Cooke Aquaculture is attributing a recent mortality event at its salmon farm sites off Black Island in Maine to uncommonly low oxygen levels in the cages.

The fish are being disposed of per the company’s standard operating procedures and farm management plan, Joel Richardson, a spokesman for Cooke, said in a statement.

Richardson told IntraFish the company has not released information on the total number of fish that died in the incident or the size of the fish.