Petuna Aquaculture has become the latest Australian salmon farmer to report increased mortalities as a result of higher water temperature this summer.

The company's farm in Rowella, Tasmania, experienced a temperature spike in an unusually short time frame, followed by a prolonged period of long, hot days, reports the Australian Associated Press.

It is unclear how many fish have died, but Tasmania's Environment Protection Authority (EPA) director Wes Ford reportedly said the number is in the thousands.

He said higher temperatures started about a week ago and increased mortality "progressed over the course of the last seven days."