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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Wildlife and Fisheries Science

First Advisor

David W. Willis


Fish catch rates in passive gear, such as gill nets, are commonly used by biologists to index fish population density. The purpose of this project was to assess the potential relationship between common carp (Cyprinus carpio) biomass and catch-per-unit-effort (CPUE) in gill nets. Adult common carp population/biomass estimates were made and compared to CPUE data obtained during the summers of 1988 and 1989, at Arrowwood (North Dakota) and Sand Lake (South Dakota) National Wildlife Refuges. Population/biomass estimates were undertaken at three different areas within each refuge. A consistent pattern was evident throughout the population/biomass estimates, with the larger, more open areas having the highest biomass, and the smaller, more shallow coves having the lowest. Biomass estimates ranged from 0.0 to 2,409.4 kg/hectare. Gill net index netting was also conducted during the summers of 1988 and 1989. Sampling was done during the third weeks of May, June, July, and August. The mean catch rates of common carp increased from May to June, and decreased thereafter. In general, variability as a percentage of the mean increased throughout the summer, and was typically lowest during May. Two techniques were used to assess the relationship between common carp biomass and CPUE data. First, only Sand Lake National Wildlife Refuge data were used (two data pairs), and second, Sand Lake and Arrowwood National Wildlife Refuge data were combined in a single analysis (three data pairs). By either technique, a positive relationship was found between common carp biomass and CPUE data. However, neither comparison provided a statistically supported relationship. To obtain a statistically valid, linear regression model, more data pairs must be added. The best sampling design for indexing common carp in Arrowwood and Sand Lake National Wildlife Refuges would involve increased effort during May using experimental gill nets. May typically had the lowest variability as a percentage of the mean catch rate, meaning that reliable catch rates could be obtained with the least effort. A switch from the three-net complement used in this study to an experimental gill net would allow each net to capture the entire length range of adult common carp. Based on data from May, 1989, 43 units of effort would be needed to estimate, within 20%, the mean catch rate at the 95% confidence level. Using the current three-net complement, 129 nets would have to be set to obtain the desired level of precision. With experimental nets, only 43 nets would likely need to be set.

Library of Congress Subject Headings

Carp--South Dakota--Counting
Carp--North Dakota--Counting
Gillnetting--South Dakota--Catch effort
Gillnetting--North Dakota--Catch effort


Includes bibliographical references (pages 44-46)



Number of Pages



South Dakota State University


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