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  • 1
    Publication Date: 2021-05-19
    Description: In August 1996 acoustic methods were employed to estimate mackerel (Scomber japonicus) abundance in the Buenos Aires, Argentina shelf area of "El Rincón" (4,287 mn2), located between 39°- 40° 30' S. Results showed a biomass estimate of 77,260 t. ASIMRAD EK-500 equipment operated with a 38 KHz split-beam transducer was used. Midwater fishing trawls were employed to identify echotraces and to collect mackerel samples.Trawls 4 and 5 were the most successful. Samples included only adult fish (310-470 mm Lt and ages ranging 2-11). Length and weight growth parameters and mortality rates were estimated. Analysis of the stomach contents revealed that mackerel was feeding exclusively on zooplankters over 2 mmlength. The analysis of the characteristics (dimensions and density) of the mackerel shoals allowed to detect two areas of concentration above and below 40°S latitude. The northern area was characterized by relatively small schools of medium density similar to those of the Mar del Plata area. In the southern zone, large schools of high density that account for almost 92 of the total biomass were found.Differences between both areas were also detected when plankton distribution was analyzed. Higher abundances of the dinoflagellate Alexandrium tamarense corresponded to the southern area. On the contrary, higher zooplankton biomass was detected northerly of 40°S. From an oceanographic standpoint, the presence of mackerel was associated to relatively higher salinity values. As a result of the different data analyzed it is suggested that,during this time of the year, the species shows a migratory pattern from the intermediate shelf to coastal areas.
    Description: Publisher permission
    Description: Published
    Description: Scombridae, Scomber japonicus, caballa, zooplancton, relevamientos ecoicos, condiciones ambientales, biomasa, abundancia, estructura poblacional
    Keywords: Biomass ; Population structure ; Zooplankton ; Environmental conditions ; Abundance ; Biomass ; Population structure ; Zooplankton ; Environmental conditions ; Echo surveys
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 2
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    Unknown
    Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP)
    Publication Date: 2021-05-19
    Description: Lagrangian changes in distribution and survival within an anchovy egg and larvae patch were studied by means of multiple opening/closing sampling following a free drifting buoy. The buoy was equipped with a radar reflector and flashing light, and it was connected to a current cross drogue floating at 15 m depth, which corresponded to the main egg and larvae concentration within the patch. The drifter was launched on the Buenos Aires continental shelf, off Necochea during the spring spawning peak of 1983. Three discrete depths (within, below and above the thermocline)were repeatedly sampled close to the drogue with a Motoda sampler. Egg and larval abundances in the vicinity of the drogue were monitored at 3/4 hour intervals for a period of three days. Each plankton station included a set of hydrographic and climatological data registered simultaneously. The efficiency of the drogue as a Lagrangian marker was examined by means of the application of multifactorial ANOVA to test the significance of variability between days, light regime, sampling depths, population structure and their interactions. Wind drag on the surface unit did not significantly affect the trajectory of the drogue. Patterns of embryonic and larval vertical distribution are discussed by means of the variations in the centre of mass, in the vertical dispersion and patchiness indexes for each developmental stage analyzed. There is evidence of diel vertical migration in larvae larger than 8 mm SL. Although the incidence of feeding based on observations of the presence of undigested food in the gut content of larvae was low, a daily feeding pattern over a 14-hour period starting after sunrise, was evident. Evening ascent of larger larvae was not related to feeding activity. A single equation two-stage model, assuming age dependent mortality in the embryonic and post-larval period is derived and compared to standard models based on constant exponential decay during each developmental phase.
    Description: Publisher permission
    Description: Published
    Description: Engraulidae, Engraulis anchoita, anchoíta, relevamientos ictioplanctónicos, relevamientos pesqueros, larvas de peces, huevos de peces, distribución vertical, abundancia, boyas a la deriva, efectos ambientales, alimentación, supervivencia, migraciones verticales
    Keywords: Feeding ; Fish larvae ; Survival ; Fish larvae ; Fish eggs ; Vertical migrations ; Feeding ; Environmental effects ; Ichthyoplankton surveys ; Vertical distribution ; Survival ; Abundance ; Drifting data buoys ; Fishery surveys
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 3
    Publication Date: 2021-05-19
    Description: This paper reviews the information on pelagic and demersal fish eggs and larvae, describing the distribution and seasonality of different species and their arrangement in icthyoplankton assemblages in the Southern patagonian waters. It also reports on 11 surveys conducted by INIDEP during 1992-1995. A total of 488 ichthyoplankton samples were analyzed. Fish eggs have been recognized in 47. of all ichthyoplankton samples. They belong to three species: Coelorhynchus fasciatus, Macrourus whitsoni and Micromesistius australis. Fish larvae of 23 species and 17 families have been identified in 96. of all samples analyzed. Spawning of most species begins in autumn, and progresses through winter, when the southern blue whiting and grenadier fish contribute to more than half of all eggs present in our samples. Nototheniid and myctophiid larvae were caught during all year long. Four larval groups were detected using cluster analysis: the first group, formed exclusively by nototheniids, which occupied a vast area on the continental shelf between 100 and 200 m depth, the second formed by Agonopsis chiloensis, Eleginops maclovinus, Macruronus magellanicus and Sprattus fuegensis in coastal waters, the third formed by myctophiids, Gymnoscopelus spp. and Micromesistius australis, inhabit the outer continental shelf and slope, and the fourth included Protomyctophum spp., Krefftichthys anderssoni and Bathylagus antarcticus, species typically found in Subantarctic waters of the Malvinas Current. Comparing the distribution of eggs and larvae of blue whiting from collections obtained during the 70's and 80's, with those of recent surveys, it is evident, that a significant contraction of the spawning grounds of the species has take place, particularly to the west of the archipelago.
    Description: Sánchez, R.P.; ed. 1999. Reproductive habitat, biology and acoustic biomass estiomates of the southern blue whiting (Micromesistius australis) in the sea off southern patagonia. INIDEP Documento Científico, 5: 93 p.
    Description: Published
    Description: larvas de peces, huevos de peces, distribución estacional, abundancia de asociaciones, ictioplancton
    Keywords: Fish larvae ; Ichthyoplankton ; Fish larvae ; Fish eggs ; Seasonal distribution ; Abundance
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 4
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    Unknown
    Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero
    Publication Date: 2021-05-19
    Description: Data considered in this paper were obtained during a research cruise carried out on board of RV Dr. E.L. Holmberg from INIDEP (Instituto Nacional de Investigacion y Desarrollo Pesquero) during March-April 2000 in the area between 48°S and 55°S (S Patagonian) region, SW Atlantic. From 61 bottom trawls a total of 355 specimen belonging to 11 skate species were collected. This represents, in number, 1.8 of the total species biomass. All skate species were identified and some biological characteristics for each species analyzed. Abundance was estimated in tons and the distribution area of each species was determined. Total weight and morphometric data by sex were measured total length, disc width and clasper length. Stomach content and macroscopical reproductive conditions were checked in every individual gonads, epididymis, alar thorns, yolk oocytes, oviductal gland and eggs. The most abundant species were: Dipturus chilensis, Bathyraja macloviana, Psammobatis normani, Psammobatis rudis, and Bathyraja magellanica distributed in the whole study area. In lesser abundance Bathyraja brachyurops and Bathyraja albomaculata were present south of 51°S. The other skate species were occasional, with percentages of appearance lower than 1 Amblyraja doellojuradoi, Bathyraja griseocauda, Bathyraja multispinis and Sympterygia bonapartii. Food items in the stomach were identified and cluster analysis was used to characterize feeding preferences. Species were grouped according to feeding habits such as anelidophagous (P.normani, B.macloviana and B.albomaculata), mainly piscivorous (D.chilensis, B.griseocauda and B.brachiurops and to carcinophagous habits P.rudis, B.magellanica, A.doellojuradoi, B.multispinis and S.bonapartii.
    Description: Publisher permission
    Description: Published
    Description: Rajidae, rayas
    Keywords: Feeding behaviour ; Marine fish ; Abundance ; Stomach content ; Food organisms ; Diets ; Feeding behaviour ; Community composition
    Repository Name: AquaDocs
    Type: Journal Contribution
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