An extreme high tide hits the shore, killing many crabs. When the weather calms, there are only a few blue crabs, but most of the red crabs are still there. Which mechanism of evolution best describes this scenario

The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process. 

Copper and gold have a high electrical conductivity