2007 - INIDEP Informe Técnico Nro 62-67

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    Estadística pesquera de peces demersales australes en el Atlántico Sudoccidental (período 1980-2002)
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero, 2007) Gorini, Federico L.; Di Marco, Emiliano; Wöhler, Otto C.
    Fishery statistics of austral demersal fishes in the Southwest Atlantic (1980-2002 period). A synthesis of the information available about catches of austral demersal fishes and fishing efforts reported by different fleets that operated in the SW Atlantic between 34° S-58° S in the 1980-2002 period is made. Species included in the analysis were southern blue whiting (Micromesistius australis), patagonian hoki (Macruronus magellanicus), patagonian toothfish (Dissostichus eleginoides), red cod (Salilota australis), southern hake (Merluccius australis) and ling (Genypterus blacodes). Annual and monthly catches, fishing grounds, number of vessels that participated in the fisheries, main landing ports and other characteristic of interest are presented. When it was necessary to correct official statistics, data bases were modified per fishing area and type of fleet using different catches differentiation criteria
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    Estimación de un índice de abundancia anual estandarizado para pescadilla de red (Cynoscion guatucupa), mediante la aplicación de un modelo lineal general; período 1992-2003
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Ruarte, Claudio; Perrotta, Ricardo G.
    The stripped weakfish (Cynoscion guatucupa) has a wide latitudinal distribution (22° S-43° S) and it is object of fishery in Brazil, Uruguay and Argentina (SW Atlantic). In this last country, it is mainly captured in the coastal region of Buenos Aires Province by means of a fleet, which has between 20 m and 30 m length. In Argentina, the average landings in the last 5 years were 9,900 t. It is the second commercial species among the coastal groups. There are two main fishery areas of this species: the Argentinean-Uruguayan Common Fishing Zone (AUCFZ) and the El Rincón area, in the South of bonaerense littoral. Due to the importance of this species, it is necessary to define an index of annual abundance to allow a suitable diagnosis of the fishery condition. The General Linear Model is a suitable model to calculate this index. The factors used in this work were: year, trimester, 4 length categories and 5 sub areas. All of them were significant and reflect spatial-temporal changes in the abundance of this species. The model explained 34% of the total variability in the AUCFZ and 46% in the El Rincón. In general, the trends of catch per unit effort (CPUE) were similar and increasing in both areas, registering a greater increase in the internal areas. On the other hand, the fleet displacements between the areas and the reduction of the total fishery area caused a rise in the annual CPUE and a fall of the captures. These captures were dominated by adults but with an important presence of juveniles in the coastal zone off Mar del Plata city.
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    Evaluación de merluza de cola (Macruronus magellanicus) en el Atlántico Sudoccidental. Período 1985-2001
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Wöhler, O.C.; Hansen, J.E.; Giussi, A.R.; Cordo, H.D.
    Period 1985-2001. A stock assessment of Patagonian hoki of the Southwest Atlantic was carried out by using data from the years 1985-2001. A cohort analysis, fitted with some survey abundance indices was used in an adaptive conceptual framework. Simulation trials were performed to project the evolution of the fishery, to evaluate the risk of over-fish the stock under different exploitation levels, and to estimate Biologically Acceptable Catches (BAC). Both total biomass and spawning stock biomass showed increasing trends resulting from four strong year classes (1993, 1995, 1996 and 1998). Total biomass at the beginning of 2001 was estimated to be 2.5 million tons, and spawning stock biomass at the spawning time (August) was estimated to be around 1.28 million tons. The exploitation rate was low (0.19) and showed a decreasing trend in relation to previous years. The fishing mortality rate producing sustainable total catches in the long term, i.e., BAC corresponded to yields between 160 and 306 thousand tons during 2002, depending on future levels of recruitment
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    Evaluación de polaca (Micromesistius australis) en el Atlántico Sudoccidental. Período 1987-2001
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Wöhler, O.C.; Hansen, J.E.; Cassia, M.C.; Cordo, H.D.
    Period 1987-2001. A diagnosis of the current state of Southern blue whiting (Micromesistius australis) stock in the Southwest Atlantic was carried out on the basis of catches corresponding to the period 1987-2001 as reported by the Argentine fleet and also by vessels operating around Malvinas Islands. Abundance and current fishing mortality rates were estimated, and the biomass evolution in the long term resulting from some possible exploitation strategies based on different management strategies were projected. A sequential population analysis calibrated under a conceptual adjustable framework with five independent abundance indices was carried out. The effects on the biomass estimates were analysed by adopting different selection patterns and calibration indices as well as taking into account the under-declaration and discard of catches. Results indicated that the declining trend of Southern Blue Whiting observed in previous studies has continued, but it has been less marked than in preceding years. Total biomass estimates at the beginning of 2001 ranged between 566 and 622 thousand tonnes, whether the under-reporting or discards of catches by the Argentine fleet were taken into account or not. Accordingly, the spawning biomass at the onset of spawning ranged between 403 and 442 thousand tonnes. These values would correspond to 27-29% of the virgin biomass. Current fishing mortality was estimated as 0.27, corresponding to a relatively high exploitation rate (0.56). Projections aimed at four possible management objectives showed that biologically acceptable catches would range 22-84 thousand tonnes in 2002. Catches in the Southwest Atlantic should not exceed 50 thousand tonnes during 2002 in order to stop the declining trend of Southern blue whiting biomass.
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    Evaluación del recurso abadejo y recomendaciones sobre su explotación a partir del año 2002
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Cordo, H.D.
    Ling (Genypterus blacodes) resource was assessed by means of an age structured production model fitted with stock abundance indices from catch per unit effort data (CPUE) obtained from the commercial fishing fleet. Reproductive stock was assessed in the same way with CPUE data from the fishery research vessel. A short-term analysis of collapse risk as a function of 1999 and 2000 fishing mortalities was carried out with the results, and also a long-term analysis with the assumption of a variable fishing mortality (F) with two recruitment hypotheses. Results show that the present state of the Ling resource has worsened with respect to the last assessment. Considering the best of all cases, the Br/Kr relationship decreased from 0.55 to 0.33, indicating that the reproductive stock is near the acceptable limit assumed in this paper. Risk analysis pointed out that catch should be kept at a level of 16,000 t year-1 in the long term to maintain collapse risk within acceptable levels ( 10%). This would imply decreasing total allowable catch levels, currently at 19,000 t year-1. Nevertheless, since Ling is in great proportion, a by-catch of the common hake fishery, catch levels are regulated to a great extent by the effort directed to hake. In addition, it was observed that Ling catch by longliners increased from 137 t in 1998 to 3.088 t in 2001. This implies an increase in fishing effort oriented to Ling. From the above discussion it is inferred as necessary to limit fishing effort oriented to Ling particularly that exerted during the first quarter of the year around the reproductive area. Based on results from this and other reports, some proposals for management of the species starting from the year 2002 are indicated.
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    Muestreo 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.
    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.
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    Observaciones sobre el comportamiento de la merluza (Merluccius hubbsi) durante la pesca de arrastre
    (Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), 2007) Casarsa, L.; Madirolas, A.
    The normal behavioral patterns of several fish species is altered during trawling affecting the fish spatial distribution. Sonar methods were carried out in this research work in order to study the reaction of reproductive concentrations of the Argentine hake (Merluccius hubbsi) during mid-water and bottom fishing trawls. Observations made from a trawl sonar mounted on the headrope of an ENGEL (35 m) bottom trawl, showed that this species concentrates at the lower-central sector of the net mouth. During daytime trawls fish schools with a vertical distribution exceeding ten meters were observed entering the trawl within the first two meters from the bottom. Some observations during pelagic trawls carried out at night, showed no specific pattern at the net mouth. The observational method was efficient when fish densities were higher than 66,662 fish per nautical mile2, although it may only be considered as representative of the survey conditions, that is to say summer spawning concentrations of Argentine hake.