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Gabriel J Torres - One of the best experts on this subject based on the ideXlab platform.

  • intra annual growth variations of young of the year hake Merluccius hubbsi of the uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (<25 cm TL) and its intra-annual variations are analyzed. A total of 307 individuals was collected in the Uruguayan continental shelf, covering the four seasons of the year. Pelagic, demersal and first-year ring otolith measurements and otolith border type characteristics are taken into account. The growth that occurred between the time of hatching and the first-year was different for individuals collected in different seasons. Summer season was found to have the smallest averages (p < 0.05) for pelagic, demersal and first-year rings. Different spawning times and variability in the environmental features throughout the year could affect the growth characteristics of M. hubbsi juveniles. Juveniles from autumn to winter spawning would mark their first-year in the following winter and would take longer to get to each of the analyzed rings. However, juveniles from spring spawning also mark the first-year in the following winter but, would show shorter life periods related to otolith and rings developments. The demersal ring formation showed significant differences between autumn and spring. This ring indicated the change between pelagic and demersal habitat. The temporal variation in the upper mixed layer and thermocline development throughout the year could be the cause of differences in growth development and behavior. Our current understanding of mesoscale physical processes suggests that these changes associated with biological interactions may play an important role in juvenile recruitment. Further investigations of mesoscale physical processes are needed to confirm these hypotheses.

  • Intra-annual growth variations of young-of-the-year hake (Merluccius hubbsi) of the Uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (

Walter Norbis - One of the best experts on this subject based on the ideXlab platform.

  • intra annual growth variations of young of the year hake Merluccius hubbsi of the uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (<25 cm TL) and its intra-annual variations are analyzed. A total of 307 individuals was collected in the Uruguayan continental shelf, covering the four seasons of the year. Pelagic, demersal and first-year ring otolith measurements and otolith border type characteristics are taken into account. The growth that occurred between the time of hatching and the first-year was different for individuals collected in different seasons. Summer season was found to have the smallest averages (p < 0.05) for pelagic, demersal and first-year rings. Different spawning times and variability in the environmental features throughout the year could affect the growth characteristics of M. hubbsi juveniles. Juveniles from autumn to winter spawning would mark their first-year in the following winter and would take longer to get to each of the analyzed rings. However, juveniles from spring spawning also mark the first-year in the following winter but, would show shorter life periods related to otolith and rings developments. The demersal ring formation showed significant differences between autumn and spring. This ring indicated the change between pelagic and demersal habitat. The temporal variation in the upper mixed layer and thermocline development throughout the year could be the cause of differences in growth development and behavior. Our current understanding of mesoscale physical processes suggests that these changes associated with biological interactions may play an important role in juvenile recruitment. Further investigations of mesoscale physical processes are needed to confirm these hypotheses.

  • Intra-annual growth variations of young-of-the-year hake (Merluccius hubbsi) of the Uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (

María Inés Lorenzo - One of the best experts on this subject based on the ideXlab platform.

  • Growth pattern of the young of the year Argentine hake Merluccius hubbsi Marini, 1933 (Gadiformes Merluccidae) along the Brazilian and Uruguayan coasts
    Environmental Biology of Fishes, 2011
    Co-Authors: María Inés Lorenzo, André M. Vaz-dos-santos, Carmen Lúcia D. B. Rossi-wongtschowski
    Abstract:

    Morphology and morphometry of the sagittae otolith were studied in young of the year Argentine hake, Merluccius hubbsi in the Southeastern Atlantic. Geographical variation in the growth pattern of the young of the year Merluccius hubbsi was correlated with the differences found in otolith morphometry, relative growth, ring positions, as well as the formation of a new ring. The otolith development of M. hubbsi throughout its area of distribution accompanies an increasing northward temperature gradient, resulting in bigger otoliths and greater variability of ring position from northern to southern area. The canonical discriminate analysis showed that the otolith length and height explained most of the variation of the first discriminant function. We found significant differences in the discriminant scores between those samples from northern and southern area. As regards the Uruguayan coast and Southern Brazil, age groups zero shared some similarity as well as differences in growth; environmental features explain these differences but their effect on the adult fishes growth is still unknown.

  • intra annual growth variations of young of the year hake Merluccius hubbsi of the uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (<25 cm TL) and its intra-annual variations are analyzed. A total of 307 individuals was collected in the Uruguayan continental shelf, covering the four seasons of the year. Pelagic, demersal and first-year ring otolith measurements and otolith border type characteristics are taken into account. The growth that occurred between the time of hatching and the first-year was different for individuals collected in different seasons. Summer season was found to have the smallest averages (p < 0.05) for pelagic, demersal and first-year rings. Different spawning times and variability in the environmental features throughout the year could affect the growth characteristics of M. hubbsi juveniles. Juveniles from autumn to winter spawning would mark their first-year in the following winter and would take longer to get to each of the analyzed rings. However, juveniles from spring spawning also mark the first-year in the following winter but, would show shorter life periods related to otolith and rings developments. The demersal ring formation showed significant differences between autumn and spring. This ring indicated the change between pelagic and demersal habitat. The temporal variation in the upper mixed layer and thermocline development throughout the year could be the cause of differences in growth development and behavior. Our current understanding of mesoscale physical processes suggests that these changes associated with biological interactions may play an important role in juvenile recruitment. Further investigations of mesoscale physical processes are needed to confirm these hypotheses.

  • Intra-annual growth variations of young-of-the-year hake (Merluccius hubbsi) of the Uruguayan continental shelf based on otolith analysis
    Fisheries Research, 1999
    Co-Authors: Walter Norbis, María Inés Lorenzo, Gabriel J Torres
    Abstract:

    The growth of young-of-the-year hake (Merluccius hubbsi) (

Gustavo J. Macchi - One of the best experts on this subject based on the ideXlab platform.

  • Maternal condition, fecundity and oocyte quality of Argentine hake (Merluccius hubbsi) from the Northern stock
    Fisheries Research, 2018
    Co-Authors: Karina Andrea Rodrigues, Gustavo J. Macchi, Ezequiel Leonarduzzi, Maria Ines Militelli
    Abstract:

    Abstract The influence of the condition of spawning females on fecundity and oocyte quality, measured using morpho-physiological and biochemical indices, was analyzed for the Northern stock of Argentine hake ( Merluccius hubbsi ). First the relationships between morpho-physiological and biochemical indices were analyzed, and if they were influenced by female size. Samples of spawning-capable females were collected during the main reproductive peak of this stock in May 2011. The hepatosomatic index (HSI) in M. hubbsi was a good indicator of lipid concentration for both the liver and muscle. HSI and the relative condition factor (Kn) were independent of female size. Muscle protein content was positively associated with maternal attributes. Relative fecundity ranged between 287 and 916 hydrated oocytes g −1 and showed significant positive relationships with GSI and Kn. The dry weight of hydrated oocytes (n = 100) ranged between 2.65 and 4 mg and was positively related with the HSI. The oil droplet diameter of hydrated oocytes varied between 250 and 292 μm and was also positively related with HSI, Kn, liver and muscle lipid content, suggesting that it could be a good indicator of the nutritional condition for hake females of the Northern spawning stock.

  • Biology and fishery of the Argentine hake (Merluccius hubbsi)
    2016
    Co-Authors: Gabriela Irusta, Gustavo J. Macchi, Elena Louge, Karina Andrea Rodrigues, Luciana L. D'atri, María F. Villarino, Betina A. Santos, Mario Simonazzi
    Abstract:

    La merluza (Merluccius hubbsi) es una especie demersal euritermica y eurihalina asociada a aguas subantarticas de la plataforma y el talud continental. La especie, considerada el principal recurso pesquero de la Argentina que en 2011 alcanzo los maximos niveles de captura y exportacion, se distribuye desde el sur de Brasil hasta los 55° S en un rango de profundidad de 50-400 m. Los tres stocks identificados, ubicados entre los 34°S-41°S, al sur de dicha latitud y en el Golfo San Matias, muestran diferencias en lo relativo a areas y epocas de reproduccion y cria, caracteres meristicos y morfometricos, niveles de abundancia y parametros de crecimiento. En el Instituto Nacional de Investigacion y Desarrollo Pesquero (INIDEP) se realizan evaluaciones anuales del estado de explotacion de los stocks que se encuentran al norte y sur de los 41° S y se brindan recomendaciones a la administracion pesquera. En el presente capitulo se describen la biologia, caracteristicas de la pesqueria, abundancia y estructura poblacional y recomendaciones de manejo para los dos principales stocks de merluza.

  • Comparative study of spawning pattern and reproductive potential of the Northern and Southern stocks of Argentine hake (Merluccius hubbsi)
    Journal of Sea Research, 2015
    Co-Authors: Karina Andrea Rodrigues, Gustavo J. Macchi, Maria I. Militelli
    Abstract:

    Abstract The reproductive biology of the Northern (Bonaerense) and Southern (Patagonian) stocks of Merluccius hubbsi in the Argentinean Sea is analyzed, including information on spawning areas, estimates of abundance and size composition of spawning females, fecundity, spawning frequency and egg quality. Samples of Argentine hake were obtained during the period of peak reproductive activity; May and January for the Northern and Southern stocks, respectively. The size of the reproductive area for the Northern stock (35–38°S) was clearly smaller than the one estimated for the Southern population (43°30′–46°S), being 23,770 km 2 and 52,460 km 2 respectively. Spawning females from the Northern reproductive area were smaller (modal values between 35 and 40 cm TL) than those from the Southern stock (modal values between 38 and 50 cm TL), and they were also less abundant in number and had a lower spawning frequency (8–13 days and 5–7 days between partial spawning for the Northern and Southern stocks respectively). No differences in batch and relative fecundity between stocks were recorded (mean values of 526 and 530 hydrated oocytes g − 1 ), but the dry weights of hydrated oocytes from females of the Northern group were higher (3.08 mg for 100 hydrated oocytes) than those of the Patagonian stock (2.84 mg) for the same total length range. The egg production during the month of peak spawning of the Northern group depended mostly on the smaller females ( 12 –22 × 10 12 eggs and 692 × 10 12 –1295 × 10 12 eggs for the Northern and Southern stocks respectively). Those differences in egg production and the high productivity and retentive characteristics described for the spawning area and nursery ground in Patagonian waters would justify the greater abundance and resilience of the Southern stock of Argentine hake. The low abundance of females in spawning capable stage observed during the reproductive season of the Northern group (autumn–winter), led us to postulate that currently it does not exist a pronounced reproductive peak in this stock similar to the one observed for the Southern hake group during the summer.

  • Larval condition of Merluccius hubbsi (Marini, 1933) in the northern Patagonian spawning ground
    Fisheries Research, 2014
    Co-Authors: Marina V Diaz, M. Pilar Olivar, Gustavo J. Macchi
    Abstract:

    a b s t r a c t Argentinean hake, Merluccius hubbsi, is one of the most important fishery resources of the South-western Atlantic Ocean, but its spawning biomass decreased in the last fifteen years, mainly due to the increased fishing pressure. It is widely accepted that to understand recruitment variability is necessary to study the factors that determine survival of early stages of development. Nutritional condition indexes have been widely used to determine starvation in wild larvae. In the present investigation, condition of M. hubbsi larvae was estimated employing field collected material by means of RNA/DNA index. This is the first attempt to use this index in this species. The change in the RNA/DNA index showed a clear ontogenetic pattern: increasing from preflexion to postflexion stages, showing an apparent decrease at the end of postflexion stage and a conspicuous increase once transformation stage was achieved. This pattern could be indicating that the transition between postflexion and transformation stages might represent a critical phase along larval development. RNA/DNA index also showed significant differences between areas from the spawning grounds characterized by different chlorophyll a concentration and abundance of potential prey. The study of nutritional condition represents a useful tool for identifying favorable nursery areas, providing valuable information for a comprehensive management of a population subject to overfishing.

  • Vertical distribution of hake Merluccius hubbsi in spawning aggregations in North Patagonian waters of the Southwest Atlantic
    Fisheries Research, 2013
    Co-Authors: Martin D Ehrlich, Gustavo J. Macchi, Adrián Madirolas, Laura Machinandiarena
    Abstract:

    Abstract During hydroacoustic surveys for the Argentine hake ( Merluccius hubbsi ) stock assessments carried out in December 1996, 1998 and 2000 in the main spawning area, a bottom and mid water trawl daylight and darkness sequence per year was selected to study vertical migration. Dense pelagic layers were observed during day and night in the echograms and sometimes a fish layer remained on the bottom at night. During daylight, hake were concentrated mainly near the bottom. The size frequency distributions of males and females differed significantly among the three surveys. Male dominance was observed in 1998 and 2000 surveys. Lack of actively spawning females at mid-water levels during darkness may be partly due to reproductive courtship in which females could abandon the shoals during egg fertilization. In the 1996 survey, females dominated both evening and night, before spawning. Just before spawning, sex ratio became similar. Spawning might occur early in the morning because actively spawning females had hydrated oocytes or recent post ovulatory follicles and males were dominant. Also, high densities of recently fertilized eggs were observed early in the morning during the three surveys.

Brenda Temperoni - One of the best experts on this subject based on the ideXlab platform.

  • Are hakes truly opportunistic feeders? A case of prey selection by the Argentine hake Merluccius hubbsi off southwestern Atlantic
    Fisheries Research, 2019
    Co-Authors: Mauro Belleggia, Brenda Temperoni, Gustavo Álvarez-colombo, Nadia Marina Alves, Melisa Mariana Leyton, Diego Giberto, Claudia S Bremec
    Abstract:

    Abstract Prey selection and feeding strategy of the Argentine hake Merluccius hubbsi were investigated by analyzing the diet and prey availability in the main nursery area of the Patagonian stock (42.4°–46.4 °S, 70–102 m depth). Stomach contents from fish captured using a bottom trawl net, and zooplankton samples collected with a Bongo net, were analyzed. Acoustic data were examined to identify pelagic aggregations and quantify relative prey abundance. The Argentine hake M. hubbsi fed mainly on crustaceans (92.7%IRI), followed by fish (7.1%IRI) and cephalopods (0.2%IRI). Among crustaceans, the diet was dominated by euphausiids ( Euphausia spp.), the lobster krill Munida gregaria , and the hyperiid amphipod Themisto gaudichaudii . The most consumed fish was other hake by cannibalism. Prey availability was also numerically dominated by the euphausiids ( Euphausia spp.), followed by the hyperiid amphipod T. gaudichaudii and the lobster krill M. gregaria . Ontogenetic dietary changes were detected: consumption of euphausiids and amphipods decreased with predator´s total length, and the consumption of the lobster krill M. gregaria was higher in adult specimens. The Argentine hake M. hubbsi showed positive prey selection for lobster krill M. gregaria. The consumption of Euphausiids decreased with the increasing acoustic abundance of the lobster krill M. gregaria. The cannibalism was denso-independent. The Argentine hake appeared to be opportunistic when the proportion of prey eaten to the proportion present in the environment was compared, but deeper analyses confirmed that zooplankter with increased abundances and higher energy density was the preferred prey.

  • effect of nursery ground variability on condition of age 0 year Merluccius hubbsi
    Journal of Fish Biology, 2018
    Co-Authors: Brenda Temperoni, Agueda Massa, Carla Derisio, Patricia Martos, Carla Berghoff, Maria Delia Vinas
    Abstract:

    : This study examined the southern or Patagonian (41°-55° S) stock of Argentine hake Merluccius hubbsi, the more abundant of the two stocks on the Argentinean continental shelf. Pre-recruits (age 0+ year individuals) of this stock settle and grow in the San Jorge Gulf (45°-47° S, 65° 30' W), a complex habitat with large spatial variability in environmental features. Relative condition factor, hepatosomatic index, lipid content and fatty-acid composition of muscle and liver, and diet information were combined with physical and biological data to evaluate: how nutritional status of age 0+ year hake varies spatially within the nursery ground; whether changes in condition are related to environmental factors and feeding; whether the indices are interchangeable metrics of condition. Both morphometric and biochemical indices showed dissimilar spatial trends; enhanced liver-based condition coincided with low salinity nutrient rich waters, higher chlorophyll-a values and abundances of Euphausia spp., the preferred prey at most stations, suggesting a bottom-up effect on age 0+ year hake condition. Diminished condition at stations where Thermisto gaudichaudii was the main prey could derive from lower prey quality in terms of energy density and essential fatty acids content. Coastal waters of the gulf would be essential habitats for M. hubbsi pre-recruits. Future monitoring of condition with liver-based indices is encouraged in the gulf, where interannual increasing trends of satellite-derived chlorophyll-a values have been observed, which could have implications for recruitment of the species.

  • Larval growth of hake (Merluccius hubbsi) in the Patagonian shelf: Analysis of two reproductive seasons
    Fisheries Research, 2014
    Co-Authors: Paola Betti, Brenda Temperoni, Daniel Roberto Brown, Laura Machinandiarena, M Ehrlich
    Abstract:

    Abstract The Argentine hake ( Merluccius hubbsi ) represents the most abundant fish resource in the Southwest Atlantic Ocean. Larval age, daily growth, and temporal distribution of birthdates of individuals collected throughout two reproductive seasons (2004–2005 and 2009) were studied by analyzing daily growth increments in their sagittae otoliths. Samples were obtained in the Northern Patagonian shelf, which constitutes the main spawning area reported for this species. A total of 365 hake larvae sampled with different types of gears was used in this study. Back-calculated hatching periods extended from mid November to the end of March and several larval cohorts were identified. Length-at-age relationships were best described by exponential models: TL = 2.227 exp(0.032 t ) and TL = 2.581 exp(0.035 t ) (for 2004–2005 and 2009, respectively). Growth rates obtained by deriving the models ranged from 0.07 to 0.48 mm day −1 in 2004–2005, and from 0.09 to 0.74 mm day −1 in 2009. Differences in larval growth were detected between both periods and within them; differential growth would not be attributed to thermal effect since temperature values were quite similar along both seasons. Prey availability could explain the growth variation detected within the 2009 season.

  • Spatial patterns of copepod biodiversity in relation to a tidal front system in the main spawning and nursery area of the Argentine hake Merluccius hubbsi
    Journal of Marine Systems, 2014
    Co-Authors: Brenda Temperoni, Patricia Martos, M.d. Viñas, Marina Marrari
    Abstract:

    Abstract Copepods play an important role in marine ecosystems as a direct link of energy transfer between primary producers and higher trophic level consumers, such as fish. In the Argentine Sea, the Patagonian stock of Argentine hake Merluccius hubbsi spawns from late austral spring (December) to early autumn (April) in the northern Patagonian shelf region (43°–45°30′S), in association with a highly productive tidal front system. Since hake larvae prey mainly upon copepods, the objective of this study was to assess the spatial variability in the abundance and diversity of these potential food items in different sectors of the front, as one of the possible factors affecting hake recruitment success. Two complementary mesh sizes (67 and 300 μm) were used to accurately target the entire copepod size spectrum. The copepod community was dominated by developmental stages  Oithona helgolandica , Microsetella norvegica , Ctenocalanus vanus and Drepanopus forcipatus . Their spatial distribution was highly influenced by the across-shelf characteristics of the tidal front system, highlighting the impact of environmental features, mainly bottom temperature and salinity, in shaping the community. Abundances were higher in the transitional relative to the stratified sector of the system. Such sector would provide the appropriate conditions to sustain M. hubbsi larval growth resulting from high availability of adequate prey, the suitable thermal ranges, and the existence of retention mechanisms.

  • food and feeding of argentine hake Merluccius hubbsi larvae in the patagonian nursery ground
    Fisheries Research, 2013
    Co-Authors: Brenda Temperoni, Maria Delia Vinas
    Abstract:

    Abstract Feeding success during the early life stages of fish is one of the main factors that determines recruitment and stock fluctuations. In the Argentine Sea, the Patagonian stock of Merluccius hubbsi is the most important in biomass, spawning from December to April in the north Patagonian shelf region (43–45°30′). Since previous knowledge about larval feeding of the species in this region is fragmentary, adequate information is required for a complete assessment of its importance in the food web and its effect upon recruitment. Our primary objective was to examine the feeding strategy of M. hubbsi larvae in relation with prey availability in the nursery ground. Feeding incidence was 87%; hake larvae consumed mainly calanoid copepodites