1.- INIDEP - Publicaciones seriadas

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Browsing 1.- INIDEP - Publicaciones seriadas by Subject "Age composition"

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    Estructura por edad y sexo de la captura de merluza desembarcada. Período 1986-1998
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Renzi, M.A.
    During the 1986-1998 period the hake (Merluccius hubbsi) fishery in the Argentine Sea (SW Atlantic) turned from moderate to intense exploitation. Age and sex structure analysis showed a change in the exploitation pattern. During the three periods defined 1986-1989, 1990-1992 and 1993-1998 a trend towards catching young individuals and a predominance of females age 3 and older was observed. An increase of total mortality was also detected. As a consequence of the establishment of a closed area in mid 1997 ice-chilling and freezer fleets changed operation areas which brought about differences in the catch structure. Freezers showed higher percentages of older ages. An average decrease of 30 in yield number of individuals per unit effort for all ages was also observed.
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    Estructura por edad y sexo de la población de merluza
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Renzi, M.A.; Santos, B.A.; Simonazzi, M.
    Hake Merluccius hubbsi population structure in 1993, 1994, 1996, 1997 and 1998 and age and sex distribution during 1997 are analyzed. Data were obtained in research surveys. At the end of winter 1997 concentrations of juveniles were found in the San Jorge Gulf Argentine Sea, SW Atlantic, with maximum yields of 10,000 individuals per trawl hour for age 1 and 2,500 individuals per trawl hour for age 2. The highest concentrations of adults were found in the Gulf and South of 47°S, between the 100 and 200 m isobath, maximum yields of up to 1,700 individuals per trawl hour for age 3 and up to 90 individuals per trawl hour for age 7 and older. In spite of the decrease in population abundance, the basic age structure juveniles, young adults and old adults was stable in the period studied. Sex ratio of total population was approximately 1:1. Nevertheless, when sex and age proportion was estimated it was observed that, as of age 3, females were more abundant than males. The highest mortality rates for both sexes in the 1996-1997 period were observed in ages 3 and 4in 1997-1998 they corresponded to ages 6 and 7.
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    Estudio de edad y crecimiento de la sardina fueguina (Sprattus fuegensis) de las costas de la provincia de Santa Cruz e Islas Malvinas
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1982) Cousseau, M.B.; Gru, D.L.
    Samples of Sardina fueguina (Sprattus fuegensis) were taken during research cruises carried out in 1974 and 1978. Length and age frequency distributions were analyzed, and von Bertalanffy growth parameters were calculated for the coastal waters of two geographical regions: Province of Santa Cruz and northern part of Malvinas Islands. Lenght and weight growth curves have been calculated for each region and each year. Marked differences have been found between gowth parameters of both regions, and the calculated values showed a good fit with the observed ones. According to these results, it is possible to assume that the sardines of both regions constitute two different populations. However, more information on the total distribution of the species will have to be obtained in order to confirm the present observations.
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    Estudios de distribución de la anchoíta (Engraulis anchoita) en un área de extensión reducida. I. Densidades mínimas de muestreo para la estimación de algunos parámetros poblacionales
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Gru, D.L.; Hansen, J.E.
    Results of a research cruise carried out to estimate some biological parameters of anchovy (Engraulis anchoita), during the major spawning season, were analyzed in order to determine the minimum number of samples required to obtain unbiased values. Twelve samples of fishes were taken within an area of 607 nm². Size (total length)distributions, slope of the length-weight relationship, sex ratio and age population structure were considered. Results suggest that those parameters should be estimated by eight or more samples (corresponding to 76 nm² each).
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    Resultados de una campaña de investigación sobre la anchoíta (Engraulis anchoita) del sector bonaerense en el otoño de 1983. Distribución, abundancia y algunos aspectos biológico-pesqueros
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 1986) Hansen, J.E.; Gru, D.L.; Perrotta, R.G.
    An extensive area of the continental shelf -between 37°20' and 34°40'S - was reviewed through hidroacoustical methods in order to evaluate the anchovy biomass. Within the area of highest concentration, further data on anchovy abundance were recorded, and fish samples were taken. Large anchovy shoals were located at about 170 nm from Mar del Plata, mainly in zones with sharp changes in oceanographic conditions. The distribution of the species was not uniform, but "contagious", and the log-normal distribution provided the best fit for the echo-integrator recorded data. The biomass was estimated at 1,061,727 tons (Confidence limits in between 921,010 and 1,223,930 tons). Some parameters of the population were estimated, such as: lenght-weight relationship, von Bertalanffy growth curve constants, sex ratio, maturity, and age composition. Taking into account a calculated naturaly mortality rate of M= 0.85, a Maximum Sustainable Yield at about 451,000 tons was estimated (Confidence limits at about 520,000 and 390,000 tons).