Biology, Fishery, Conservation and Management of Indian Ocean Tuna Fisheries

The focus of the study is to explore the recent trend of the world tuna fishery with special reference to the Indian Ocean tuna fisheries and its conservation and sustainable management. In the Indian Ocean, tuna catches have increased rapidly from about 179959 t in 1980 to about 832246 t in 1995. They have continued to increase up to 2005; the catch that year was 1201465 t, forming about 26% of the world catch. Since 2006 onwards there has been a decline in the volume of catches and in 2008 the catch was only 913625 t. The Principal species caught in the Indian Ocean are skipjack and yellowfin. Western Indian Ocean contributed 78.2% and eastern Indian Ocean 21.8% of the total tuna production from the Indian Ocean. The Indian Ocean stock is currently overfished and IOTC has made some recommendations for management regulations aimed at sustaining the tuna stock. Fishing operations can cause ecological impacts of different types: by catches, damage of the habitat, mortalities caused by lost or discarded gear, pollution, generation of marine debris, etc. Periodic reassessment of the tuna potential is also required with adequate inputs from exploratory surveys as well as commercial landings and this may prevent any unsustainable trends in the development of the tuna fishing industry in the Indian Ocean

The Three Mouse Actin-depolymerizing Factor/Cofilins Evolved to Fulfill Cell-Type–specific Requirements for Actin Dynamics

Actin-depolymerizing factor (ADF)/cofilins are essential regulators of actin filament turnover. Several ADF/cofilin isoforms are found in multicellular organisms, but their biological differences have remained unclear. Herein, we show that three ADF/cofilins exist in mouse and most likely in all other mammalian species. Northern blot and in situ hybridization analyses demonstrate that cofilin-1 is expressed in most cell types of embryos and adult mice. Cofilin-2 is expressed in muscle cells and ADF is restricted to epithelia and endothelia. Although the three mouse ADF/cofilins do not show actin isoform specificity, they all depolymerize platelet actin filaments more efficiently than muscle actin. Furthermore, these ADF/cofilins are biochemically different. The epithelial-specific ADF is the most efficient in turning over actin filaments and promotes a stronger pH-dependent actin filament disassembly than the two other isoforms. The muscle-specific cofilin-2 has a weaker actin filament depolymerization activity and displays a 5–10-fold higher affinity for ATP-actin monomers than cofilin-1 and ADF. In steady-state assays, cofilin-2 also promotes filament assembly rather than disassembly. Taken together, these data suggest that the three biochemically distinct mammalian ADF/cofilin isoforms evolved to fulfill specific requirements for actin filament dynamics in different cell types

Deformation mechanisms responsible for the high ductility in a Mg AZ31 alloy analyzed by electron backscattered diffraction

The microstructural evolution during tensile deformation of an AZ31 alloy with grain size ranging from 17 to 40 µm, at intermediate temperatures, has been studied using electron backscattered diffraction (EBSD) and optical microscopy (OM) as the main characterization tools. Two deformation regimes could be distinguished. In the high-strain-rate regime, the stress exponent was found to be about 6, and the activation energy is close to that for Mg self-diffusion. These values are indicative of climb-controlled creep. In the lower strain rate range, elongations higher than 300 pct were measured. In this range, significant dynamic grain growth takes place during the test, and thus, the predominant deformation mechanisms have been investigated by means of strain-rate-change tests. It was found that the stress exponent varied during the test between 1.7 and 2.5, while the activation energy remains close to that for grain-boundary diffusion. The EBSD analysis revealed, additionally, the appearance of low to moderately misoriented boundaries that tend to lay perpendicular to the tensile axis. The enhanced ductility of this AZ31 alloy in this regime is attributed to the operation of a sequence of deformation mechanisms. Initially, grain-boundary sliding governs deformation; once dynamic grain growth occurs, dislocation slip becomes gradually more important. Dislocation interaction gives rise to the appearance of new interfaces by continuous dynamic recrystallization (CDRX).Peer reviewe