Geology topics
Publications and source records attributed to R.R. Rucker.
Experiments conducted simultaneously at two laboratories have shown brook trout ( Salvelinus fontinalis ) egg transmission of the virus of infectious pancreatic necrosis with eggs treated with 100 ppm iodine (as Wescodyne ® ) and with nontreated eggs.
An annul mortality among Rainbow Trout (Salmo gairdneri) has plagued the Shelton Hatchery of the Washington State Department of Game for the last several years. No infectious agent could be isolated from the moribund fish, but histopathologica1 changes in the liver of 1-month-old fish suggested the presence of a toxic substance. Scoliosis in 3-month-old fish suggested a possible deficiency in vitamin C. With this background in mind, we designed studies to determine the nature and source of possible toxicants and the role of vitamin C deficiency in the etiology of this disease.
No abstract available.
A description was given of a gram-negative, peritrichously flagellated, fermentative bacterium that was isolated on numerous occasions from kidney tissues of rainbow trout ( Salmo gairdneri ) afflicted with redmouth disease. Although the bacteria apparently were members of the family Enterobacteriaceae, it was impossible to determine their taxonomic position within the family with certainty. Hence it was recommended that their taxonomic position remain sub judice for the present. As a temporary designation RM bacterium was used. Redmouth disease was transmitted from infected to normal fish through the medium of water.
No abstract available.
FORMALIN is used extensively in hatcheries to control external parasites of fish. There are reports that formalin is toxic at some hatcheries, especially when used on rainbow trout ( Salmo gairdneri ). This is a discussion of the development of the use of formalin to control fish parasite-in the hatchery, its properties, and some experimental work.
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.
MERTHIOLATE has been used as a disinfecting agent for green and eyed eggs of various species (Gee and Sarles 1942, Snieszko and Friddle 1948). The present report is a description of the effects of the chemical on green eggs of the chinook salmon ( Oncorhynchus tshawytscha ). The need for this study was indicated when a program of transporting green chinook eggs from various sources to the Coleman National Fish Hatchery at Anderson, California, was required as part of a disease study. There was no available information to indicate whether the salmon eggs would withstand the disinfecting routine shown by Snieszko and Friddle (1948) to be tolerated by trout eggs, or whether the fry and fingerlings from salmon eggs so treated would suffer high mortalities or be abnormal in appearance or activity.
Fish pathology and its role in fish culture were brought into prominence in the spring of 1960 by the disclosure of a high incidence of hepatomas in hatchery-reared rainbow trout. The current problem came to light as the result of a routine inspection of live trout shipments at a California border fish-disease checking station. This service is performed by personnel of the California Department of Fish and Game to preclude the introduction or further spread of communicable fish diseases into California watersheds. Collaborative studies which followed revealed the nationwide distribution of the disease. This unusual disease soon attracted the attention of the Bureau of Sport Fisheries and Wildlife, the Food and Drug Administration, Public Health Service, and several western State health and conservation agencies.
FISH-CULTURISTs, in general, do not agree as to the time of actual fertilization of artificially spawned salmonid eggs. Some fish-culturists believe that the eggs are fertilized in the milt before water is added, while others are equally certain that fertilization is not achieved until after water is added. This difference of opinion has probably existed since the advent of the dry spawning method, in which milt is added to the eggs without the presence of water in the spawning pan. According to the "Manual of Fish-Culture" published by the U. S. Commission of Fish and Fisheries in 1900, it was known that eggs and milt from salmon maintain their viability for many hours if held in open containers, that both eggs and milt soon lose their viability when water is added, and that the milt and fluid around the eggs can be "utilized in impregnating masses of eggs when there is a scarcity of males, as sometimes occurs toward the close of the spawning season." The object of the studies reported here was to confirm some of the foregoing observations and to determine whether salmonid eggs could be fertilized without the supportive action of water.
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.
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.
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.
Since 1951 a disease, usually occurring in late spring or early summer, has caused severe losses in 3- to 12-month-old fingerling sockeye salmon in hatcheries in the State of Washington. The disease is characterized by an explosive outbreak, mortality usually 80 percent or greater, and a residual spinal deformity in a small percentage of the surviving fish, and its specificity for the one species of salmon, Oncorhynchus nerka. (The anadromous strain of this species is commonly known as sockeye, blueback, or red salmon, while the fresh-water strain is called kokanee or silver trout.) The etiological agent is believed to be a virus.
Production records for 1885, 1891–1908, and 1929–49, indicate cyclic fluctuations for several important species of fish. The average annual take (all species) of 3,582,000 pounds in 1929–49 was 3,503,000 pounds below the 1891–1908 mean of 7,085,000 pounds. Decline in the output of lake herring alone from 5,841,000 pounds in 1891–1908 to 1,070,000 pounds in 1929–49—a drop of 4,771,000 pounds—more than accounted for the decrease. For species other than lake herring the combined output increased from 1,244,000 pounds in 1891–1908 to 2,512,000 in 1929–49—a rise of 1,268,000 pounds. The 1929–49 fluctuations of abundance (as estimated from records of catch per unit of effort) were considerable for all principal species. In the late years of the period, lake trout were scarce as the result of sealamprey depredations, but the abundance levels of whitefish, lake herring, and walleyes were extremely high; at the same time the smelt was showing good recovery from the disastrous 1943 mortality. With certain exceptions, correlations between fluctuations of fishing intensity and the abundance of individual species were low, probably because most operations are based on several species and hence not ordinarily sensitive to changes in the abundance of a particular one. A combination of intensive fishing and high abundance of three principal species carried the production to 5% million pounds in 1947 and the modern record high of between 7% and 8 million pounds in 1948 and 1949. With this prosperity has developed a most difficult situation arising from friction between local commercial fishermen and newcomers from other areas and from the activities of sport fishermen and resort owners who believe that drastic restrictions on commercial fishing will insure a perpetual high level of abundance of walleyes. Statistics for 1950 are given in a supplement.
GILL DISEASE among fish, a disease which is characterized by a proliferation of the gill epithelium, has been attributed to a number of different causes. Generally, there are two recognized types: the eastern or bacterial type, in which long filamentous bacteria can always be demonstrated; and the western type, in which, by definition, bacteria cannot be demonstrated.