http://hdl.handle.net/1834/1339 Mon, 06 Feb 2012 15:19:40 GMT 2012-02-06T15:19:40Z http://www.oceandocs.org:80/retrieve/4173/Argentine-ss.jpg http://hdl.handle.net/1834/1339 http://hdl.handle.net/1834/3548 Title: Análisis espacio-temporal del estado nutricional de larvas de anchoíta Engraulis anchoita. Relación con las características hidrográficas y la disponibilidad de alimento Authors: Díaz, M.V. Abstract: Nutritional condition studies allow the assessment of physiological state of each larva and thus, the establishment of favourable nursery areas which provide better survival and growth. In the present work, morphometrical, histological and biochemical techniques were employed to assess nutritional condition of anchovy, Engraulis anchoita, larvae captured in the Argentine Sea. Its results were complemented with oceanographic data and information about zooplankton abundances, both prey and predators of anchovy larvae. Anchovy larvae abundance and distribution would be mainly determined by physico-chemical variables. Even though no significant differences were found in larval nutritional condition among the studied areas, larval condition was slightly better in frontal areas characterized by mixed water masses. On the other hand, anchovy larvae condition seems to be favoured during seasons when larval abundances remain low. Probably, ocean conditions are almost always favourable for larval growth and survival during the whole year, but low or intermediate larval densities allow avoiding both intra and inter-specific competition. As only a small number of anchovy larvae were described as in starving condition, it can be assumed that E. anchoita, finds environmental conditions that favour its growth and survival. during all seasons in the studied area. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/1834/3548 2010-01-01T00:00:00Z http://hdl.handle.net/1834/3877 Title: Modelado numérico del ecosistema de los golfos norpatagónicos Authors: Tonini, M.H. Abstract: This dissertation analyses the oceanic circulation of the Norpatagonian Gulfs, a region of the Argentinean Sea that has long been recognized for the high productivity and biodiversity of the ecosystem. The study aims towards a systematic exploration of the physical processes that control the circulation using a high resolution three dimensional numerical model. To facilitate the dynamical understanding of the results our experimental strategy was to start with a constant density (barotropic) model forced by tides and winds, and to progress to a more complex case including density stratification generated by surface fluxes of heat and humidity. The main result that stems from the numerical experiments is that tidal forcing significantly contributes to the overall subtidal residual circulation both in the homogenous and stratified models. The barotropic model shows that the nonlinear interaction between the oscilating tide and bottom topography leads to the formation of several robust residual circulation patterns: basin gyres, bathymetric vortices and coastline cuadrupoles, whichs are formed by recirculating eddies at mouths of SJG and GN. With the exception of the winter months, when the winds are stronger, the barotropic ocean response is completely dominated by the cyclonic tidal residual. It is necessary to have a strong wind in the northerly or westerly direction to break that pattern. The results of the stratified model also shows the profound influence of the tides in shaping the annual cycle of the circulation inside San Matias Gulf. The overall circulation pattern is dominated by a strong cyclonic gyre (composed by two recirculating sub-gyres) during summer with smaller anticyclonic gyres on the southwest coast and north of Valdes Peninsula. The spinup of the cyclonic circulation between October and February is caused by the interaction of the tides and stratification (generated by surface heat fluxes) in the presence of variable topography. As a result of this closed circulation the Gulf is almost isolated from the shelf during summer. From March to September the stratification is eroded and the northern subgyre spins down and gradually shrinks in size being absorbed by the southern subgyre. Simultaneously, the western sector of the Gulf is occupied by an anticyclonic gyre. The inclusion of wind forcing does not substantially modified the structure and intensity of the summer gyres but strengthens both the cyclonic and anticyclonic circulation during fall-winter. There is a similar oceanic response in Nuevo Gulf, but in this case there is only one year-round cyclonic gyre that intensifies in summer and is reduced in spatial extension in winter with the appearence of a weak anticyclonic gyre in the western coast. The residual currents are dominated by a strong year-round dipole in San Jose Gulf. Being initialized with horizontally constant density, the model is also able to capture the oberved structure and intensity of main thermal fronts in the outer shelf and inside San Matias Gulf Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/1834/3877 2010-01-01T00:00:00Z http://hdl.handle.net/1834/4066 Title: Ensilado biológico de carpa común (Cyprinus carpio). Obtención, caracterización físico-química y microbiológica Authors: Sesto, A. Abstract: El objetivo del presente trabajo fue elaborar ensilados biológicos a partir de residuos de carpa común (Cyprinus carpio), utilizando dos fuentes de hidratos de carbono (miel y azúcar). Se realizaron dos formulaciones compuestas por: residuos de carpa, yogur (10%), azúcar (10%) o miel (10%) y ácido sórbico (0,25%). Se evaluaron los cambios durante el almacenamiento a 35-45° C. En la materia prima y en los ensilados se analizó: proteína bruta, extracto etéreo, humedad, cenizas, histamina, oxidación lipídica y bases nitrogenadas volátiles totales. Se determinaron mesófilos, coliformes totales y fecales, mohos, levaduras, Salmonella spp y bacterias ácido lácticas. Los parámetros evaluados en el análisis sensorial fueron color, consistencia y olor. En la materia prima el contenido proteico fue 13,92%, el extracto etéreo 1,43%, humedad 78,48% y cenizas 4,63%. En los ensilados, a los 30 días, el contenido proteico fue de 13,74% (azúcar) y 13,02% (miel), extracto etéreo 2,08% (azúcar) y 2,16% (miel), humedad 72,67% (azúcar) y 76,25% (miel) y cenizas 3,84% (azúcar) y 3,01% (miel). En todas las determinaciones de histamina se obtuvieron resultados negativos. El valor del ácido tiobarbiturico fue incrementándose hasta llegar a valores de 2,79 mgMDA/kg (azúcar) y 2,88 mgMDA/kg (miel). El nitrógeno básico volátil total, en ambos ensilados alcanzó valores cercanos a 97 mg/100g. El valor de pH a las 24 hs fue de 4,7, alcanzando valores hacia el octavo día de 4,2. Los nulos o bajos recuentos microbiológicos demuestran una óptima calidad de la materia prima y de los ensilados. Las características sensoriales fueron similares en ambas formulaciones. La tecnología de elaboración de ensilados biológicos nos permite utilizar los residuos generados del procesamiento de la carpa incluyendo miel o azúcar como fuentes de carbohidratos, recuperando los componentes de alto valor nutricional presentes en los mismos y contribuyendo al mismo tiempo con la disminución de la contaminación ambiental. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/1834/4066 2010-01-01T00:00:00Z http://hdl.handle.net/1834/3585 Title: Estudio de edad y crecimiento de la raya hocicuda Dipturus chilensis (Guichenot,1848) en el Atlántico Sudoccidental (34º -55º LS y 52º -69º LW) Authors: Zavatteri, A. Abstract: This paper deals with the age and growth parameters of the Southwest Atlantic beaked skate Dipturus chilensis, as well as with some reproductive features of the species. Samples of individuals inhabiting 34°-55°S and 52°- 69°W were analyzed. They were taken during surveys carried out by the National Institute for Fisheries Research and Development (INIDEP) research vessels, as well as by a landing sampling at Mar del Plata port. The fish age was determined by counting growth rings from thin sections of the vertebral centra of 414 fish ranging 24-110 cm (203 males) and 24-115 cm (211 females) total length. The vertebral sections were stained using cobalt hloride. Both average per cent error (APE=5.94) and precision (D=5.89) indexes suggested that the method used for estimating age in D. chilensis was precise enough. The marginal increment analysis (MIA) supported the hypothesis of an annual deposition of a pair of bands, which ended during the autumn months. The maximum ages observed in males and females were 21 and 25 years, respectively. After fitting the von Bertalanffy and the Gompertz growth models, the last one appeared to be the most appropriated to describe the growth of the species, whose parameters were estimated to be: L =114.32 cm; k=0.10 years-1; t0=4.95 years (males), and L = 149.05 cm; k=0.07 years1; t0=-8.11 years (females). The asymptotic length estimates of both males and females were closer to the observed values than those derived from the von Bertalanffy model. Growth differences between sexes were significant, the females reaching a larger size than males. On the basis of macroscopic examinations of the gonad development, age and length at 50% maturity were estimated to be 94.04 cm and 17.7 years (females) and 84.04 cm and 14.6 (males). These results indicate that D. chilensis is a long-living, slow growing and delayed maturating species, and therefore it is particularly vulnerable to suffer overexploitation if facing heavy fishing pressure. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/1834/3585 2010-01-01T00:00:00Z