Revista de Biología Marina y Oceanografía 44(2): 497-510, agosto de 2009 Distribución de merluza (Merluccius hubbsi Marini, 1933) en el Mar Argentino (41°-48°S) en relación con parámetros oceanográficos durante el invierno (1996-2003)Distribution of the Argentine hake (Merluccius hubbsi Marini, 1933) in the Argentine Sea (41º-48ºS) in relation to oceanographic parameters during winter (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) Abstract.-Salinity and temperature data recorded during 1996-2003 within the distribution area of the Patagonian stock of Argentine hake Merluccius hubbsi were analysed. These oceanographic variables were then related to fluctuations in the abundance of the species by means of a generalized linear model. Mean bottom temperature and salinity fields were graphed and anomalies for this period were estimated. During 1998 and 2002 the highest and lowest mean temperatures were recorded, respectively, showing the most remarkable anomalies. Highest mean salinity was recorded during 1999 and in terms of anomalies during 2003 lowest salinities were recorded for the whole area. Highest juvenile concentrations were found in waters with bottom temperatures between 7ºC and 10ºC and salinities between 33.3 and 33.8 distributed to the north and within the San Jorge Gulf and in midshelf between the 50 m and 100 m isobaths, to the southern zone of the Valdés Peninsula. Adult concentration was higher at the centre of the shelf, decreasing towards the coastal sector, at approximately 6ºC and 9ºC and between 33.4 and 33.9. Regression coefficients evidenced highest juvenile abundances in shallow areas with low salinity, and highest adult abundances in regions with low temperature and high salinity. No spatial shifts in the distribution of the species were observed during marked temperature or salinity anomalies.Key words: Geographical distribution, temperature fields, salinity gradients, Southwest AtlanticResumen.-Se analizaron las variables de temperatura y salinidad en el invierno durante el período 1996-2003 en el área de distribución del efectivo patagónico de la merluza argentina Merluccius hubbsi; estas variables oceanográficas se relacionaron con las variaciones en la abundancia de la especie, a través de un modelo lineal general. Se determinaron los campos medios de fondo y las anomalías de temperatura y salinidad para ese período. El año 1998 presentó la temperatura promedio más alta y el 2002 la más baja, indicando las anomalías más destacadas. La salinidad promedio más alta se registró en 1999 y en términos de anomalías, el 2003 fue, en toda el área, de menor salinidad. Las mayores concentraciones de juveniles se observaron en aguas con temperaturas de fondo entre 7°C y 10°C y salinidades entre 33,3 y 33,8 distribuidas en el interior y norte del Golfo San Jorge y en la plataforma media, entre la isóbata de 50 y 100 m, hasta la zona sur de la Península Valdés. La distribución de adultos se concentró en el centro de la plataforma, disminuyendo hacia el sector costero, aproximadamente entre 6º y...
The Argentine hake Merluccius hubbsi represents the dominant demersal fish and one of the main fisheries in the Argentine Sea. We analyzed over 17 years (September 1997–February 2015) of satellite surface chlorophyll concentration (CHL) and sea surface temperature anomaly (SSTA) data in the main spawning (SUB) and nursery (SJG) areas of the Patagonian stock of M. hubbsi. The variability observed in these environmental conditions was related to interannual differences in the reproductive success of hake. CHL values were maximum during austral spring (October–November) and minimum during winter (June–August). Blooms started in late September and lasted on average 128 and 110 days at SUB and SJG, respectively. At SUB, average CHL at the time of reproduction, the day of occurrence of the maximum chlorophyll concentration, and fall SST anomalies were significantly related to recruitment (RVPA) a year later and to two Larval Survival Indices (LSISSB and LSITEP) considered. At SJG, RVPA, LSISSB, and LSITEP showed negative correlations with fall (March–May) SSTA. Total egg production was not related to fall SSTA or spring phytoplankton dynamics at SUB or SJG. Significant positive trends were observed in the time series of CHL and SSTA in the study area. The trends observed in CHL represent average increases of 40.7% and 35.7% since 1997 at SUB and SJG, respectively. The potential implications of long‐term changes in environmental conditions for hake reproductive success are discussed.
The geographical and seasonal distribution of Cladocera was studied in the Argentine Sea, from the Río de la Plata River (34°S) to the Patagonian area (47°S). The cladoceran community included six species, which were found in the plankton especially in spring and summer and were absent during winter. Evadne nordmanni and Podon intermedius were the most widely distributed species, from 34°S to 44°S, in coastal and mid-shelf waters (MSW). Their Temperature-Salinity ranges of occurrence were around 8-21.7°C and 18-36.4%. High numbers of E. nordmanni and P. intermedius were observed in the weakly stratified waters of the northpatagonian tidal front (42°S-45°S) compared to the other sectors of the frontal system. Pleopis polyphemoides mainly appeared north of 39°S in waters influenced by the Río de la Plata estuary (18-36.5%) and it showed preference for warm waters. Podon leuckarti was present only in a few samples from cold coastal and MSW between 38°S and 44°S and seemed to be a stenohaline species (33.4-34.2%). Penilia avirostris and Pseudoevadne tergestina were found north of 39°S particularly in coastal and MSW, but also in tropical and subtropical waters. Their Temperature-Salinity ranges of occurrence were 14-20.5°C and 27-36.5%. Although the highest densities of Cladocera were found in neritic waters, our data suggests that some species may also inhabit oceanic waters. During early spring, E. nordmanni, P. polyphemoides, P. intermedius, and P. leuckarti were the first species to appear in the plankton in coastal waters off the Buenos Aires province, followed by P. avirostris and P. tergestina which gradually replaced the previously mentioned species and were dominant during the following summer. All species were absent during autumn and winter.
• Abstract: Diel vertical migrations of the marine dinoflagellate A. excavatum were followed in a laboratory water column, and the effects of temperature stratification and nitrogen depletion on patterns of migration were examined. It was found that A. excavatum is a vertical migrator aggregating at surface durlng daylight, and descending at night. A six-degree thermocline did not restrict its migration but delayed the vertical movements. Nitrogen depletion in the culture was correlated with earlier downward migration in the day, and nitrate assimilation in the dark was confumed In another essay, with a nitrogen deficient culture, nocturnal nitrate uptake per cell was measured. It is suggested that the ability ofA. excavatum to take up nitrate in the dark working together with diurnal vertical migration could be important mechanisms regulating bloom developments.
Comprender las causas que generan la variabilidad del reclutamiento en las poblaciones marinas constituye uno de los mayores desafíos de la ciencia pesquera. Nuestra capacidad predictiva para explicar estas variaciones es relativamente baja, debido a la interacción de factores exógenos y endógenos, que varían en el tiempo y el espacio dentro de las poblaciones. Con el fin de obtener información sobre las fluctuaciones en el reclutamiento de la merluza argentina (Merluccius hubbsi) del stock patagónico, revisamos los resultados obtenidos analizando la ecología reproductiva, la dinámica trófica y energética durante las diferentes etapas de desarrollo de esta especie y su relación con variables ambientales. Observamos que el potencial reproductivo está fuertemente influenciado por las características parentales, particularmente de las hembras, en cuanto a su tamaño, edad y condición. Esta característica, denominada “efecto materno”, sugiere que la biomasa de la población reproductora, comúnmente utilizada como índice de productividad en la evaluación de pesquerías, es un predictor deficiente del reclutamiento. También observamos que la supervivencia durante los primeros años de vida de la merluza se ve afectada por la coincidencia espacial con el Sistema Frontal Norpatagónico, caracterizado por una alta concentración de nutrientes, alta productividad y disponibilidad de alimento. Las condiciones físicas y la densidad larvaria en la zona de crianza afectaron el estado nutricional y la mortalidad de la merluza, principalmente por competencia por alimento o depredación. Se observó que la transición del hábitat pelágico al demersal en los juveniles se produce durante un período más extenso que el reconocido anteriormente para esta especie, lo que destaca la importancia de utilizar los registros acústicos para complementar la información de las redes de arrastre de fondo. Este es uno de los principales temas a desarrollar para estimar nuevos índices de reclutamiento de merluza argentina, junto con otras líneas de investigación propuestas para mejorar la evaluación del stock.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.