Emersion and thermal tolerances of three species of unionid mussels: Survival and behavioral effects

We evaluated the behavior and survival of unionid mussels after emersion in air temperatures across a range that is likely to be encountered during st atus surveys or relocations. Five laboratory tests were performed with pock etbook Lampsilis cardium Rafinesque (2 tests), pimpleback Quadrula pustulos a Lea (1 test), and spike Elliptio dilatata Rafinesque (2 tests) mussels, e ach conducted in a completely randomized, nested experimental design. For e ach mussel species (except Q. pustulosa), treatments tested included two wa ter temperatures (25 and 10 degrees C), five air temperatures (ranging with in +/-20 degrees C of the water temperature), three aerial exposure duratio ns (15, 30, and 60 min), and a no emersion control. All treatments were dup licated, with 10 organisms per emersion time and aerial exposure temperatur e (n = 320 mussels per test). Behavioral response (ability to upright) and mortality were measured daily for 14 d postemersion. Both water and aerial exposure temperature (air shock) were important predictors of times to firs t uprighting. The intensity function of first uprighting differed among spe cies (P < 0.01), and there was a significant interaction between E. dilatat a versus the other species and water temperature (P +/- 0.01). Over-all mus sel survival after emersion was high (93%); however, E. dilatata experience d significant treatment related mortality at the 25 degrees C test water, 4 5 degrees C aerial exposure temperature. Because of the high incidence of u prighting and survival of mussels in our study, emersion at moderate temper atures (15 to 35 degrees C) and durations (15 to 60 min) does not seem harm ful to mussels, and, therefore, conducting relocations and status surveys u nder these conditions should not impair mussel survival and over-all succes s.