A telephone survey of eel fishermen regarding external lesions and mortalities of American eels (Anguilla rostrata) from Lake Ontario and the St. Lawrence River basin, Canada.
Signs of decreasing landings and recruitment have been observed during the last decade in American eels (Anguilla rostrata) from the St. Lawrence River basin, Canada. A study was undertaken to examine whether important manifestational diseases among commercial catches could be associated with these declines. During this survey, 56 fishermen from Lakes Ontario, Saint-François and Saint-Pierre, the Richelieu River, the Québec City area and the St. Lawrence Estuary were interviewed. Most fishermen from every area reported decreasing catches since the 1980s. Eel mortalities were reported from 1990 to 1992 in Lake Saint-François, Lake Saint-Pierre and the Québec City area, but in apparently lower magnitude than in the past decades. The lesions observed on dead eels in Lake Saint-François indicated that the cause of the mortalities might be associated with the upstream hydroelectric dam. Eels with 'scratches all over the body' were only observed in the St. Lawrence Estuary. Fishermen from almost every area reported that they had observed eels with 'crooked tail', 'humpback' and 'cut tail' in low frequency in 1992. The questionnaire data were validated by comparing some of the results of the questionnaire survey and a processing plant survey in 1992. The use of questionnaires for assessing fish diseases in commercial species is discussed. The results of this survey do not indicate that the health of the American eels from the St. Lawrence River basin is severely impaired. However, the magnitude of diseases and mortalities was probably underestimated.
Changes in Maturity, Plasma Sex Steroid Levels, Hepatic Mixed-Function Oxygenase Activity, and the Presence of External Lesions in Lake Whitefish (Coregonus clupeaformis) Exposed to Bleached Kraft Mill Effluent
Lake whitefish (Coregonus clupeaformis) exposed to primary treated bleached kraft mill effluent (BKME) had reduced gonadal development and increased liver size relative to two reference populations. These results parallel our previous work on the white sucker (Catostomus commersoni) exposed to BKME at the same Lake Superior site. More detailed studies conducted in 1990, after the installation of an aeration stabilization basin at the pulp mill, found that lake whitefish exhibited reduced gonad sizes, delayed age to maturation, decreased levels of the plasma sex steroids testosterone and 17β-estradiol, and elevated hepatic mixed-function oxygenase (MFO) activity. Liver size was smaller following operation of the secondary treatment system. More than 20% of the lake whitefish collected at the BKME site in 1990 exhibited lateral, slash-like lesions which penetrated the body cavity. Histological examination revealed no evidence of an infectious etiology, and the wounds could not be accounted for by known caus...
Shape and surface texture of molten droplets deposited on cold surfaces
When a molten droplet impacts on a cold surface, the interaction between solidification and fluid dynamics can lead to different shapes and surface textures of deposited droplets. This article presents an experimental study on deposition of small droplets (39 μm diameter) of molten wax ink on solid surfaces. Our results show that both the final shape and the surface texture of deposited droplets are extremely sensitive to deposition conditions, which include initial temperature of droplets, type of substrate surface and distance between substrate and printhead. Different surface textures are observed and shown to depend on the thermal and flow histories of ink droplets during the process of impact. A test using crystalline wax reveals crystallization as one of the major factors in determining the final texture.