INIDEP Informe Técnico Nro 51 (2003)

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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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    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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    Pesca comercial de merluza al sur de 41°S y estimación de índices de abundancia derivados de la flota pesquera
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Irusta, G.; Pérez, M.; Renzi, M.A.; Castrucci, R.
    The activity of fishing fleets for hake Merluccius hubbsi south of 41°S Argentine Sea, SW Atlantic, is described. In order to establish the standard group of vessels, density indices derived from research cruises and ice-chilling fleets were related. Group four 1,400-1,800 HP related better to the abundance trend. Also, two series of indices associated to different fractions of the population were estimated: juveniles age 2) and adults age 3-5. Finally, a total catch per unit effort CPUE for the region south of 41°S, which showed a declining trend during the period considered 1991-1997, was calculated.
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    El descarte en la flota comercial argentina dirigida a la pesquería de merluza. Período 1990-1997
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Dato, C.V.; Villarino, M.F.; Cañete, G.R.
    Discards of the commercial fleet in the Argentine Sea (SW Atlantic) directed to hake Merluccius hubbsi were estimated in weight and number of individuals. The dynamics of the ice-chilling and freezer fleets per area and quarter and processes of discarding were analyzed. The estimation method was based on the comparison of landings and surveys length composition, the latter filtered by the selectivity of the mesh used by the commercial fleet to rebuild the length distribution of catches. It is concluded that discards had an annual variation of 42,000 t-148,000 t in the 1990-1997 period, which represented between 30 and 50 in weight and 11-24 in number of actual catches. The analysis of age groups affected by discards showed that over 90 corresponded to individuals age 1 and the rest to specimens age groups 0-2.
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    Índice de abundancia del grupo merluza de edad 2 en el área de cría patagónica. Período 1995-1998
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Castrucci, R.; Aubone, Aníbal; Pérez, M.; Renzi, M.A.
    An abundance index of hake Merluccius hubbsi individuals age 2 was estimated in the nursery area south of 41°S Argentine Sea, SW Atlantic. The analysis comprised the 1995-1998 period and was made with data derived from research surveys programmed to that end. A mean value estimator of CPUE catch in number of individuals per trawl hour based on delta distribution was used. The spatial distribution of CPUE of age groups 1 and 2 in the area surveyed, total length distribution per survey and the corresponding age composition are presented. The declining trend of abundance index of hake age 2 observed during the four year period amounted to 52.9.
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    Relación largo-peso y largo-edad de primera madurez sexual de la merluza
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Simonazzi, M.
    Estimations were made on the basis of a subsample of 6,734 individuals of Merluccius hubbsi from the Argentine Sea south of 41°S. Length-weight relation potential regression parameters were a=0.00950863, 0.01093448 and 0.01096117b=2.90831652, 2.86558431 and 2.86583191 for males, females and total individuals, respectively. The Newton algorithm was used to minimize the residuals. Maturity ogives were estimated with the logistic model adjusted by no lineal minimum quadratic ordinates. Length at first maturity at 50 was 33.79 cm for males and 35.38 cm for females. Age at first maturity estimated with the same model adjusted to the time elapsed from birth to catching was 2.61 and 2.67 years for males and females, respectively. Good fitting in all regressions was obtained.
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    Aplicación de un modelo dinámico de biomasa para evaluar el efectivo sur de merluza. Período 1986-1998
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Irusta, G.; Hernández, Daniel R.
    The status of hake (Merluccius hubbsi) resource south of 41°S in the Argentine Sea was evaluated with the Biomass Dynamic Model of Pella and Tomlinson. Results indicate that the population was overexploited and in a low biological production level (B99 BMSY1 because, as of 1998, catches always exceeded the surplus production corresponding to each year and the (MSY) Maximum Sustainable Yield. In 1993 increase of landings accelerated declination of biomass. For 1999 the MSY was estimated at 244,773 t and the replacement catch at 147,389 t. Landings corresponding to 1998 surpassed the MSY in 145,000 t and the replacement catch in 242,611 t.