Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)




The importance of fish parasites is directly related to the value of the fish they affect. Alaskan salmonids are extremely important and are constantly increasing in value to the United States. Other countries, such as Japan and Russia, are also finding Alaskan salmonids important as a foodstuff. If human populations continue growing at present rates, in only a few years there could be twice as many people eating fish. As a recreational asset in Alaska, salmonids rank at or near the top, both for sportfishing and as a natural attraction. It is thus important from an economic point of view that we have a knowledge of the parasites of our freshwater and marine fishes. Parasites are always present in natural populations of animals. Normally, the parasites are in a complex dynamic equilibrium with their hosts. Fish are exposed to a considerable range of parasites, which may occur in large numbers. If some unusual event occurs in the environment, the equilibrium between parasite and host may be upset and an epizootic of parasites may occur. Regulating mechanisms in the environment eventually will restore this balance, but before a new equilibrium is established there may be a serious fish loss. Once sound background knowledge is attained, it may be possible to avoid undesirable interference in natural waters. To control the more harmful parasites, an understanding of the biology of the parasites is required. Hoffman stated that before treatment or control of fish parasitic diseases can be best achieved, the study of fish parasites should follow a logical pattern: 1. Identifying the parasite. 2. Obtaining a thorough knowledge of its life history, which may be simple or very complicated. 3. Learning the ecological requirements of the parasite, such as host specificity, optimum temperature, pH, nutrition, and other metabolic requirements. 4. Mapping the geographic range of the parasite. 5. Determining the effect of immunologic mechanisms of the host on the parasite or vice versa. 6. Studying control and treatment methods. The primary objectives of my research were: 1. To determine the incidence and identity of parasites found in salmonid fishes in southcentral Alaska. 2. To assist in mapping the geographic range of the parasites.

Library of Congress Subject Headings

Salmon -- Diseases Fishes -- Alaska Fishes -- Parasites



Number of Pages



South Dakota State University