Earliest susceptible age of rainbow trout to whirling disease
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AN INVESTIGATION OF THE LARVAL STAGES OF THE SEA LAMPREY ( Petromyzon marinus ), which started in 1960, required a trap that could capture lamprey larvae moving downstream, and that would operate efficiently throughout the year. Sub zero temperatures in the winter and flooding during the spring were the most critical operational problems. Part of the trap was based on the principles of an inclined-plane trap described by Wolf (1951), but the design also incorporated features to prevent ice formation during the winter and to and to strain high flows during the spring runoff.
Study of a virus disease in the chinook salmon (Oncorhynchus tshawytscha ) necessitated the use of a marine environment to study the long range effects of the disease and to complete the life cycle of its etiologic agent. A closed recirculated sea-water system was designed for use under experimental laboratory conditions so that controlled studies of the disease could be made. As others may wish to do marine environment studies in the laboratory, the design and operation of our system are presented. Other systems currently in use have been described by Chin (1959), DeWitt and Salo (1960), McCrimmon and Berst (1966), and the authors of collected papers edited by Clark and Clark (1964). Preparatory to the design and construction of the system in use in this laboratory, visits were made to marine systems in use at the University of Washington's College of Fisheries, Seattle, -washington, and Friday Harbor Laboratory, San Juan Island, Washington; the Washington State Department of Fisheries' Point whitney Shellfish Laboratory, Brinnon, Washington; Humboldt State College, Arcata, California; and the Steinhart Aquarium of the California Academy of Science, San Francisco, California.
No abstract available.
No abstract available.
Trout blood is frequently collected for hematocrit measurements by excising the caudal fin (Snieszko, 1960), but this technique is impractical if valuable fish are to be sampled or if repeated observations are desired. Schiffman (1959) and Snieszko (1960) collected blood from the dorsal aorta and the heart, but these methods are relatively slow and require the preparation of needles and syringes. The use of pointed capillary tubes for cardiac punctures increases the speed of sampling, but body fluids may dilute the blood (Perkins, 1957; Larsen and Snieszko, 1961; and Normandau, 1962). There is need for methods of sampling which are rapid and which neither influence hematological determinations nor harm the fish.
No abstract available.
The artificial propagation of salmon starts with the capture of adults as they ascend rivers to spawn. After capture, they are retained in specially constructed holding areas until sexually mature. Though holding periods vary with species, the spring chinook ( Oncorhynchus tshawytsca ) may be held as long as 4 months before they are spawned. During this interval the fish are often closely confined at unfavorable water temperatures and fatal diseases sometimes reach epizootic proportions. It is important that methods be devised to control or prevent infectious diseases in adult salmon while they are in the holding ponds. Mass treatment is the most convenient way to combat fish diseases. For example, drugs can be administered per os in diets, or chemicals can be added to the water. These methods are mostly ineffective in treating systemic infections of adult salmon because mature salmon do not feed, and many fish diseases cannot be controlled by chemical baths. Thus, effective treatment would require administering drugs to each individual.
A STUDY OF MIGRATORY BEHAVIOR of parasitic sea lampreys ( Petromyzon marinus ) in the Great Lakes required a means of capturing lampreys for tagging and releasing in St. Marys River, Lake Huron. Smith and Elliott (1953) fished specially made gill and trap nets for sea lampreys, but stationary nets could not be used in the St. Marys River because of boat traffic, interference with sport fishermen, and fast currents.
Gill nets are effective for collecting samples of many fish species. These nets may be highly selective in their catch, depending on the mesh size or sizes used and on the size distribution and body shape of the fish in the population. Early studies related mesh selectivity to length or, in a few instances, to length and weight. Later studies showed that the selectivity of gill nets was related more closely to the girth of the fish than to the length, weight, or a combination of these. The girthometer presented here was designed for rapid and accurate measurement of the fish girth. Both speed and accuracy are important when very large numbers of fish are sampled for mesh-selectivity studies. It is also important that a girthometer be sturdy and rigid enough to provide accurate measurements in spite of rough handling and difficult working conditions.
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Sulfamethazine, introduced to fishery medicine by Snieszko and Friddle in 1950, has been widely accepted for treatment of systemic bacterial infections of fish. When administered to fish in their diet, this drug is effective against susceptible bacteria but has the disadvantages of being slowly absorbed (Snieszko and Friddle, 1951) and relatively toxic (Wood, Yasutake, and Johnson, 1957). Today there are many sulfonamides which are more efficacious than sulfamethazine. In domestic animals, sulfisoxazole and sulfadimethoine are absorbed quickly from the gastrointestinal tract and have fewer toxic side reactions, a wider antibacterial spectrum, and better bacteriostatic activity. In the work described in this paper, the efficacies of sulfisoxazole and sulfadimethoxine were compared to the efficacy of sulfamethazine. Experiments were designed to determine the rate of intestinal absorption, the rate of elimination from the blood, the effect on growth, and the toxicity of each drug in juvenile chinook salmon ( Oncorhynchus tshawytscha ). The comparative bacteriostatic activity against two common fish pathogens was also determined for each drug.
Three thousand eyed coho salmon (Oncorhynchus kisutch) eggs from Lake Michigan stock were sent by the Department of Natural Resources to the Fish Control Laboratory, La Crosse, Wis., on January 15, 1969, for use in evaluating candidate fish-cnotrol chemicals.
Abstract not available.
No abstract available.