Slow recovery of previously depleted demersal fish at the South Shetland Islands, 1983-2010

Following seals and baleen whales prior to the 1970s, demersal fish stocks were depleted off the South Shetland Islands by intensive industrial fishing during the late 1970s to early 1980s. Little has been reported since about how these stocks have fared, after international agreement closed this fishery in 1990. We report changes in size and abundance of the commercially exploited Notothenia rossii and Gobionotothen gibberifrons relative to the ecologically similar but unexploited Notothenia coriiceps at Potter Cove, South Shetland Islands, over a 28-yr period, 1983?2010. N. rossii abundance declined from 1983 to 1991, and an increase in mean size during 1983?1984 is consistent with weak cohorts during preceding years. Modal age changed from 2?3 to 6?7 yr. Length data of G. gibberifrons, available from 1986, exhibited a similar pattern, showing a decrease until 1991?1992. After a period of relative stability (1992?1994), a sharp increase in length and a continued decline in relative abundance indicated low recruitment. The length?frequency distribution of unexploited N. coriiceps throughout the whole period showed no change in modal size or mean length of the fish. We relate these patterns to the fishery and suggest that a further two decades will lapse before these stocks recover. Using the South Shetland fisheries as an example, current management rules for Southern Ocean fisheries, deemed to be precautionary and disallowing depletion beyond which a stock can recover in 2?3 decades, may be unrealistic in an ocean profoundly altered by numerous stock depletions and rapid climate change.Fil: Marschoff, Enrique Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Barrera Oro, Esteban. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alescio, Nadia Soledad. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ainley, David G.. No especifíca

Receptor protein tyrosine phosphatases control Purkinje neuron firing

Spinocerebellar ataxias (SCA) are a genetically heterogeneous family of cerebellar neurodegenerative diseases characterized by abnormal firing of Purkinje neurons and degeneration. We recently demonstrated the slowed firing rates seen in several SCAs share a common etiology of hyper-activation of the Src family of non-receptor tyrosine kinases (SFKs). However, the lack of clinically available neuroactive SFK inhibitors lead us to investigate alternative mechanisms to modulate SFK activity. Previous studies demonstrate that SFK activity can be enhanced by the removal of inhibitory phospho-marks by receptor-protein-tyrosine phosphatases (RPTPs). In this Extra View we show that MTSS1 inhibits SFK activity through the binding and inhibition of a subset of the RPTP family members, and lowering RPTP activity in cerebellar slices with peptide inhibitors increases the suppressed Purkinje neuron basal firing rates seen in two different SCA models. Together these results identify RPTPs as novel effectors of Purkinje neuron basal firing, extending the MTSS1/SFK regulatory circuit we previously described and expanding the therapeutic targets for SCA patients

Colony size and foraging range in seabirds

The reasons for variation in group size among animal species remain poorly understood. Using ‘Ashmole's halo’ hypothesis of food depletion around colonies, we predict that foraging range imposes a ceiling on the maximum colony size of seabird species. We tested this with a phylogenetic comparative study of 43 species of seabirds (28 262 colonies), and investigated the interspecific correlation between colony size and foraging ranges. Foraging range showed weak relationships with the low percentiles of colony size of species, but the strength of the association increased for larger percentiles, peaking at the maximum colony sizes. To model constraints on the functional relationship between the focal traits, we applied a quantile regression based on maximum colony size. This showed that foraging range imposes a constraint to species’ maximum colony sizes with a slope around 2. This second-order relationship is expected from the equation of the area of a circle. Thus, our large dataset and innovative statistical approach shows that foraging range imposes a ceiling on seabird colony sizes, providing strong support to the hypothesis that food availability is an important regulator of seabird populations.Peer Reviewe

Parental body condition does not correlate with offspring sex-ratio in Cory's shearwater

We analyzed offspring sex ratio variation in Mediterranean Cory's Shearwater (Calonectris d. diomedea) during two consecutive breeding seasons in two colonies. We test for differential breeding conditions between years and colonies looking at several breeding parameters and parental condition. We then explored the relationship between offspring sex ratio and parental condition and breeding parameters. This species is sexually dimorphic with males larger and heavier than females; consequently we expected differential parental cost in rearing sexes, or a greater sensitivity of male chicks to adverse conditions, which may lead to biased sex ratios. Chicks were sexed molecularly by the amplification of the CHD genes. Offspring sex ratio did not differ from parity, either at hatching or fledging, regardless of the colony or year. However, parental body condition and breeding parameters such as egg size and breeding success were different between years and colonies. Nevertheless, neither nestling mortality nor body condition at fledging varied between years or colonies, suggesting that male and female chicks were probably not differentially affected by variability in breeding conditions

The dynamics of cultivation and floods in arable lands of Central Argentina

Although floods in watersheds have been associated with land-use change since ancient times, the dynamics of flooding is still incompletely understood. In this paper we explored the relations between rainfall, groundwater level, and cultivation to explain the dynamics of floods in the extremely flat and valuable arable lands of the Quinto river watershed, in central Argentina. The analysis involved an area of 12.4 million hectare during a 26-year period (1978–2003), which comprised two extensive flooding episodes in 1983–1988 and 1996–2003. Supported by information from surveys as well as field and remote sensing measurements, we explored the correlation among precipitation, groundwater levels, flooded area and land use. Flood extension was associated to the dynamics of groundwater level. While no correlation with rainfall was recorded in lowlands, a significant correlation (<i>P</i><0.01) between groundwater and rainfall in highlands was found when estimations comprise a time lag of one year. Correlations between groundwater level and flood extension were positive in all cases, but while highly significant relations (<i>P</i><0.01) were found in highlands, non significant relations (<i>P</i>>0.05) predominate in lowlands. Our analysis supports the existence of a cyclic mechanism driven by the reciprocal influence between cultivation and groundwater in highlands. This cycle would involve the following stages: (a) cultivation boosts the elevation of groundwater levels through decreased evapotranspiration; (b) as groundwater level rises, floods spread causing a decline of land cultivation; (c) flooding propitiates higher evapotranspiration favouring its own retraction; (d) cultivation expands again following the retreat of floods. Thus, cultivation would trigger a destabilizing feedback self affecting future cultivation in the highlands. It is unlikely that such sequence can work in lowlands. The results suggest that rather than responding directly and solely to the same mechanism, floods in lowlands may be the combined result of various factors like local rainfall, groundwater level fluctuations, surface and subsurface lateral flow, and water-body interlinking. Although the hypothetical mechanisms proposed here require additional understanding efforts, they suggest a promising avenue of environmental management in which cultivation could be steered in the region to smooth the undesirable impacts of floods

Acetonitrile­trichloridobis(cyclo­hexyl­diphenyl­phosphane)rhodium(III) acetonitrile disolvate

In the title compound, [RhCl3(CH3CN)(C18H21P)2]·2CH3CN, the complex mol­ecule lies on a twofold rotation axis that passes through the RhIII atom, one Cl atom, and the C and N atoms of the coordinated acetonitrile mol­ecule. The RhIII atom is coordinated by two P atoms in trans positions, three Cl atoms and an acetonitrile mol­ecule in a distorted octa­hedral geometry. Intra­molecular C—H⋯Cl inter­actions are observed. The uncoordinated acetonitrile mol­ecule is disordered over two sites with occupancies of 0.588 (4) and 0.412 (4)

Synthesis of oxazolidinones in supercritical CO2 under heterogeneous catalysis

Basic alumina efficiently promotes the reaction of propargylamines with scCO2 for the synthesis of variously substituted oxazolidinones that, after catalyst filtration, are easily isolated by methanol crystallization

Use of the Richtmyer-Meshkov Instability to Infer Yield Stress at High-Energy Densities

We use the Richtmyer-Meshkov instability (RMI) at a metal-gas interface to infer the metal’s yield stress (Y) under shock loading and release. We first model how Y stabilizes the RMI using hydrodynamics simulations with a perfectly plastic constitutive relation for copper (Cu). The model is then tested with molecular dynamics (MD) of crystalline Cu by comparing the inferred Y from RMI simulations with direct stress-strain calculations, both with MD at the same conditions. Finally, new RMI experiments with solid Cu validate our simulation-based model and infer Y~0.47 GPa for a 36 GPa shock

Are white storks addicted to junk food? Impacts of landfill use on the movement and behaviour of resident white storks (Ciconia ciconia) from a partially migratory population

Background: The migratory patterns of animals are changing in response to global environmental change with many species forming resident populations in areas where they were once migratory. The white stork (Ciconia ciconia) was wholly migratory in Europe but recently guaranteed, year-round food from landfill sites has facilitated the establishment of resident populations in Iberia. In this study 17 resident white storks were fitted with GPS/GSM data loggers (including accelerometer) and tracked for 9.1 ± 3.7 months to quantify the extent and consistency of landfill attendance by individuals during the non-breeding and breeding seasons and to assess the influence of landfill use on daily distances travelled, percentage of GPS fixes spent foraging and non-landfill foraging ranges. Results: Resident white storks used landfill more during non-breeding (20.1 % ± 2.3 of foraging GPS fixes) than during breeding (14.9 % ± 2.2). Landfill attendance declined with increasing distance between nest and landfill in both seasons. During non-breeding a large percentage of GPS fixes occurred on the nest throughout the day (27 % ± 3.0 of fixes) in the majority of tagged storks. This study provides first confirmation of year-round nest use by resident white storks. The percentage of GPS fixes on the nest was not influenced by the distance between nest and the landfill site. Storks travelled up to 48.2 km to visit landfills during non-breeding and a maximum of 28.1 km during breeding, notably further than previous estimates. Storks nesting close to landfill sites used landfill more and had smaller foraging ranges in non-landfill habitat indicating higher reliance on landfill. The majority of non-landfill foraging occurred around the nest and long distance trips were made specifically to visit landfill. Conclusions: The continuous availability of food resources on landfill has facilitated year-round nest use in white storks and is influencing their home ranges and movement behaviour. White storks rely on landfill sites for foraging especially during the non-breeding season when other food resources are scarcer and this artificial food supplementation probably facilitated the establishment of resident populations. The closure of landfills, as required by EU Landfill Directives, will likely cause dramatic impacts on white stork populations