Action: Provide refuges for fish within ponds
A controlled cross-over trial in the UK found that great cormorant Phalacrocorax carbo foraging success was lower in a pond with artificial refuges, compared to a control pond.
Supporting evidence from individual studies
In Berkshire, England, a controlled cross-over trial (in the winters of 2003 and 2004) found that great cormorant Phalacrocorax carbo foraging success was lower in a pond with artificial refuges (Russell et al. 2008), compared to a control pond (on average, 67% less fish weight consumed/cormorant visit); fish loss was significantly lower (79% less fish weight lost); and there were 77% fewer cormorant visits. Two adjacent ponds (45.0 x 27.2 m; 1.35 m depth) were used, with provided in one pond each year. Refuges were 12 mesh covered cages (2 x 2 x 1.2 m high) in two blocks of six, with shade cloth and containing 4-6 tree saplings to provide cover. At commencement of each trial, ponds were similarly stocked with freshwater fish. Fish weight was recorded at the beginning and end of each trial.