Mycotic aspects of epizootic ulcerative syndrome (EUS) of Asian fishes

Abstract A survey of fish affected with epizootic ulcerative syndrome taken from outbreaks in countries throughout South and South-East Asia showed that a morphologically typical fungus was consistently present within lesions. Although the majority of the fungal mycelium was dead in most lesions it proved possible to isolate a very delicate and culturally demanding Aphanomyces from such lesions in a few cases. It also proved relatively easy to isolate other members of the Saprolegniaceae including Aphanomyces from the surface of lesions, but these were considered saprophytes derived from background spore burdens in the water. Sporangium morphology of the putatively pathogenic isolates of Aphanomyces was different from that of saprophytic Aphanomyces strains and they also had a lower thermal tolerance. When a mycelium from these strains was placed below the dermis of healthy fish, it caused an inflammatory response and proceeded to migrate down into the tissues of the fish, inducing severe myonecrosis with chronic epithelial reaction. The saprophytic isolates induced a local host response followed by healing of the induced lesion, and destruction or expulsion of the mycelium. It is considered that the specific slow-growing, thermo-labile Aphanomyces is the pathogenic fungus which causes so much tissue damage in this disease, although it may not be a primary pathogen in its own right.     

Diel vertical distribution of postflexion larval Citharichthys spp. and Sebastes spp. off central California

The diel and spatial distributions of postflexion larval Citharichthys spp. and Sebastes spp. at 67 stations off central California were examined during March 1994 with a 10 m² MOCNESS during 24 h sampling operations. At each station, a CTD profiler with an attached PAR sensor was deployed to measure temperature, salinity, σ_t, dynamic height, and ambient light levels at depth. Catches of C. sordidus, C. stigmaeus, unidentified Sebastes spp., and S. jordani were larger at night than during the day and crepuscular periods, probably because of net avoidance during the day and crepuscular periods, and (for Citharichthys spp.) vertical migration into the upper water column at night. C. sordidus and C. stigmaeus migrated vertically through the pycnocline on a diurnal cycle, while Sebastes spp. apparently remained in the mixed layer above the pycnocline at all times. No definitive patterns were observed between horizontal contours of temperature, salinity, and σ_t at depth and catches of any larvae. This was attributed to the relatively homogeneous spatial pattern in the water column above the pycnocline, where the majority of the fish occurred.     

Moderation of the experimental carrageenin granuloma in the plaice, Pleuronectes platessa L., by reduction in temperature

Abstract. A standard carrageenin granuloma was induced in adult plaice, Pleuronectes platessa L., maintained at 5°C and its pathogenesis followed histologically for 3 months. All of the stages of granulation were considerably delayed compared to similar lesions reported at 10°C. The lesion was only partly resolved at the end of the study, and many of the cellular changes were less exuberant and less well-defined than those reported for 10°C.