2003 - INIDEP Informe Técnico Nro 50-56

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    Estudios sobre la factibilidad de una pesquería artesanal con palangres en los golfos y costa de la provincia del Chubut, Argentina
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Elias, I.; Pereiro, R.
    Artisanal fishing activities bivalve extraction through diving, hand-collection of octopuses and beach seine fishing are currently the only ways to exploit the coastal resources inhabiting the Argentine Northern Patagonian gulfs 42°43°S from the SW Atlantic. These are time-restricted activities. Diving and hand-collection are limited by management and sanitary policies while resource variability and commercial demand limit beach fishing. The objective of this work was to test a productive alternative, i.e., the use of longlines to increase and diversify catches in order to improve commercialization, contribute to a rational management and alleviate the pressure put on the resources exploited at present. Results obtained indicate that profitability of the activity in the gulfs would be favoured by the high yields reached during summer in the San Jose Gulf (0.700 kg hook and in the Nuevo Gulf in spring. The target species for the longline fishery would be the vitaminic shark (Galeorhinus galeus) and the cock fish Callorhynchus callorhynchus. Depending on the fishing grounds, selective catches of adult fish could be obtained with type 10 0 hooks in either bottom or mid-water longlines. On the other hand, this fishing circuit, complementary to bivalve extraction, would avoid displacement of artisanal fishermen from their natural and historic work environment, Valdes Peninsula.
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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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    Dinámica de la flota comercial argentina dirigida a la pesquería de merluza (Merluccius hubbsi) en el Mar Argentino. Periodo 1990-1997
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Dato, C.V.; Villarino, M.F.; Cañete, G.R.
    Since 1990, the Argentine commercial fleet directed to hake (Merluccius hubbsi) has obtained more than 70 of catches South of 41°S while to the North of this latitude the activity concentrated between 39°S and 41°S Argentine Sea, SW Atlantic. Bearing in mind the different characteristics of ice-chilling and freezer fleets, their activities were analyzed separately. Considering the relative percentages of catches declared in fishery statistics, the dynamics of each fleet is described per quarter and year. Special reference is made to 1997 when a closed area to protect juveniles was introduced between 44°S-47°S and 62°W-65°W. The freezer fleet activity, concentrated South of 41°S, especially South of 43°S, was stable throughout the period. It grouped around the closed area of Escondida Island during the summer 1st and 4th quarters) to disperse in deeper waters in winter 2nd and 3rd quarters. In the 2nd quarter it formed two nuclei, one to the North -and the most important- to the South of 41°S. The dynamics of the ice-chilling fleet per season was similar to that of the freezer fleetnevertheless, contrary to the latter, activities concentrated between 39°S and 42°S and, of the two nuclei formed in the 2nd quarter, the most important was the one North of 41°S. In 1995 a marked change was observed when concentration of the fleet ranged between 39°S and 42°S and the South nucleus practically disappeared.
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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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    La caballa (Scomber japonicus) y las condiciones del ambiente en el área "El Rincón" (39°40'-41°30' S) del Mar Argentino. Septiembre, 2000
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Perrotta, Ricardo G.; Viñas, M.D.; Madirolas, A.; Reta, Raúl; Akselman, Rut; Castro Machado, Federico; Garciarena, A. David; Macchi, Gustavo J.; Moriondo Danovaro, Paula; Llanos, V.; Urteaga, J.R.
    Between September 1st and 6th a research cruise was carried out in the Buenos Aires shelf area of "El Rincon" 39°40'-41°30'S, Argentine Sea SW Atlantic. The total area studied was 2,527.8 nautical mile2. Knowledge of the commercial fleet location at the time of the survey allowed to intensify sampling in a 'miniarea' of 52,8 nautical mile2. The acoustic assessment of chub mackerel (Scomber japonicus) biomass was 49,511.9 t, 94 of which corresponded to this last area. Fish samples coming from fishing trawls included only adult individuals of 240-460 mm total length (TL) and ages ranging 2-11 years. The limit age was estimated at 13 years and natural and total mortality rates at 0.23 and 0.54, respectively. Oceanographic conditions were those typical of the winter season, characterized by the vertical homogeneity of the water column in temperature and salinity. The isotherms and isohalines distributed parallel to the 50 m isobath with values progressively decreasing from the coast towards the slope. Salinity values allowed to detect two hydrographic regimes: that of the San Matias Gulf 33.8-34.4 located to the West and covering more than half of the study area and the one of the Shelf Waters 33.5-33.79 occurring towards the East. A positive gradient in chlorophyll a concentration was observed in N-S sense and from the coast towards the shelf break. The highest densities of phytoplankton, with dominance of diatoms, were observed in the southern sector. Low concentrations of Alexandrium tamarense and Prorocentrum minimum, two potentially noxious dinoflagellates, were detected. The highest zooplankton biomass associated to the highest salinity values and salinity gradients, represented mostly by Calanoides cf. carinatus, was also detected in the southern sector. The western sector, influenced by the San Matias Gulf regime and characterized by high densities of both, phytoplankton and zooplankton, may constitute a potentially favourable feeding ground for chub mackerel.
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    Estudios químicos y bacteriológicos del río Baradero (Argentina): calidad sanitaria del agua y aptitud de los peces para consumo humano
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Costagliola, Marcela; Seigneur, G.N.; Jurquiza, Verónica
    As a result of an agreement signed by the Municipal Government of Baradero Buenos Aires Province, Argentina and the INIDEP, the sanitary quality of the Baradero River waters was studied and fish safety assessed. Results of five field surveys carried out between 1993 and 1997 are studied. Organochlorine and organophosphorate pesticide residues, as well as traces of heavy metals were analyzed in 49 fish specimens and aerobic heterotrophic bacteria (AHB), total coliform bacteria (TC) and fecal coliform bacteria (FC) were counted out in 7 sampling stations placed on the coast and the riverbed. Alpha Hexachlorohexane, gamma Hexachlorohexane, beta Hexachlorohexane, Aldrin, Heptachlor epoxide, pp'DDE and Dieldrin were detected in fish tissues. The values of AHB found in different stations were not statistically different. The FC density on the coast was significantly greater than that found in the riverbed. Enterobacter cloacae, Morganella morganii, Proteus mirabilis, Escherichia coli, Aeromonas hydrophila and Non-O1 Vibrio cholerae were identified. It is concluded that the current levels of heavy metals and pesticide residues in fish are not dangerous for the average consumer nevertheless, further research is needed to assess the risk for groups with higher consumption rates, such as sport and subsistence fishers. On the other hand, there is microbiological pollution in the river owed to both, industrial wastewater and sewage discharges. The recorded bacterial stocks, pathogenic or potentially pathogenic, are susceptible to cause illnesses.
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    Análisis 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.
    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.
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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.
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    Descripción macroscópica de los ovarios del abadejo manchado (Genypterus blacodes). Escala de maduración
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2003) Machinandiarena, Laura; Villarino, M.F.; Cordo, H.D.; Macchi, Gustavo J.; Pájaro, Marcelo
    The macroscopic ovaric stages of pink cuskeel (Genypterus blacodes) females from the Argentine Sea (SW Atlantic) are described. They were classified in five stages of development based on changes in the appearance and size of the ovary: juvenile (I), developing (II), spawning (III), spent (IV) and resting (V).