Progressive panophthalmitis in chinook salmon, Oncorhynchus tshawytscha (Walbaum): a case report

Abstract. This report describes the gross and histopathological appearance as well as the bacteriological findings in an outbreak of panophthalmitis in farmed chinook salmon. In all cases, the bacteria were either Mycobacterium neoaurum or an unidentified Rhodococcus spp.; in some fish, both types were present in roughly equal numbers, while in others, one type dominated. Despite occasionally recovering the bacteria from kidney or spleen, no lesions were found in these or in any other organ, suggesting that the localization to the eye was not incidental, but a specific tropism. Nevertheless, the possibility of predisposing cause(s) must be considered and these are discussed.     

Voting with Their Feet: Jobs versus Amenities

ABSTRACT The determinants of rural and urban community population change over the period 1991–2001 are investigated at a very fine level of disaggregation for Canada. The study examines the influence of local amenities, economic factors, and agglomeration economies on population growth for age cohorts starting from the very young to the elderly. Motivated by the objective of assessing the overall jobs versus people question in economic development, the emphasis is on estimating the relative contribution of groupings of variables in explaining the variations in population change rather than the contribution of individual variables. Results indicate that rural and urban populations are influenced to differing degrees by amenity, economic, and urban scale groupings of variables and that there are variations among age cohorts in both urban and rural areas. While economic variables are the most influential in population change for all rural cohorts, their contribution somewhat diminishes with age. In urban areas, amenity, and economic variable groupings have approximately equal importance across all cohorts. For the key young adult cohort, the economic grouping is clearly the most influential in rural areas, while it is a close second to amenities in urban areas.     

Post-spawning mortalities in brown trout Salmo trutta L.

Abstract. An 'oedema syndrome' caused mortality of 55·5% in brood brown trout approximately 2 months after spawning. The pathology and clinical biochemistry of the condition are described. It is suggested that the severe hypoproteinaemia and anaemia were due mainly to the traditional reduction in feed levels prior to spawning at a time when the water temperatures were abnormally high. It is also suggested, however, that the syndrome would not have occurred if the fish had not developed an aeromonad infection prior to stripping. Concurrent fungal infection and subsequent extremely low water temperatures are also thought to have played a role.     

Comparison of natural populations of Mycosphaerella graminicola from single fields in Kansas and California

Kansas and California wheat-growing regions differ dramatically in soils, climate, wheat cultivars, crop rotation patterns, and cultural practices, which could select for different fungal populations of Mycosphaerella graminicola. Our objective in this study was to use amplified fragment length polymorphism (AFLP) loci to assess the genetic diversity of M. graminicola populations within single fields in two widely separated, and geographically isolated sites in Kansas and California. Three primer-pair combinations were used to resolve polymorphism at 177 loci in 67 and 63 isolates from Kansas and California, respectively. Genotypic variability was high, which is consistent with a genetically diverse initial inoculum. There was no evidence of genetic disequilibrium in either population, with only 4.6% of the locus pairs in Kansas, and 5.4% of the locus pairs in California in detectable disequilibrium. The migration rate calculated between the two sites was as low as 1.8 individuals per generation, and significant differences in allele frequencies were observed. Therefore, these two populations do not represent mere subsamples of a larger, randomly mating population. This is a rare report of isolation by distance occurring between two North American populations of M. graminicola, indicating that at least some of these populations may be differentiating. Although genetic isolation by distance may occur, we cannot exclude movement of new gene combinations such as fungicide resistance or virulence between these two locations.