Date of Award

8-1-1983

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

Various aspects of the ecology and biology of the walleye were examined from three discrete areas of Lake Sakakawea during the summer of 1982. Spatial distribution, predator-prey relationships and species association data were procured by simultaneously placing experimental and 0.5 in mesh gill nets at three depth ranges: 0-10 ft, 11-20 ft and 21-40 ft. Temporal distribution data were collected by lifting and resetting the gill nets approximately every six hours. Four time periods were used: 0600-1200 h, 1200-1800 h, 1800-2400 h and 2400-0600 h. Walleye age, growth and food habit data were also collected from the fish caught.

The Van Hook Area produced the largest numbers of walleye and rainbow smelt, 03merus mordax (Mitchill). The 0-10 ft range produced the largest catches of walleyes for all areas. The total rainbow smelt catch was the largest in the 21-40 ft range. The Williston Area had the largest rainbow smelt catch in the 0-10 ft range. The total catch of walleye and rainbow smelt was significantly correlated for the 12 sampling periods. Walleyes and rainbow smelt numbers were also significantly correlated in the 11-20 ft range. More saugers, otizostedion canadense (Smith), were caught in the Wiiliston Area than walleyes. The differences in the total walleye and rainbow smelt catch among time periods were s/nall. The 2400-0600 h period produced the largest number of walleyes of the four time periods, while the 1800-2400 h period was the most productive for rainbow smelt. The largest catches of walleye and rainbow smelt came during the 1200-1800 h period in the Williston Area. There was a positive relationship between walleye and rainbow smelt during the 1800-2*100 h and 0600-1200 h periods. Ten age classes were found for the total walleye catch. Age classes III and VII were the largest for the total walleye catch. There were few age I and II walleye caught. The weight-length relationship for all of the walleye was explained by the equation: log W = - 5.793 +■ 3.299 log L. The mean coefficient of condition for the total walleye catch was 1.0*4. The walleyes caught in the Van Hook Area had significantly higher condition factors than did the other two areas. Rainbow smelt was the only forage species that was identified in the walleye stomachs. The stomachs of walleyes caught in the 11-20 ft range contained the greatest number and volume of rainbow smelt per stomach.

Area morphometry, water temperature, light penetration and prey density are factors which may explain the larger numbers and faster growth rates of walleye caught in the Van Hook Area. The large catch of walleyes in the 0-10 ft range appear to be related to water temperature. Year class strength of walleyes is apparently closely related to water levels during spawning. Walleyes probably feed heavily on rainbow smelt because they are abundant, soft-rayed and easily caught.

Download

Share

COinS