The Ecology and Food Habits of the Sculpin (Cottus beldingi) in Relation to the Eastern Brook Trout (Salvelinus fontinalis)

MASTERS THESIS: 1. The objective of this study was to determine whether the sculpin competes with trout for food and preys on their eggs and young. The study was conducted during the fall and winter of 1951-52. 2 Large sculpins survive better on bottoms of rubble and boulders. 3. Bottom dwelling aquatic insects constituted 99.4 percent of the sculpins diet. The chief foods of sculpins were the Diptera, Trichoptera, Ephemeroptera, and Plecoptera. The Diptera and Trichoptera were the important fall foods of sculpins. The Ephemeroptera were the important winter food of sculpins. Diptera were the principal food of sculpins less than 59 mm. 4. Sculpins larger than 80mm used the large nymphs of the Trichoptera, Ephemeroptera, and Plecoptera for food. 5. The average number of empty stomachs was greatest in December and more stomachs of small sculpins were found empty than large sculpins. The average volume for sculpin stomachs with food was greatest in February. The average number of food items eaten by sculpins decreased slightly between October and April. 6. Age groups . Were identified in a length frequency histogram constructed for the sculpins collected during October and November Maturing males averaged 85.0mm in length. Maturing females averaged 73.6 mm in length. 7 Eastern brook trout spawning did not begin at once in all sections of the stream but progressed gradually downstream. In the middle portion of the stream, spawning lasted from October 7 to November 7. Eastern brook trout nests were found mainly on the fringes of riffles. 8. As evidenced by this study, sculpins are not a serious predator of trout eggs or trout young. Eastern brook trout are an important predator of sculpins. 9. Sculpins compete with eastern brook trout for food. The aquatic foods eaten by eastern brook trout were the same foods eaten by sculpins. Consumption of terrestrial organisms and sculpins by eastern brook trout reduces food competition with sculpins. 10. Sculpins and eastern brook trout do not compete for shelter