Baby barracouta wash up dead from River Derwent after chasing bait fish
Thousands of dead fish have washed up on the shores of the Derwent Estuary in southern Tasmania.
It is believed the juvenile barracouta had been chasing bait fish up the river before becoming stranded in fresh water when the tide receded.
The fish have washed up near Lawitta and Millbrook Rise jetty.
Christine Coughanowr from the Derwent Estuary Program said there had been two separate events.
"We think schools of barracouta are swimming up stream on a rising tide, probably chasing bait fish," she said.
"Then when they get to the top of the Derwent, they're getting trapped in fresh water."
She said once the tide recedes the seafaring fish die in the fresh water.
"So basically they're in the wrong place in the wrong time," she said.
"They can't cope with the fresh water and they can't swim downwards because of the poor water quality at the bottom of the river."
She said the water at the bottom of the river is poor quality during the summer months.
"It's a stratified part of the river where you have fresh water that's lighter that floats on top denser, salt water," she said.
"At that point in the Derwent the salt water tends to have low oxygen levels."
Similar incidents occurred in the same area in 2011.
