Recent Arctic warming vertical structure contested.

The vertical structure of the recent Arctic warming contains information about the processes governing Arctic climate trends. Graversen et al. argue, on the basis of ERA-40 reanalysis data, that a distinct maximum in 1979-2001 warm-season (April-October) Arctic temperature trends appears around 3 km above ground. Here we show that this is due to the heterogeneous nature of the data source, which incorporates information from satellites and radiosondes. Radiosonde data alone suggest the warming was strongest near ground.

Pasteurella skyensis sp. nov., isolated from Atlantic salmon (Salmo salar L.).

From four separate incidents of disease in farmed Atlantic salmon over a four-year period, gram-negative rod-shaped bacteria were consistently isolated by culture on sea-water blood agar. Biochemical and physiological tests indicated that the organism was related to the family Pasteurellaceae, and this was confirmed from the 16S rRNA gene sequence. Comparison of the 16S rRNA gene sequence with those of 45 members of the Pasteurellaceae showed that the closest phylogenetic relationship was with an organism termed 'Pasteurella phocoenarum', isolated from a porpoise, for which the 16S rRNA gene sequence has been recorded but for which the properties have yet to be published. It is proposed that this bacterium isolated from salmon should be classified as a new species, namely Pasteurella skyensis sp. nov. The type strain of Pasteurella skyensis sp. nov. is strain 95A1T (= NCTC 13204T = NCIMB 13593T).

Sea lice infestations on farmed Atlantic salmon in Scotland and the use of ectoparasitic treatments.

A recently compiled national database on sea lice infestations on farmed Atlantic salmon, contains detailed records for the period 1996 to 2000 from over 30 commercial sites on the west coast of Scotland. The data indicate that the two prevalent species of lice, Lepeophtheirus salmonis and Caligus elongatus, have different trends in abundance and distinctive seasonal patterns of infestation on farmed salmon. For the economically important species L salmonis, its abundance on fish varies with the time of the production cycle, the time of year and the particular year. Weekly fluctuations in sea lice counts indicate that treatment can be very effective in controlling infestations but that the counts recover rapidly and regular treatments are necessary to ensure control. A comparison of sites using medium or large numbers of treatments suggests that they do not reduce sea lice infestations to the same levels. There is also evidence that sites using treatments based on different chemical constituents had significantly different levels of infestation.

Plasma lipase concentration as an aid to the early detection of pancreas disease in farmed Atlantic salmon (Salmo salar).

Plasma lipase concentrations were determined in Atlantic salmon post smolts at weekly intervals on two farms from late June. On one farm there was a significant increase (P < 0.001) in lipase concentration which coincided with a suspicion of pancreas disease on clinical grounds. A definitive diagnosis was subsequently confirmed by histopathology. The exercise was repeated on 10 farms in the following year and the results provided additional evidence of the value of monitoring lipase concentration as an indication of pacreas disease at an earlier stage than it can be detected by clinical signs and histopathology alone.

Assessment of the antimicrobial sensitivity of Aeromonas salmonicida isolates from farmed Atlantic salmon in Scotland.

Sixty-five isolates of Aeromonas salmonicida were assessed for antimicrobial sensitivity by disc diffusion tests and the results compared with the minimum inhibitory concentration for each isolate. The results demonstrated that disc diffusion, using a standard technique, may be used to categorize isolates as sensitive or resistant provided that the corresponding minimum inhibitory concentrations are known.