Lake Itasy is located 10 km south-east of Analavory and 25 km north-west of Soavinandriana. It is a freshwater crater-lake with marshy areas in its southern and eastern parts, lying within a steep-sloped volcanic massif. It is permanent, with seasonal variations in the water-level, having an average depth of 4 m but reaching up to 10 m at its centre. The Andranomena and Mariandrano rivers feed the lake in the east, while the Lily river flows out of the lake. The lake receives a lot of sediment from the rivers and from the eroded adjacent slopes. There is marginal vegetation of reedbeds Phragmites and clumps of Cyperus (up to 2 m), and floating mats of the non-native water-hyacinth Eichhornia. Submerged plants include Ceratophyllum and Potamogeton. Near the middle of the lake, there is dense vegetation of various very tall aquatic plants.
See Box and Tables 2 and 3 for key species. Forty-four species are known from the lake, of which 10 are endemic to Madagascar. The dense vegetation near the middle of the lake is a refuge for herons (Ardeidae) and rails (Rallidae). A locally resident population of Anas melleri is probably of national importance. Ardea humbloti is infrequently recorded.
BirdLife International (2020) Important Bird Areas factsheet: Lake Itasy. Downloaded from http://www.birdlife.org on 09/04/2020.