Smith-Dunlop said the seal will also go after bait on fishing lines when people are not around to feed it, which could result in fish hooks getting stuck in its mouth.
Kekeno also posed a risk to humans.
"Kekeno will bite if they feel threatened, and the bacteria in their mouth can cause quite nasty infections."
DoC's recommendation was that people stay at least 20m away from seals. They can inflict serious injuries to humans and dogs.
There was expected to be an influx of keneko pups and juveniles appearing on land until the end of September as they wean from their mothers.
DoC takes a hands-off approach when it comes to seals, because they are resilient and will normally find their way home if given time and space.
However, DoC rangers will intervene if the kekeno is in notably poor condition, immediate danger, tangled in debris, causing disruption or being harassed by people or dogs.
If people are worried about a seal being in danger, injured or harassed by people or dogs they should call the emergency hotline 0800 DOC HOT (0800 362 468).
It is an offence to disturb, harass, harm, injure or kill a seal. Dog owners can be prosecuted if their dog attacks a seal.