A Department of Conservation (DoC) investigation has found the 41 fur seals found dead in Te Oka Bay near Christchurch died of natural causes.
Human interference was not to blame.
The seals were found last Sunday by a couple walking along the beach. The bodies were too badly decomposed to confirm the cause of death, but "human-induced mortality" could be ruled out, DoC's Christchurch operations manager Andy Thompson said.
A pathologist report stated there were no penetrating wounds or bruising.
The report says "it is possible these pups had died in a colony nearby and been washed up at Te Oka Bay in the large swells that occurred in a series of storms," Mr Thompson said.
It is believed the seals died in early July.
The most likely cause of death is heavy seas pounding the colony. At the time the seals were young and vulnerable, and couldn't escape the waves.
DoC staff will continue to monitor the area for any unusual events that affect large numbers of seals.
Around 8,500 seals live and breed in the are,a and there is a population in New Zealand of more than 200,000.
Newshub.
