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Cores acquired from the Ross Sea continental shelf and continental slope during the XXX Italian Programma Nazionale di Ricerche in Antartide (PNRA) were analysed and yielded interesting micropalaeontological, biostratigraphic diatom results and palaeoceanographic implications. These multi-proxy analyses enabled us to reconstruct the glacial/deglacial history of this sector of the Ross embayment over the last 40 000 years, advancing our understanding of the Last Glacial Maximum (LGM) environmental and sedimentological processes linked to the Ross Sea ice sheet/ice shelf fluctuations in a basin and continental-slope environment, and allowed us to measure some of the palaeoceanographic dynamics. The central sector of the Ross Sea and part of its coast (south of the Drygalski Ice Tongue) enjoyed open marine conditions in the pre-LGM era (27 500–24 000 years bp). The retreat of the ice sheet could have been influenced by a southward shift of a branch of the Ross gyre, which triggered early deglaciation at c. 18 600 cal bp with a significant Modified Circumpolar Deep Water inflow over the continental slope at c. 14 380 cal BP. We assume that a lack of depositional material in each core, although at different times, represents a hiatus. Other than problems in core collection, this could be due to the onset of modern oceanographic conditions, with strong gravity currents and strong High Salinity Shelf Water exportation. Moreover, we presume that improvements in biostratigraphy, study of reworked diatom taxa, and lithological and geochemical analyses will provide important constraints for the reconstruction of the LGM grounding line, ice-flow lines and ice-flow paths and an interesting tool for reconstructing palaeo-sub-bottom currents in this sector of the Ross embayment.

Accurate estimates of escapement by adult anadromous salmonids are difficult, especially in large, multistock river systems. We used radiotelemetry and a fishery reward program to calculate escapement, harvest, and unaccounted for loss rates for 10 498 adult chinook salmon (Oncorhynchus tshawytscha) and 5324 steelhead (Oncorhynchus mykiss) during six return years in the Columbia River basin. Mean annual escapements to spawning sites, hatcheries, or the upper bounds of the monitored hydrosystem were 73.4% (spring-summer chinook salmon), 61.3% (fall chinook salmon), and 62.6% (steelhead). Mean reported harvest rates were 8.7% (spring-summer chinook), 22.0% (fall chinook), and 15.1% (steelhead) within the mainstem hydrosystem and 5.9%, 3.4%, and 5.7%, respectively, in lower hydrosystem tributaries. On average, 12%-17% of each run had unknown fates in the mainstem hydrosystem. Escapement, harvest, and loss varied significantly between runs and years, within runs between known-origin subbasin stocks, and between interdam river reaches. Multiyear quantitative assessments like this can reduce uncertainty, clarify inter- and intra-annual variability, and help managers better evaluate fisheries, identify conservation priorities, and help protect evolutionarily significant populations. Resume : Il est difficile d'estimer avec precision les echappements des salmonides adultes, particulierement dans les grands reseaux hydrographiques qui contiennent plusieurs stocks. Nous avons utilise la radiotelemetrie et un pro- gramme de peche avec recompenses pour calculer l'echappement, les captures et les taux de pertes inexpliquees pour 10 498 saumons quinnat adultes (Oncorhynchus tshawytscha) et 5324 truites arc-en-ciel anadromes (Oncorhynchus my- kiss) durant six annees de montaison dans le bassin hydrographique du fleuve Columbia. Les echappements annuels moyens vers les sites de fraie, les piscicultures et les limites superieures du systeme hydrographique sous surveillance sont de 73,4 % (saumons quinnat de printemps et d'ete), 61,3 % (saumons quinnat d'automne) et 62,6 % (truites arc- en-ciel anadromes). Les taux moyens de captures signalees sont de 8,7 % (saumons quinnat de printemps et d'ete), 22,0 % (saumons quinnat d'automne) et 15,1 % (truites arc-en-ciel anadromes) dans le cours principal et respective- ment de 5,9, 3,4 et 5,7 % dans les tributaires du cours inferieur. En moyenne, le sort de 12-17 % des poissons de chaque montaison reste inconnu dans le cours principal. L'echappement, la capture et la perte varient significativement d'une montaison a une autre et d'une annee a l'autre; ils varient aussi au sein d'une meme montaison parmi les stocks identifies comme provenant de divers sous-bassins, de meme que dans les divers troncons de riviere entre les barrages. Des estimations comme les notres qui couvrent plusieurs annees peuvent reduire l'incertitude, preciser la variation an- nuelle et inter-annuelle et aider les gestionnaires a mieux evaluer les peches, fixer les objectifs prioritaires de conserva- tion et proteger les populations d'importance evolutive.

An understanding of the migration timing patterns of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss is important for managing complex mixed-stock fisheries and preserving genetic and life history diversity. We examined adult return timing for 3,317 radio-tagged fish from 38 stocks of Columbia River basin spring–summer Chinook salmon O. tshawytscha over 5 years. Stock composition varied widely within and between years depending on the strength of influential populations. Most individual stocks migrated at similar times each year relative to overall runs, supporting the hypotheses that run timing is predictable, is at least partially due to genetic adaptation, and can be used to differentiate between some conspecific populations. Arrival timing of both aggregated radio-tagged stocks and annual runs was strongly correlated with river discharge; stocks arrived earlier at Bonneville Dam and at upstream dams in years with low discharge. Migration timing analyses identified many between-stock ...