Microstructure and high-temperature mechanical properties of Inconel 718 superalloy weldment affected by fast-frequency pulsed TIG welding

An economically-important Antarctic toothfish (Dissostichus mawsoni) longline fishery operates in the Ross Sea region (RSR), in the Southern Ocean. Management of this fishery according to Article II of the Convention on the Conservation of Antarctic Marine Living Resources aims to minimise the risk of depletion of the species that are caught as bycatch. We employed spatio-temporal models fitted to catch rate data reported by fishing vessels between 2003 and 2020 to understand the spatio-temporal abundance patterns of the major species groups caught as bycatch in the RSR Antarctic toothfish fishery. The study region consisted of the areas of the RSR where fishing has occurred since the inception of the longline fishery. The study species groups included macrourids (Macrouridae), skates (Rajiformes), icefish (Channichthyidae), eel cods (Muraenolepididae) and morid cods (Moridae). The Akaike information criterion-selected models included the effect of bottom depth and, often, also the effect of surface chlorophyll-a concentration. We found that bottom depth explained only a very small proportion of the variance in the data, while surface chlorophyll-a concentration explained very little of the variance. The predicted long-term trends of three species groups were clear: the relative abundance of macrourids has decreased, while those of skates and icefish have increased. We resampled from the predictive distributions to identify the abundance hotspots of each of the species groups, defined as the areas where long-term log-relative abundance (i.e., mean log-relative abundance over the study period) was at or greater than the average long-term log-relative abundance over the entire study region. From these abundance hotspots for the individual species groups, we developed two alternative composite hotspot indices. Both composite hotspot indices were highest on the Ross Sea continental shelf slope, between 160 degrees E and 175 degrees W. Our results can be used to guide the setting of bycatch limits and inform fishing vessels about bycatch species abundance hotspots in the RSR. We also recommend that future modelling studies seek to disentangle the direct and indirect impacts of the RSR Antarctic toothfish fishery on the bycatch species which are also prey of Antarctic toothfish.