The covering of an enti re pool by the water fern not only affects the fish populations but I have recorded an entire change of events from the fish eagles in the air to the freshwater mussels on the bottom of the pool. Birds such as Cape wagtails feed on these insects. Freshwater crabs crawl along the surface hunting for food and then quickly burrow into the fern when disturbed. Even water leguaans of 40cm in length can walk over this thick mat. Starting at the top, fish eagles and kingfishers will not be able to locate fish in the pools and have not been observed since the water fern became established.
Otters also have difficulty finding their pre y.
It is interesting to note that now, after our continuous removal of the water fern over several years, an otter has reappeared at the pool. The otter appears to be mainly eating freshwater mussels and possibly can not locate freshwater crabs in the Azolla . Waterfowl, such as black ducks, yellowbill ducks and Egyptian geese used to frequent the pool and now are only rarely observed if some of the pool is not covered. The fern must reduce the amount of area for the waterfowl to raise their young. Domestic animals have ventured onto the water fern in farming areas, possibly thinking that it was a solid sur face, and have drowned.