Effects of water temperature on the mortality of field-collected fish marked with fluorescent pigment

The cumulative effects of collection, handling, and marking with fluorescent pigment on the mortality of adult minnows, young-of-the-year centrarchids, and large centrarchids and percids was determined at five water temperatures (10-20.6 degree C) in field trials. There have been few field trials of this type. The mortality of centrarchids and percids was directly related to temperature and decreased noticeably when the temperature was below 19.5 degree C. The mortality of minnows decreased somewhat as river temperatures cooled but was always at least 50%. Variation was high in the temperature-related patterns of mortality in different taxa and sizes of fish. This variation complicates the accuracy and usefulness of pigment in marking field-collected fish for mark-recapture studies in warmwater systems.