The Water Corporation has defended the environmental safety of lower Lake Kununurra after residents raised concerns over the number of dead fish seen there last week.
The level of the lake is lowered annually so the corporation can perform a routine inspection of the dam wall and carry out essential maintenance to the levee bank.
Discovery Holiday Park manager Mark Powell said he accepted the maintenance work needed to be done, but questioned if it could be done with more sensitivity to the environment.
"Last year when they cleared trees from the levee bank we picked up hundreds of dead or maimed bats in the park," he said.
Mr Powell said he had never seen such a big fish kill, adding it could not just be a natural kill from the fish being forced through the Lake Argyle spillway.
Water Corporation North West regional manager Rino Trolio said in previous years the organisation had cleared a small number of exotic tree species along Lakeview Drive as part of planned maintenance work.
He said the trees needed to be removed because their roots damaged the flood levee bank, and he was not aware of any impact on wildlife this year or in previous years.
"During the maintenance work, Lake Kununurra is kept at 45 per cent capacity to minimise impact on wildlife in the lake," he said.
"This allows fish to migrate to Lake Kununurra from the diversion dam.
There are strict licensing conditions and procedures.
"These identify any potential impacts on wildlife and ensure appropriate controls are put in place to minimise any impacts of our work."
Mr Trolio said the Water Corporation began refilling the lake on Saturday and it returned to its normal operating level by Monday.
"We were able to repair significant damage to the Kununurra diversion dam levee bank and complete all essential maintenance one week ahead of schedule," he said.