September 30, 2013 at 11:51 pm #539MikeKeymaster
The Swan River Trust does not know why more than 32,000 fish died in
the Swan River this week.
Experts say they know what killed the fish – another Karlodinium
micrum algal bloom – but they don’t know why.
High levels of the algae proved fatal for blowfish and gobble guts
around Como Beach and Matilda Bay this week, but similar levels
recorded earlier in upper parts of the river did not kill fish.
Swan River Trust environment manager Jane Latchford said something
had made the algae toxic.
Some algae bloomed after hot weather but Karlodinium micrum seemed to
flourish in a range of temperatures, Dr Latchford said. In this
instance it had affected shaded shallow areas near the river’s edge.
Only blowfish and gobble guts died, probably because they were the
species most likely to be living in the shallows where the algae
bloomed. Bream and herring had yet to move down the river from the
upper reaches and avoided the new bloom.
Karlodinium micrum levels were between 20,000 and 70,000 cells per
millilitre of water at the recent fish kill sites. Generally, 10,000
per millilitre is considered safe and Dr Latchford said scientists
grew concerned when they reached 50,000. This year, levels upstream
had been recorded at up to 100,000 per millilitre with no fish kills.
Last year, up to 100,000 fish were killed by algae in the Swan River.
Dr Latchford said similar kills were likely for the next five to 10
years. The trust warned that people and pets should avoid contact
with dead or dying fish.
The forum ‘Strange Animal Deaths’ is closed to new topics and replies.