Geology topics
Publications and source records attributed to A. J. Ross.
Epizootics among chinook salmon fingerlings at the Coleman National Fish Hatchery have occurred periodically since 1941. A virus or virus-like filterable agent has been demonstrated to be the causative agent of this disease.
Incidence of acid-fast bacillus infections in salmonid fishes at West Coast hatcheries was determined for 1957-59. No evidence was obtained which would indicate a definite trend towards either increased or decreased rates of infection. It is apparent that the incidence of infection is higher in hatchery-marked fish than in unmarked fish. Only one hatchery was found free of infection during the 3 years covered by the investigation. This installation had never used raw salmon products in diet.
No abstract available.
THE INCLUSION OF VISCERA AND CARCASSES OF TUBERCULOUS ADULT SALMON IN THE DIET OF JUVENILE SALMONIDS is considered to be the major source of mycobacterial infections in hatchery-reared fish (Wood and Ordal, 1958; Ross, Earp, and Wood, 1959). In considering additional modes of infection, we speculated about transovarian transmission or a mechanical process arising from contamination of the ova at the egg-taking stage with subsequent entry of the bacteria into the egg at the time of fertilization. This paper is a report on observations made during an experiment designed to test the latter theories.
Consideration is given to a recurring disease of early feeding chinook salmon fingerlings at the Coleman, California, Federal Fish Cultural Station. The infection becomes manifest in the early spring months at low water temperatures and abates as the water temperature rises. Bacteriological studies have failed to yield the presence of a disease agent, either by cultural or staining procedures. The disease has been successfully transmitted from infected fish to healthy fish by the injection of bacteria-free filtrates prepared from diseased fish tissue. The causative agent is therefore believed to be a virus-like entity.
On May 26, 1959, two of the authors' investigated a fish kill at Dailey Lake, Park County, Montana. They observed about a half-dozen live, weakly swimming yellow perch ( Perca flavescens ), in addition to thousand of dead perch along the shoreline. It was learned from local residents that mortalities had begun to appear some 2 weeks earlier. At that time the time the authorities had diagnosed the condition as a winterkill, since ice had only recently disappeared from the lake. Although a number of other species inhabit Dailey Lake, including rainbow trout (S almo gairdner i), brown trout ( S. trutta ), kokanee ( Oncorhynchus nerka ), black crappie ( Pomoxis nigromaculatus ), largemouth bass ( Micropterus salmoides ), longnose suckers ( Catostomus catostomus ), rainbow x cutthroat hybrids, only one other species was represented in the kill. This consisted of one black crappie. Examination of the freshly dead perch revealed the presence of multiple petechiae, which were visible externally as well as in the dorsal musculature. The peritoneal cavity showed evidence of inflammation and contained a bloody ascitic fluid. A number of the dead fish were placed on ice and shipped to the Western Fish Disease Laboratory in Seattle for bacteriological studies.
The presence of mycobacteria in salmonoid fishes was first recorded by Earp, Ellis, and Ordal (1) in 1953. Acid-fast bacilli had previously been reported from other cold-blooded animals including fishes of fresh-water and marine origin; recent reviews have been presented by Vogel (2) and Parisot (3). The initiation of an intensive search for bacteria of this group revealed their widespread distribution in salmonoid fish populations. Acidfast bacilli have been demonstrated in livers and kidneys of salmon and trout in Washington, Oregon, and California, as well as from salmon taken in Alaskan waters. While the organisms are generally considered to be associated with fish of hatchery origin (4), they have also been found in young and adult fish from areas presumably supporting only wild populations. Wood and Ordal (4) indicate that the incidence of the tuberculosis-like infection is directly related to the length of time the fish are reared in the hatchery prior to release. This may result from a common hatchery practice of feeding viscera and carcasses from spawned-out adults to juvenile fish. Therefore, in many instances viable mycobacteria are present in the food of young fish.
Epizootics among chinook salmon fingerlings at the Coleman National Fish Hatchery have occurred periodically since 1941. A virus or virus-like filterable agent has been demonstrated to be the causative agent of this disease.
No abstract available.
Violent epizootics among hatchery reared sockeye salmon fingerlings ( Oncorhynchus nerka ) caused by a filterable agent have occurred. In 1954, one source of this infectious, filterable agent was found to be adult sockeye viscera used in the diet for the fingerlings. The results of observations on an epizootic in 1958 indicate that the infection may be transmitted to fingerlings from a water supply to which adult sockeye salmon have access.