Browsing by Author "OYARZUN, C"
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- ItemFEEDING ECOLOGY OF THE SOUTH-AMERICAN SEA LION OTARIA-FLAVESCENS - FOOD CONTENTS AND FOOD SELECTIVITY(1985) GEORGENASCIMENTO, M; BUSTAMANTE, R; OYARZUN, CWhile predation by pinnipeds is likely to be important in shaping the structure of marine communities, there are few reports from the southeastern Pacific Ocean where pinniped populations are abundant and a massive fishing industry has developed in recent years. The food contents of 29 South American sea lions Otaria flavescens Shaw, 1800 and quantitative information on the occurrence of prey taxa are reported by frequency and mass. Estimates of the relative abundance of prey taxa in the environment, daily and annual food consumption rates, and sea lions'' food selectivity are given. Sea lions tend to consume slow swimming, bentho-demersal fish species, rather than the more abundant pelagic fish species in the study area. The jack mackerel Trachurus murphyi (Nichols) was the most frequent prey item found in the alimentary tracts and in the environment, but it was not preferred nor was it an important contributor of biomass to the diet. The non-commericial hake Macruronus magellanicus (Lonnberg) was the most preferred and the most important by mass in the diet. Estimated annual consumption of cusk eels (Genypterus spp.) revealed that sea lions took .apprx. 7 times more fish in mass than those annually landed in the study area. Unfortunately, estimates of standing stocks of standing stocks for the different prey taxa consumed by the sea lions are not yet available, and so the magnitude of their impact on fisheries is difficult to evaluate.
- ItemSOME CHARACTERISTICS OF MACROBENTHIC FAUNA FROM THE ORGANIC-ENRICHED SEDIMENTS AT TALCAHUANO, CHILE(1987) OYARZUN, C; CARRASCO, FD; GALLARDO, VAThe community structure of the macrobenthic (> 500 .mu.m) fauna from organic matter enriched-soft bottom of Talcahuano Port, Concepcion Bay, Chile, was studied and compared over other two sites located further away with progressively less organic content. Polychaeta was the main taxon reaching 93.7% of the whole analyzed fauna. The numerical abundances were high (from 26.280 ind. m-2 to 63.830 ind. m-2), while the number of species was low (44 species). The species diversity values calculated for the fauna were low, and the same pattern for the evenness was observed. The Talcahuano port benthic station (C1) was dominated by the great numbers of the small opportunistic spinoid polychaete Carraziella carrascoi. The nearby station C2 showed high numbers of the small polychaete Cossura chilensis and oligochaetes. The more distant site from Talcahuano port (station C3) was dominated by individuals of C. carrascoi and Owenia collaris. The stations (C1 and C2) more associated with Talcahuano port facilities, where the organic matter was important, exhibited the highest number of individuals and the lowest amount of species, which was reflected in low species diversity figures and the low slopes of the rarefaction curves. The macrobenthic fauna of station C1 (Talcahuano port) and C2, conformed a different faunal assemblage with respect to station C3, as was showed by the numerical classification. The log-normal distribution analysis of individuals among species showed a faunal transition phase to organic pollution for the two more Talcahuano port associated benthic stations.
- ItemTHERMO-LUMINESCENCE IN PLASTICALLY DEFORMED AND IRRADIATED KBR SINGLE-CRYSTALS(1987) MARIANI, DF; BRITO, F; OYARZUN, C; VIGNOLO, J