Brook charr alevins alter timing of nest emergence in response to chemicalcues from fish predators

Brook charr (Salvelinus fontinalis) lay their eggs in gravel nests called r edds. The nests are not defended for extended periods and the eggs and youn g may be subject to predation from predators that travel through the substr ate into the redd. In this study we tested whether long-term exposure of br ook charr eggs, to chemical cues from predatory sculpins (Cottus cognatus) resulted in an adaptive shift in the timing of emergence of charr alevins f rom artificial redds. We reared brook charr eggs in the presence of chemica l cues from sculpins fed brook charr eggs, sculpins fed brine shrimp,and a well water control. Significantly more alevins emerged during the first wee k of the emergence period when exposed to chemical cues from sculpins fed e ggs than from cues from sculpins fed brine shrimp or from well water. Alevi ns that emerged sooner were smaller and possessed larger yolk sacs than ale vins that emerged later in the emergence period. Our results suggest that a levins that emerge sooner may escape predation in the redd, but may pay a c ost in being under-developed upon emergence into the open water of the stre am or lake.