Pejerrey is an important zooplanktivorous native ¢sh of the Argentinean inland waters. It has been traditionally propagated for stocking purposes by relatively costly semi-intensive and intensive methods. In this study, we evaluated the implementation of an extensive culture method by using £oating cages in a shallow pampean lake. Four cages were installed in the Lacombe Lake and stocked with juveniles (16.24 AE 1.69 mm length) at 50 ¢sh m À 3 density for growing until the size of 150 mm, which is considered as a suitable size for stocking. Throughout the experiment, the temperature ranged between 10 and 26 1C and the zooplankton biomass ranged between 12 and 3269 mg dw L À 1 . The growth patterns in the length were similar in the four cages and directly related to the lake thermal conditions and zooplankton availability. The average ¢nal length after 315 days was 154.4 AE 8.8 mm. The survival rates ranged between 53.5% and 64.7% during the ¢rst 110 days and 11.1^25.7% at termination. Growth rate for the ¢rst 2 months was the highest documented for pejerrey culture. This simple technique o¡ers the possibility to produce juvenile pejerrey at a low cost and provides the alternative of reinforcing the natural populations with ¢sh already adapted to the natural environmental conditions. Aquaculture Research, 2010, 41, e376^e384 Floating cage culture of pejerrey in pampean lakes D C Colautti et al.

Pampean lakes are characterised by the alternation of flood and drought periods, but little is known about its effects on fish assemblage in an extended temporal scale. This study analyses the temporal variability of the fish assemblage in Chascomús Lake, and discusses the role of temperature and precipitation as potential drivers of fish composition shifts. Data acquisition was based on experimental fishing performed from 1999 to 2013 and from historical fishing records. Two alternative fish assemblage configurations were identified by cluster analysis. Odontesthes bonariensis, Parapimelodus valenciennisand Cyphocharax voga were the dominant species, which accounted for 70-80% of the relative abundance. The species O. bonariensis showed temporal fluctuations in its representativeness, changing from dominant to almost absent, whereas C. voga and P. valenciennis changed their abundance following a similar pattern along time. When historical data were considered, Platanichthys platana appeared as the fourth most relevant species. Precipitation, critical temperatures and fish mortalities were identified as the main drivers of species abundance shifts. This study highlights the importance of long-term assessments to understand the influence of climatic factors and the need to maintain or restore natural ecological processes as the basis to support dynamic sustainable fisheries in Pampean shallow lakes.

The diet of non-breeding male Antarctic fur seals, Arctocephalus gazella, was investigated at Stranger Point, King George Island, through the analysis of scats during three consecutive summer seasons (1996, 1997, 1998). Overall, Wsh and krill were the most frequent prey occurring, respectively, in an average of 82.9% and 78.8% of samples (n = 131), followed by penguins (22.8%) and cephalopods (17.8%). Myctophids constituted almost 90% of the Wsh predated, with Electrona antarctica and Gymnoscopelus nicholsi being the most abundant and frequent species consumed. All Wsh taxa identiWed were krill feeding species suggesting that seals foraged mainly on a krill and a Wsh community associated with krill aggregations. However, a seasonal change was observed in the relative proportions of the diVerent prey taxa, with a progressive decrease with time in the occurrence of krill and a concomitant increase of Wsh, penguins and squid. Possible inXuence of the strong 1997/98 ENSO event is discussed.