A school of sardines was found washed out between Saldanha Bay and Gansbaai, over the weekend.
The Department of Forestry, Fisheries and the Environment (DFFE) said fish kills also washed, about eight nautical miles offshore, near Hout Bay.
Zolile Nqayi, Spokesperson of the DFFE, said the first fish samples were collected on Saturday. In addition, the Department deployed scientific observers, to collect information on the distribution and extent of mortality.
Investigators will take into consideration an algal bloom, currently present at Saldanha Bay.
Nqayi urged members of the public “not to collect, handle or consume dying or dead fish found on beaches or floating about at sea.”