Fish abundance
In each of the different treatment sections, fish were sampled using
minnow traps with carp bait. The traps were placed for 3 to 7 days in
each section of the ponds, and wet weight of the collected fish (g WW)
was measured. Total weight of fish per trap per day was used as a
relative measure of fish abundance (\(\theta\): catch per unit effort).
When no fish were collected, we set \(\theta\) =1. Note that shading may
have affected on number of fish collected by the traps. In this case,
CPUE can be viewed as a measure of fish activity and therefore an
indication of predation rate (Hairston 1987).