High temperatures have been blamed for the deaths of hundreds of fish in two south coast waterways.

The Department of Primary Industries is investigating the fish kills at Meringo, near Moruya, and Wallagoot Lake at Tathra.

Greens Candidate for Bega Will Douglas at Meringo Lagoon inspecting the dead fish.

It is believed low water levels were the cause of hundreds of dead fish at Meringo, while a combination of low oxygen levels, high water temperature and changes to the salinity caused by recent rainfall led to mass deaths of fish at Wallagoot Lake this week.

NSW Upper House MP David Shoebridge reported hundreds of dead bream, eels, mullet, fingerlings and prawns were found in the saline coastal lagoon near Moruya, which is intermittently closed to the ocean.