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).