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### Browsing by Author "Hernández, Daniel R."

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- ItemAnálisis y diagnóstico del diseño de muestreo de las campañas de evaluación de merluza (Merluccius hubbsi) al norte y al sur de los 41°S (Zona Comun de Pesca Argentino-Uruguaya y Mar Argentino). Años 1996-1999(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Hernández, Daniel R.; Bezzi, S.I.; Ibañez, P.M.
Show more Gain contribution by stratification in hake (Merluccius hubbsi) biomass estimation with respect to a simple random sampling based on the same sample size is analyzed. Considering as objective hake biomass assessment, curves which relate precision reached in estimations to the sample size are established. Data were from total hake biomass surveys carried out from 1996 through 1999 hake management units distributed North and South of 41°S Argentine Sea are analyzed separately. Stratification used at present allows to obtain very variable gains in precision associated to biomass with estimations, in the North management unit, with a maximun of 88 in 1996 and no gain in 1997. The South management unit presents also variable results but always with important gains. The applied sampling effort levels allow to obtain biomass estimation relative errors no higher than 29 in the assessment corresponding to the North management unit and 14 in the assessment relative to the South management unit. These values may be considered as very satisfactory. In the event of further diminishing estimation errors to obtain minimum gains it will be necessary to increase the sampling effort to levels which are inadmissible from a practical point of view. It does not seem feasible to diminish the present error of biomass estimation in both management units.Show more - ItemAplicación 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.
Show more 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.Show more - ItemÍndices ponderados de abundancia relativa, obtenidos a partir de modelos lineales generalizados, considerando la presencia de valores nulos de captura.(Instituto Nacional de Investigación y Desarrollo Pesquero, 2017) Hernández, Daniel R.; Pérez, Marcelo; Cortés, Federico
Show more General Linear Models (GLM) and generalized linear models (GLMs), that allow to integrate in a simple way the different factors that influence catch per unit of effort (CPUE) variation, are used to estimate annual abundance indices. The effect associated to the Year factor is considered and, based on the results obtained, the index is built. Nevertheless, when significant interactions that include said factor occur, the result is indices proportional to the mean annual abundance of each year with proportion coefficients that depend on the year, which does not allow to compare the series terms. In this paper the weighted abundance indices obtained with the GLM and GLMs are established and how to define the population mean annual density as a function of the parameters of the models used is considered. An application example with null CPUE values in patagonian smoothhound is shown and debate on the correct selection of the fleet to provide the data used to estimate annual weighted abundance indices presented.Show more - ItemInfluencia de las interacciones con el factor Año en los índices anuales de abundancia obtenidos por modelos lineales generales utilizando datos de Captura por Unidad de Esfuerzo(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Hernández, Daniel R.; Perrotta, Ricardo G.
Show more The problem in the definition of a relative annual abundance index using a General Linear Model is posed. The possible factors generating changes in the catch per unit effort (CPUE) are discussed and the parameterization of the model is analyzed, in particular the Sigma-restrictive parameterization. This report considers the problem caused by the presence of interactions of first order that include the factor Year in the model. It has been mathematically demonstrated that in the presence of these interactions, the index series is not proportional to the abundance annual mean of the resource. An approach of practical order to evaluate the possible effect of the interactions that include the factor Year in the index is considered using the percentage of explained variance of the model with and without these interactions. Some methodological rules are also defined to attenuate several problems generated by the mentioned interactions: (1) evaluating if type of fleet, included as categories of the factor Ship, has experienced modifications throughout the period of study that could have generated changes in the efficiency of fishing units; (2) allowing for the possibility of working with indexes pondered by Area; (3) using the most convenient categorization for the factor Month (month, bimonthly, quarterly, fishery season, etc.), considering the seasonal distribution of the resource and the activity of the fleet, as well as the limitations generated by the presence of empty cells in the design. Two application examples are presentedShow more - ItemModificación del análisis de cohortes de Pope para extender su aplicación a un rango más amplio de valores de mortalidad natural y mortalidad por pesca(Mar del Plata : Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2008) Hernández, Daniel R.; Perrotta, Ricardo G.
Show more Pope's Cohorts Analysis was modified to extend its application to a wider range of natural mortality, M and fishing mortality, F rate values. The modified method maintains the simplicity of the one established by Pope and does not require to resolve any non lineal equation in each cohort reconstruction process. The relative errors obtained when estimating the number of individuals per age (maximum and mean in absolute value) showed acceptable levels within the five domains (M and F pairs of values) analyzed in this work. The new method can be adapted to a particular situation (M and F values range) simply solving an optimization problem (minimization of the maximum relative error absolute value) easily achieved using a calculation sheet or considering the approximation corresponding to any of the domains herein analyzed.Show more - ItemMuestreo de desembarque de caballa (Scomber japonicus) en el puerto de Mar del Plata (38° S) y determinación de niveles de captura en el área El Rincón; período 1989-2003(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Perrotta, Ricardo G.; Garciarena, A. David; Hernández, Daniel R.
Show more Chub mackerel caught by the commercial fleet in El Rincón (39°-41° 30’ S) and Mar del Plata (38° S) areas was analyzed. In 2001 and 2002 samples from El Rincón were obtained from landings or collected by scientific observers on board the commercial ships. Samples from Mar del Plata were acquired during the 2001-2002 and 2002-2003 fishing seasons, on board two vessels of the small purse-seine fleet. Landings were mostly adults and only a small fraction of juveniles was observed (< 5%). Length growth parameters from El Rincón samples were estimated, and length-weight and length-age relationships were fitted by Least Squares. The results were as follows: L(mm) = 538.4; k (years-1) = 0.122; t0 (years) = -4.92; Pt = 4*10-7 * Lt 3.536. Natural mortality was estimated at 0.30 and age limit at 10 years. The standardized catch per unit effort (CPUE) annual mean (kg h-1) for the 1990-2002 period was calculated by means of a General Linear Model which justified 41% of total variance. The most significant variables resulted to be the seasonal pattern of exploitation of the resource (month), and its pronounced concentration in the exploitation area (fishing position). Values of the standardized CPUE annual mean fluctuated with trends that were similar to those registered between 1993 and 2002. Due to fluctuations in the Chub mackerel abundance and the possible negative effect caused by the activity of large ships in El Rincón, a maximum annual catch of 13,000 t for 2003 is suggested for this area as a precautionary measure.Show more - ItemNematodes parásitos como indicadores biológicos de Macruronus magellanicus(Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2006) Incorvaia, I.S.; Hernández, Daniel R.
Show more A wide distributional range species can constitute many populations or fishing stocks which can be whole or partly overlapped within their distribution area, reason why they must be clearly identified. Therefore, proper identification of stocks is necessary for fisheries management, as this is the unit to which the fishing effort should be applied. The parasitological method is one of the systems currently used to determine stock. Nematodes parasites of Macruronus magellanicus (longtail hake) collected during surveys enmarked between 45º S-55º S in the Southwest Atlantic were studied. Nematodes that could be used as biological indicators were selected. Mean abundance values of L3 Anisakis simplex and Hysterothylacium aduncum were estimated. Three different areas of abundance were recognized: coastal with high abundance, intermediate with mixed values and continental slope with low abundance.Show more