They crawled out due to a drop in oxygen levels, Western Cape Fisheries Department spokesman Lionel Adendorf was quoted as saying.
It was unknown whether they came out on Friday or Saturday.
Adendorf said authorities were collecting the surviving lobsters and placing them in unaffected waters.
The broadaster reported that the drop in oxygen levels was caused by an ‘algal bloom’ which stretched around 80km along the west coast.
Adendorf said the algal bloom or red tide was a natural phenomenon that was likely to stay until May.