The Mortality and Growth of Marked and Unmarked Lake Trout Fingerlings in the Presence of Predators

Abstract

Abstract Two experiments were conducted between October 4, 1948, and October 25, 1949, at the State Fish Hatchery at Marquette, Michigan, to determine the effect of predation on fin-clipped lake trout, Cristivomer n. namaycush [Walbaum], fingerlings. One experiment involved 4,000 unmarked fish and 4,000 clipped fish confined in the presence of adult brook trout, brown trout, rainbow trout, and lake trout. In a smaller experiment, another pond was divided by a fish-tight screen and bulkhead. In the lower half, weighted brush piles were added to provide cover. The upper half was left without cover. Into each half of this pond 500 unmarked fish and 500 marked fish were released, along with various predator fish. The small experimental pond was covered with chicken-wire screen to prevent bird predation. Observation of deaths caused by factors other than predation, plus the counts of survivors at several examinations revealed the numbers of fish lost to the predator fish between various dates. Chi-square analy...