Fish Kill Report Card

Aquatic Plants

Macroinvertebrates

Black Bream

Waterbirds

Fish Kills

Water Quality

Major fish kills have been recorded in the Vasse estuary since 1905 with large fish kills reported every 5-10 years. Fish kills are usually caused by low dissolved oxygen and/or phytoplankton species that are toxic to fish. Fish kills grades are outlined below.

2023 Fish Kills Grade

A

Key Findings

No fish deaths have been recorded in the last 2 years.
Fish deaths in the Vasse Wonnerup wetlands occur most often in the Vasse Channel, and upstream of the floodgates.
Low dissolved oxygen is the cause of most recent fish kills in the Vasse Wonnerup Estuary, often associated with an algal bloom.

The most recent fish kill in June 2020 killed an estimated 20,000 black bream and 5,000 mullet, and was caused by a late season algal bloom causing low dissolved oxygen levels in the Vasse Estu-ary Channel.

Fish Kills Grades Over Time

Year	Month	Grade
2023		A
2022		A
2021	June	E
2020		A
2019	May and December	E
2018		A
2017		A

Grades

Excellent

Very Good

<100

Fair

100-999

Poor

1,000-5,000

Very Poor

>5,000

Estimated number of fish deaths

Fish Kill Report Card

Aquatic Plants

Macroinvertebrates

Black Bream

Waterbirds

Fish Kills

Water Quality

2023 Fish Kills Grade

A

Key Findings

Fish Kills Grades Over Time

Grades

View other report cards

Aquatic Plants

Macroinvertebrates

Black Bream

Waterbirds

Water Quality