Flow is the opposite movement of water against the flow of blood in the fish's gills.

Counter current flow is the opposite movement of water against the flow of blood in the fish's gills.

Its either a) or b),wind and water erosion gradually widen the canyon

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.