Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Natural Resources

Department name when degree awarded



William F. Sigler


The study of the Utah sculpin in Logan River was based on 801 specimens collected during 1949 to March 1951. Numbers of fish examined for various catagories of the study wares length-frequency, 495; aging by vertebrae, 407; length-weight relationship, 601; and food habits, 275.

Fish were collected by use of an electric shocking machine generating 600 watts and 220 volts. Numbers of fish occurred as high as 150 per tenth mile of stream. Preferred habitats occurred in areas of coarse gravel and small rocks.

Vertebrae dissected from the fish were used in age determination. Length-frequency proved to be a general correlation to the aging technique. Fish were difficult to sex by external observation except during the breeding season.

Relationship between standard length and weight is described by the following formula:

W = 4.236 X 10-4 L2900

The coefficient of condition (K) increased with length up to 60 millimeters in standard length and decreased in length in fish ranging from 60 to 125 millimeters in standard length. The greatest variation in K occurred in fish below 50 millimeters in length. The factor for converting total length to standard length as determined from 601 specimens between 24 and 112 millimeters. standard length was 0.812. The factor for converting standard length to total length for the same fish was 1.232.

The bulk of the diet consisted almost entirely of aquatic insects. Most of the aquatic insects were diptera. Ephemeroptera, plecoptera, and trichoptera were consumed in almost equal numbers. Food availability and preference were determined from bottom samples of the river. Competition for food is minimized somewhat by the fact that the sculpin is a bottom feeder and the trout is primarily a surface feeder. Predation of trout eggs by the sculpin was almost non-existent.