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  • 1
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sagittal otoliths were used for age determination in 1121 specimens of Micromesistius australis, caught in waters of the South-West Atlantic during the cruises made by the ships Walther Herwig and Shinkai Maru in agreement with the Argentine Republic, during the years 1978 and 1978/1979, respectively. The interpretation of growth rings required the otoliths to undergo a paraffin wax embedding and cutting technique. The relations otolith length-fish length and fish length-half otolith width were linear. Thus, back calculations, when necessary, were made by a simple extrapolation. Numbers of males and females were nearly equal, resulting in a sex ratio of 1:1.09. Length frequencies and age distributions were calculated for each sex separately. A significant difference in growth between sexes was found, curves for each were derived. A linear, regression was made and the Von Bertalanffy equation estimated as: Lt=56.90 [1-e-0.1983 (t+1.84)], in males, and Lt=60.08 [1-e-0.1769 (t+2.07)] in females, with Lt in cm and t in years. For estimation of these equation parameters age groups 2–16 years in males and 2–22 years in females were taken into account. All theoretical Lt values and almost all observed lengths for females were greater than those of males in corresponding age groups. Previously published observations about M. australis on this subject, are not in agreement or only in partial accord with present results. These are discussed. Original photographs of otolith cross sections illustrating age determination methods are presented for the first time in age and growth studies of this species.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Approximately 1000 specimens belonging to eight fish species were collected at Potter Cove, King George Island, South Shetland Islands, from August 1985 to May 1986. This study deals with the dominant species Notothenia neglecta, Notothenia gibberifrons, Trematomus newnesi and Notothenia rossii marmorata. Age and size structure of the fish were analyzed using scale and otolith readings. Notothenia neglecta was the most abundant species. It spawns in the austral autumn. Juvenile N. rossii marmorata migrate offshore when sexually mature. Over eight hundred stomach contents were analyzed. The four species studied were generally benthophagous. However, in summer T. newnesi and N. rossii marmorata, carried out vertical migrations, feeding on pelagic organisms. Gammarid amphipods constituted the main food in all four species. Algae were consumed regularly throughout the year and we suggest that they are intentially eaten by the fish, rather than by accident. Two 48 hour sampling periods, carried out in summer of 1987, showed that N. neglecta was more active during the day.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Polar biology 18 (1997), S. 219-222 
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The analysis of 29 stomach contents collected from a colony close to Pirie Peninsula, South Orkney Islands, from 2 January to 18 February 1995, showed that fish were by far the most important prey of the Antarctic shag Phalacrocorax bransfieldensis, followed by octopods, decapods and gammarids. The fish Notothenia coriiceps constituted the bulk of the diet; however, its importance decreased by the end of the study when Lepidonotothen nudifrons was the most important prey. The composition of the stomach contents varied throughout the breeding season according to changes in the chicks' energetic demands; as chicks grew older the adults increased the mass of the loads carried to the nests, preying on larger fish, a phenomenon also observed at the South Shetland Islands.
    Materialart: Digitale Medien
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  • 4
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    Unbekannt
    In:  EPIC3Reports on polar and marine research, 299, pp. 258-262
    Publikationsdatum: 2019-07-16
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , peerRev
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  • 5
    Publikationsdatum: 2019-07-16
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
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  • 6
    facet.materialart.
    Unbekannt
    Mar del Plata: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP)
    Publikationsdatum: 2021-05-19
    Beschreibung: The diet composition of the icefish Champsocephalus gunnari caught around the South Georgia Islands and Shag Rocks, Atlantic sector of Antacrtica in February/March 1994 was analyzed using the frequency of occurrence (. ) method. Krill Euphausia superba followed by the hyperiid amphipod Themisto gaudichaudii were the main prey items at South Georgia and Shag Rocks; first were found in thestomachs more frequently than in past seasons around South Georgia,in parallel with the virtual absence of mysids and Thysanoessaspp. Krill was available for fish at the same level than in previous years (e.g. 1985, 1992). However, high proportion of empty stomachs were found at South Georgia and Shag Rocks, close to the values reported for the 1991 year of krill 'shortage'. Besides, the tentative analysis of part of the samples using coefficient Q (. )showed a greater importance of T.gaudichaudii with respect to krill.It is possible that the inconsistencies found between the results obtained by both methods are due to a particular spatial distribution of krill in the area in the period of study, but no previous data are available for comparison. No krill aggregations were found in the region by acoustic methods in the 1994 summer season; a fact that might be related to a significant change in surface temperature observed during the cruise.
    Beschreibung: Publisher permission
    Beschreibung: Published
    Beschreibung: Channichthyidae, Champsocephalus gunnari, Pez de hielo, relevamientos pesqueros, contenido estomacal, alimentación, preferencias alimenticias
    Schlagwort(e): Feeding ; Food preferences ; Feeding ; Food preferences ; Stomach content ; Fishery surveys
    Repository-Name: AquaDocs
    Materialart: Journal Contribution
    Standort Signatur Einschränkungen Verfügbarkeit
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