixing index; Among the analysed variables the air-sea heat fluxes, Sea Surface Temperature and, to a lesser exente, the wind induced turbulence , may be considered proxies of favourable anchovy spawing porducts. The SODAR system mounted on board of the research vessel may be useful to monitoring the dynamic meteorological-climatic processes of marine atmospher at mmico-and mesoscale .This system could be also used to study and evaluate the air-sea interactions, as much as studying relationship between air-sea fluxes, vertical wind structure and the mortality of eggs and larvae of small pelagic fish. Regaless the underwater acoustic the mai results supported by the results of the traditional sampling technique (plankton nets). it was observed that the standard echosounder used for the biomass evaluation of samll pelagic fish populations can bu successfully apllpied to study the botton conditions. The bottom analysis, in the Strait of Sicily, outlined a general preference of small pelagic fish schools for seabed of fines granuloetry and even relativiley small differences in sustrate type might provide different habitat conditions for fish species.
