POPULATION STUDIES OF FOUR SPECIES OF MOLLUSCS IN THE MADISON RIVER, YELLOWSTONE NATIONAL PARK1

摘要: Population statistics were calculated for natural populations of Physa gyrina, Gyraulus deflectus, Valvata humeralis, and Pisidium compressum. Total net production model was within 10% the value graphically. Data showed a generally good fit to curve. The average two methods determining total annual gastropods 5.150 g/m2. Assuming an efficiency 0.25, gastropod assimilation approximately primary production. Growth rates apparently not limited by food supply. Mortality highest in spring summer lowest winter with principal causes predation loss during high water. Reproductive periods Physa, Gyraulus, extended from fall; reproduction largely August.