Huon Aquaculture Group has warned of a big drop in full-year earnings and a material impairment and asset write down after a deep and sustained dive in salmon prices.

The warning on low prices came on top of a triple-whammy first half where Huon was hit by fish losses through a fire that melted pens, fish escaping through a big tear in another pen and allegations of stealing by a group of employees that have resulted in criminal charges.