Mónica Fernández

Estudio preliminar de las comunidades bentónicas delos fondos de pesca de langostino patagónico del GolfoSan Jorge (Argentina)

Benthic sampling was carried out in the Patagonian shrimp (Pleoticus muelleri Bate, 1888) lishing grounds in San Jorge Gulf, Argentina, in order to determine composition, spatial distribution and relative abundance of the species in the benthic communities. Biological samples were taken with an epibenthic sledge in 66 sampling stations, and 57 sediment samples for granulometric analysis with a Picard dredge. A total of 135 taxa from the benthic communities were identified. Cluster analyses

Physico-chemical characterization of the benthic environment of the Golfo San Jorge, Argentina

The benthic system of the Golfo San Jorge was characterized from physico-chemical parameters based on samplings obtained during seasonal research cruises carried out on board the INIDEP vessels from springtime 1999 through wintertime 2000. Spatial and seasonal variations of temperature, salinity. density, oxygen content and chlorophyll-α in bottom water and concentration of total organic matter, total organic carbon, total nitrogen, chlorophyll-α and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The behaviour of the physico-chemical characteristics of the benthic habitat, studied applying statistical techniques, defined three sectors with particular characteristics and minimum seasonal variations: sector 1, the largest and deepest one, comprises the central area of the gulf and corresponds to a depositional environment; sector 2 comprises the areas next to the extremes of the gulf and corresponds to a flow or erosive environment; sector 3 includes the coastal area and south-east part of the gulf and belongs to a transitional environment.

Grain-size analysis of surficial sediments from Golfo San Jorge, Argentina

A detailed cartography of surficial sediments from Golfo San Jorge, Argentina is presented. Cluster analysis and principal components analysis (PCA) were applied considering the weight percentage of every granulometric fraction, carbonate concentration and the depth of 39 stations carried out during research cruises on board the RV ‘Captain Oca Balda’ (INIDEP).  The results defined three sectors: Sector 1, an area near the coast including Dos Bahias and Tres Puntas capes; Sector 2, a deep area far from the coast; and Sector 3, a coastal area and a south-east area between Tres Puntas cape and the inner area of the gulf. The first sector is characterized by the predominance of a coarse granulometric fraction and carbonate content. The second is defined by depth and presence of a fine granulometric fraction; while the third sector is considered a transitional sector, between the first and the second, dominated by fine sands. Sectors belong to environments of different kinds of energy or hydrodynamic conditions.

Caracterización físico-química del sistema bentónico en el sector sur del Golfo San Jorge, Argentina

Se presenta la caracterizacion fisico-quimica de los sedimentos superficiales y del agua de fondo del area sur del Golfo San Jorge, zona donde se localizan las mayores concentraciones de langostinos que sustentan la pesqueria del litoral patagonico. Los datos analizados provienen de la Campana de Investigacion OB-05/03 realizada en junio de 2003 con el BIP Capitan Oca Balda del INIDEP. Se analizaron las variables ambientales: temperatura, salinidad, densidad, contenido de oxigeno y de clorofila a del agua de fondo y fracciones granulometricas, concentracion de materia organica total, carbono organico total, nitrogeno total, fosforo total, clorofila a y feopigmentos en sedimentos, como asi tambien, profundidad. El origen y el valor nutricional de la materia organica sedimentada tambien fueron contemplados. Para el tratamiento numerico de los datos se aplico la tecnica de clasificacion. La distribucion espacial de las variables coincidio con la definicion de dos sectores en el area sur del Golfo San Jorge, correspondientes al Ambiente Deposicional (de condiciones hidrodinamicas bajas, depositacion de elementos granulometricos finos y abundante material organico en sedimentos) y al Ambiente Transicional (de condiciones hidrodinamicas medias, granulometria mediana y concentraciones moderadas de material organico en sedimentos), ambos previamente descritos por Fernandez et al. (2003, 2005, 2006). Esta investigacion esta orientada a caracterizar desde un punto de vista fisico-quimico el ambiente donde se registran las mayores concentraciones de este recurso pesquero, para un posterior analisis relacionado con los patrones de distribucion y abundancia del langostino, en el sector sur del Golfo San Jorge, dado que se advierte una relacion entre los indices de abundancia de la especie y algunas de las variables oceanograficas y sedimentologicas

New contribution on spatial and seasonal variability of environmental conditions of the Golfo San Jorge benthic system, Argentina

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll- a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll- a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments. Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.

Distribución espacial del langostino patagónico (Pleoticus muelleri, (Bate, 1888)) y su relación con las variables ambientales, Golfo San Jorge, Argentina

The analysis of the distribution of shrimp concentrations in the south of the San Jorge Gulf is presented, as well as their relationship with the physico-chemical characteristics of the superficial sediments and the bottom water. Data analyzed were obtained from the Shrimp Project Research Cruise OB-05/03 carried out during June 2003. Biological variables analyzed were: juvenile, subadult and adult shrimp densities and size structure. Correspondence analyses were applied for numerical data treatment. The distribution of the different shrimp categories in the studied area shows a west-eastern pattern, being the juveniles towards the west coast and the adults larger than 41 mm carapace length towards the northeast, while the main concentrations of subadults and adults were found in the rest of the study area. A relationship between the spatial distribution of the juvenile and adult categories and depth and total organic carbon (TOC) was determined. The highest adult densities (> 41 mm carcass length) were related with the highest depths and the lowest values of TOC. While the highest juvenile densities were related with the lowest depths and the highest TOC concentrations.

Diet of the red shrimp Pleoticus muelleri (Bate, 1888) in Patagonian fishing grounds, Argentine

Se analizo el contenido estomacal de 2.157 langostinos Pleoticus muelleri de los fondos de pesca patagonicos, en Argentina. Las muestras provinieron de 40 lances realizados durante una campana de investigacion del BIP Capitan Oca Balda, del INIDEP (junio, 2003) y de los buques comerciales Arbumasa XVI (mayo 2003) y Arbumasa XV (julio 2003), entre los 43°S y 47°S. El objetivo de este trabajo fue determinar la vinculacion entre la composicion de la dieta del langostino y las comunidades bentonicas de los fondos de pesca. Asimismo se considero la relacion entre la dieta y la talla. La ocurrencia de los items alimentarios alcanzo el 94% de los estomagos de P. muelleri con diferentes grados de replecion. Los items alimentarios correspondieron a diez taxa. Crustaceos, poliquetos y moluscos fueron los items mas importante y abundantes, estando representados en un 100% de los estomagos. La diversidad trofica (H?; indice de Shannon-Wiener), presento valores entre 1,45 y 2,48; el 60% de los valores fue superior a 2. La uniformidad dietaria (J?; indice de Pielou) presento valores que indicaron una buena y variada disponibilidad de alimento, consecuencia de la composicion y estructura de la comunidad bentonica de los fondos. La dieta de P. muelleri consistio predominantemente en tres categorias de organismos de fondo: 1) demersales (miscidaceos, eufausidos, decapodos), 2) epifaunales (anfipodos, isopodos, cumaceos, gasteropodos) y 3) infaunales (bivalvos, poliquetos, foraminiferos, nematodos). Se concluye que P. muelleri es un depredador importante sobre organismos bentonicos.

Analysis of the relationship between relative abundance of mature, impregnated females of Pleoticus muelleri (Bate, 1888) (Crustacea, Decapoda) and environmental variables through statistical models

The relationship between the relative abundance of mature and impregnated females of the Ar- gentine red shrimp Pleoticus muelleri (Bate 1888) and environmental variables was analyzed using statistical methods. Analyzed data came from the research cruises of the Instituto Nacional de Investigacion y Desarrollo Pesquero (INIDEP) carried out during January 2000, 2001, 2005, and 2007; March 2006; and November 2004, 2005, and 2006 in San Jorge Gulf (Argentina). The biological variables considered were the relative abun- dances of mature and impregnated female shrimp, whereas the environmental variables corresponded to depth, bottom water temperature and salinity, and the difference between surface and bottom water temperature and salinity. Generalized additive models were used as an exploratory tool for the numerical data and the general linear models as a confirmatory tool. The results showed that the distributions and abundances of mature and impregnated females were related to the bottom water temperature and salinity and to depth. The relationship increased along with temperature; with salinity, however, it decreased for mature females and increased for impregnated females. An optimal depth range was evidenced, where the largest concentrations of these indi- viduals were located.