The diet of Arctocephalus australis was studied through fecal analysis, from September of 1995 to May of 1998, in Isla de Lobos (35°01′50″S‐54°53′00″W), Uruguay. A total of 539 scats analyzed indicated that the weakfish (Cynoscion guatucupa), the cutlasfish (Trichiurus lepturus), the anchoveta (Engraulis anchoita), the anchovy (Anchoa marinii), and cephalopods were the main prey consumed by these fur seals. Prey richness was higher during January. The diet of A. australis varied between years, apparently related to changes in prey availability. C. guatucupa and E. anchoita decreased while T. lepturus and cephalopods increased from 1996 to 1998. South American fur seals fed on fish ranging in length from 5.4 to 104.8 cm and from 0.7 to 629.9 g in wet mass. However, the mean mass of the main items was never more than 200 g. Observations suggests that A. australis is a trophic generalist with the potential to prey on a wide range of species, although most of the diet is comprised of relatively few species. Fur seals and artisan fisheries both took C. guatucupa, with fur seals taking younger individuals (1–2 yr) than artisan fisheries (> 3 yr).
The jundia Ł (Rhamdia quelen) is a siluriform with great potential for aquaculture in South America. Fish oil is a raw material in diets for ¢sh. However, the ¢sheries that provide ¢sh oil have reached their limit of sustainability. Thus, the use of alternative sources for this ingredient is primordial. The aim of this study was to evaluate the performance and body composition of the jundia Ł fed with di¡erent sources of the vegetable oils. Jundia Ł (1.0 AE 0.2 g) were fed for 31 days with ¢ve isonitrogenous (37%) and isoenergetic (19 kJ g À1 ) diets, in which the following oils were added: 50 g kg À1 corn oil (CO), 50 g kg À1 ¢sh oil (FO), 50 g kg À1 linseed oil (LO), 33.4 g kg À1 ¢sh oil and16.7 g kg À1 linseed oil (1/3LO),16.7 g kg À1 ¢sh oil and 33.4 g kg À1 linseed oil (2/3LO). The performance did not show di¡erences between treatments. The ¢nal fatty acid pro¢le and n-3/n-6 ratio of the ¢sh were highly in£uenced by the diet. Fishfed diets with linseed and/or ¢sh oil showed superior n-3/n-6 ratios to the minimal recommended by the World Health Organization; whereas ¢sh fed diets with corn oil showed an inferior value. Albeit in the present study the commercial size of ¢sh was not attained, these results show a clear tendency. The desaturation/elongation capacity was evidenced, in this species, for the ¢rst time. Linseed oil can be utilized as a substitute for ¢sh oil in diets of jundia Ł without a¡ecting their performance and for producing goodquality ¢sh. However, more studies are necessary to con¢rm these results for commercial size. Performance of Jundia Ł fed on di¡erent dietary lipids R J Vargas et al. Aquaculture Research, 2008, 39, 657^665 r 2008 The Authors à AVIPAL, Porto Alegre, RS, Brazil. wIRGOVEL, Pelotas, RS, Brazil. zETNA, Canoas, RS, Brazil. ‰Giovelli Industria De Oleos Vegetais, Guaran|¤ das Misso ì es, RS, Brazil.zDigestible energy (kJ g -1 ) 5 (23.6 kJ g -1  %protein  0.9)1(39.8 kJ g -1  %lipid  0.85)1(17.2 kJ g -1  %carbohydrate  0.5) (Jobling 1983). kDigestible protein (DP) 5 0.9  %protein (Jobling 1983). HUFA, highly unsaturated fatty acid. Aquaculture Research, 2008, 39, 657^665 Performance of Jundia Ł fed on di¡erent dietary lipids R J Vargas et al. r 2008 The Authors Journal Compilation r 2008 Blackwell Publishing Ltd, Aquaculture Research, 39, 657^665 à Means (n 5 2) AE SD, with di¡erent letters in the same line are signi¢cantly di¡erent according to Tukey test (Po0.05). Only ¢sh of ¢nal treatments were including in the ANOVA. An SD 5 0.0 implies an SD of o0.05. wANOVA, one-way analysis of variance; CO, corn oil; FO, ¢sh oil; LO, linseed oil; SAT, saturated fatty acids; MUFAs, monounsaturated fatty acids; PUFAs, polyunsaturated fatty acids; HUFAs, highly unsaturated fatty acids. Aquaculture Research, 2008, 39, 657^665 Performance of Jundia Ł fed on di¡erent dietary lipids R J Vargas et al.
Essential fatty acids should be included in the diet to ensure adequate fish growth. Despite the great number of studies on fatty acid nutrition of fish, there are still several unknowns. The aim of the present study was to investigate fatty acid nutrition of jundi a, a Latin American freshwater catfish. Four diets were formulated containing (i) coconut oil (ÀC, negative control), (ii) coconut oil + high-docosahexaenoic-acid-fish oil (+C, positive control) and coconut + sunflower + linseed oils at different ratios, producing either (iii) a diet rich in linoleic acid (LA) (HighLA) or 4) a diet low in LA (LowLA). All diets contained significant amounts of saturated fatty acids (at least 57.5% total fatty acids in HighLA) and monounsaturated fatty acids (at least 19.1% total fatty acids in ÀC). Diets were fed to jundi a fingerlings (1.5 g) for 70 days; growth, body composition and liver histology were evaluated. The ÀC diet, without essential fatty acids, promoted significantly lower fish growth, body fat accumulation and hepatic lipidosis. Fish fed HighLA and LowLA diets presented similar growth as fish fed +C diet. These findings suggest that diet formulations for jundi a catfish fingerlings can include only plant oils without negative effect on growth, survival, body composition, fish health or parameters of feed utilization (ingestion rate and protein utilization).
The immune modulatory activity of diet long chain polyunsaturated fatty acids in fish has been previously demonstrated, although results for freshwater species are controversial. This study evaluates the effect of different dietary lipids on freshwater catfish jundiá, Rhamdia quelen, survival and its non-specific response (phagocytosis) after being inoculated with the pathogen Aeromonas hydrophila. Five diets were offered to jundiá fingerlings during 150 days prior to challenge: cod liver oil (FO), sunflower oil (SO), linseed oil (LO), canola oil (CO) and coconut oil (CNO). Accumulated mortality was significantly lower in fish fed FO and CNO diets and higher in fish fed LO. In spite of the highest values observed for phagocytotic activity in CNO-fed fish (50.0 + 12.7%) and in FO-fed fish (45.0 + 10.5%) when compared to those fed other diets, no significant differences in phagocytosis were reported. Results show the relevance of a balanced dietary lipid source with adequate concentrations of n-3 and n-6 series of fatty acids to prevent mortality after pathogen challenge.
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