BEHAVIOR AND SEGREGATION OF THE DALL ' S PORPOISE IN THE NORTHWESTERN NORTH PACIFIC OCEAN
To improve knowledge of the life history of Dall's porpoise, Phocoenoides dalli (True, 1885) that are incidentally caught by the Japanese salmon mothership fishery in the northwestern North Pacific, a 34-day cruise was conducted during August-September, 1982, after the fishing season. A total of 710 Dall's porpoise were sighted and 80 were caught using hand-held harpoons. The species' southern limit was at 41°N latitude, at a surface water temperature of l8°-l9°C, and overlapped the range of Lissodelphis and Lagenorhynchus. Distribution of the truei-type was limited to the Japanese coastal waters and the number sighted was negligible east of 155°E. Density of Dall's porpoise was higher in the western and northern parts of the research area, and somewhat lower in the southeast. More Dall's porpoise rode the ship's bow wave during mid-day than in the morning or evening, and in areas where the surface water temperature was 11°C or above. In areas with a surface water temperature of 11°C or below, most of the Dall's porpoise avoided the ship. The latter areas had a high number of mother-calf pairs and calves possibly weaned, none of which rode the bow wave. Adults not accompanying calves were sighted in both areas. School size was not different between the two areas. Most of the specimens were taken in the southern part of the study area. Males predominated and most were 2 to 6 years old, around the age of attainment of sexual maturity. Lactating individuals were significantly scarce in the sample. The dalli-type reached sexual maturity at a smaller body length than the truei-type. Based upon comparisons of results from this cruise with those obtained from the salmon mothership fishery since 1978, we conclude that, during the season from June through September, (I) females in the state of late pregnancy, lactation, or pregnancy and simultaneous lactation are mainly distributed in the northern area, and (2) the southern area is mainly occupied by males and some females not accompanied by calves. 1 Present address: Far Seas Fisheries Research Laboratory, 5-7-1 Orido, Shirnizu-shi, Shizuoka-ken 424, Japan. Sci. Rep. Whales Res. Inst., No. 35, 1984, 107-128 108 KASUYA AND JONES
Abundance and Seasonality of Dall’s Porpoise (Phocoenoides dalli) in Southeast Alaska.
Little is known about Dall’s porpoise (Phocoenoides dalli) population biology in Southeast Alaska. Here we present the first abundance estimates for Dall’s porpoise in the waters of Southeast Alaska. We studied the density and abundance of Dall’s porpoise during 19 line-transect vessel surveys covering the major inland waters of Southeast Alaska between the months of April and September, from 1991 to 2012. Dall’s porpoise was the most frequently encountered odontocete (toothed cetacean) within the study area and abundance was estimated with multiplecovariate distance sampling methods. Highest abundance was recorded in spring months (N = 5,381, CV = 25.4%), with lower numbers in summer (N = 2,680, CV = 19.6%), and lowest in fall (N = 1,637, CV = 23.3%). Peak density in spring months (31.6 porpoises/100 km2) was the highest ever reliably recorded for inshore areas of the species’ range. Estimates of abundance for comparable areas (i.e., those surveyed consistently in each study year) showed strong yearly fluctuations, and demonstrate that this species is a common inhabitant of these waters from at least spring to early fall.
Phase characterisation of simulated high burn-up UO2 fuel
Abstract To determine the lattice constant variation with burn-up and the oxidation behaviour at high temperatures, simulated UO2-spent fuels with burn-ups up to 200 GWd tM−1 were prepared by cold pressing and sintering and characterised by X-ray diffraction analysis and thermogravimetry. The fcc-lattice parameter of the sintered samples determined at room temperature, showed a continuous decrease with the simulated burn-up. During oxidation the conversion of the simulated fuels to the (U,FP)4O9 and (U,FP)3O8-type phases was strongly delayed when the simulated burn-up exceeded 80 GWd tM−1. Also, at high burn-ups (>100 GWd tM−1), large fractions of the (U,FP)4O9-type phase remained untransformed to (U,FP)3O8 after prolonged exposure to air at 950–1000°C. This suggests a marked widening of the (U,FP)4O9-phase field when the amount of substituted uranium atoms exceeds values of about 8%.