Pond Boss Forums INTRO Questions & Observations Cormorants and fish in ponds

There's been mention of Cormorants on here a few times, and what they can do to a pond. Here's my observations:

I recently completed a Fyke Net survey on a .8 ac pond. Visibility is 16"-18" due to high nutrient loading and an phytoplankton bloom. This survey was done over a 4 day period. There are LMB, BG, BH, Goldfish, Tilapia and Golden Rainbow Trout in the pond. The trout were stocked in October, the Tilapia are stocked annually to control FA (and do a tremendous job).

Water temps are currently between 79 and 80 degrees, dissolved oxygen is very high - it has a Vertex aeration system in it, plus a surface agitator. Surface O2 levels are over 11 mg/l and at the pond bottom they are in the low 9 mg/l range. The trout, even in the warm water, are still alive and active.

Between 2 and 5 Cormorants have been observed on the pond in the past 30 days on a daily basis. They are chased off when seen on the pond, but they return an hour later. There is also a Great Blue Heron that is a regular visitor to the pond.

The first day of the Fyke Net survey, there were 17 15”-18” Trout, roughly 500 3”-8” BG, 38 4”-9” BH, and 30 5”-7” Goldfish in the net. The amount of fish that were in the net that has signs of escaping from the cormorants was amazing. One trout, 8 BH, 11 Goldfish and between 70 to 80 BG showed signs of being grabbed but escaping. Only one Goldfish and 3 BG showed signs of being hit by the GBH and escaping.

The next 3 days of the Fyke Net survey showed roughly the same percentage of fish being hit but escaping from the cormorants. One 8” BG had its gill flap almost completely ripped off, and a few goldfish and BG were missing eyes.

I was surprised at how many damaged/injured fish are in the pond just from less than ½ dozen cormorants in water that has pretty poor visibility.