Extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow pampean lake in Argentina

Pejerrey is an important zooplanktivorous native fish 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 floating cages in a shallow pampean lake. Four cages were installed in the Lacombe Lake and stocked with juveniles (16.24 ± 1.69 mm length) at 50 fish m^?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 °C and the zooplankton biomass ranged between 12 and 3269 μg dw L^?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 final length after 315 days was 154.4 ± 8.8 mm. The survival rates ranged between 53.5% and 64.7% during the first 110 days and 11.1–25.7% at termination. Growth rate for the first 2 months was the highest documented for pejerrey culture. This simple technique offers the possibility to produce juvenile pejerrey at a low cost and provides the alternative of reinforcing the natural populations with fish already adapted to the natural environmental conditions.     

Winter intrusions of the loop current

Sea-surface temperature data obtained from satellite and subsurface temperature data obtained from ships are used to determine the intrusion of the The Loop Current extended considerably farther to the north during the last three winters than has been observed previously.     

Agroforestry for healthy ecosystems: constraints,improvement strategies and extension in Pakistan

Agroforestry Systems - Globally, forest ecosystems are shrinking and their health is declining due to a range of biotic and abiotic factors. Forest ecosystems in Pakistan...     

Hydrolytic stability of PLA yarns during textile wet processing

PLA knitted fabric was subjected to various textile wet processes viz., scouring, bleaching, and simulated dyeing. Various process parameters viz., temperature, time, and pH of the chemical bath were studied to investigate their effect on the hydrolytic stability of PLA fibers. The hydrolytic stability was measured in terms of weight loss and mechanical properties of PLA yarns. Infrared spectroscopy was carried out to investigate the surface chemistry of greige and processed PLA fibers. SEM was employed to investigate the surface morphology of fibers. The results showed that scouring should be carried out around glass transition temperature (T _g ) of the PLA polymer. Bleaching with hydrogen peroxide proved to be very deleterious to the fiber structure. Simulated dyeing of PLA at higher temperature and longer process times severely degraded the mechanical properties of PLA yarns.     

Evaluation of multi-satellite precipitation products for soil loss and sediment export modeling over eastern regions of the Koshi River Basin,Nepal

Journal of Soils and Sediments - Precipitation data are an important input variable for soil loss (SL) and sediment export (SE) modeling, although they are rarely available at fine spatial and...     

Molecular detection and characterization of ovine herpesvirus-2 using heminested PCR in Pakistan

BackgroundMalignant catarrhal fever (MCF) is a highly fatal lymphoproliferative disease of cattle, deer, bison, water buffalo, and pigs caused by the gamma-herpesviruses alcelaphine herpesvirus-1 (AlHV-1) and ovine herpesvirus-2 (OvHV-2).ObjectivesThis study aimed to determine the prevalence of OvHV-2 in sheep, goats, cattle, and buffalo in Rawalpindi and Islamabad, Pakistan, by applying molecular and phylogenetic methods.MethodsBlood samples were aspirated from sheep (n = 54), goat (n = 50), cattle (n = 46) and buffalo (n= 50) at a slaughterhouse and several farms. The samples were subjected to heminested polymerase chain reaction (PCR), followed by sequencing and phylogenetic analysis of the OvHV-2 POL gene and the OvHV-2 ORF75 tegument protein gene.ResultsThe highest percentage of MCF positive samples was in sheep (13%), whereas goat, cattle, and buffalo had lower positive percentages, 11%, 9%, and 6.5%, respectively. Four OvHV-2-positive PCR products obtained from sheep samples were sequenced. The sequences obtained were submitted to the NCBI GenBank database ({"type":"entrez-nucleotide","attrs":{"text":"MK852173","term_id":"1694854431","term_text":"MK852173"}}MK852173 for the POL gene; {"type":"entrez-nucleotide","attrs":{"text":"MK840962","term_id":"1686143390","term_text":"MK840962"}}MK840962, {"type":"entrez-nucleotide","attrs":{"text":"MK852171","term_id":"1694854427","term_text":"MK852171"}}MK852171, and {"type":"entrez-nucleotide","attrs":{"text":"MK852172","term_id":"1694854429","term_text":"MK852172"}}MK852172 for the ORF75 tegument protein gene). Phylogenetic analysis revealed a close similarity of study sequences with those of worldwide samples.ConclusionsThis study is the first cross-sectional study on the prevalence and molecular detection of OvHV-2 in apparently healthy cattle and buffalo that could be carrying OvHV-2 acquired from OvHV-2-positive sheep and goats. The results indicate that OvHV-2 is circulating in Pakistan. Further studies are needed to characterize OvHV-2 and elucidate further its prevalence.     

Effects of stocking density and natural food availability on the extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow Pampean lake in Argentina

An experiment was conducted for 80 days at La Salada de Monasterio Lake (Buenos Aires, Argentina) to assess the effect of stocking density and natural food availability on the growth and production of zooplanktivorous juveniles of pejerrey (Odontesthes bonariensis) in extensive cage culture. Ten cages were installed and stocked with 33‐day‐old fish, at three density treatments: 25, 50 and 75 ind. m^?3. Zooplankton was analysed in terms of abundance, biomass and diversity considering three size classes. Caged pejerrey diet was assessed regularly. The pejerrey gut contents composition was clearly different from cage zooplankton, showing a trend to contain bigger components. Reared fish exhibited a tendency to diversification of the diet and to change the mean prey size depending on fish length and stocking density. Regression models showed a positive and direct effect of the bigger zooplankton biomass on fish growth rates, which were also inversely affected by the availability of smaller zooplankton. The results demonstrate that stocking density and available zooplankton, in both quantity and quality, are key factors in regulating extensive cage culture of pejerrey. Handling stocking densities in a dynamic way it is possible to maximize fish growth, biomass harvest or fish number according to the goals of production.