"I was horrified to hear that this incredible animal was attacked in this way," Visser said.
"I've spent hours with Owha and there is absolutely no excuse for someone to do this."
Despite concerns about Owha's welfare they had decided not to intervene because of the risks involved for the seal during capture and sedation. They would continue to monitor her for any chance in her behaviour or body condition.
Owha is short for her name "He owha nā ōku tūpuna", which translates to "treasured gift from our ancestors", received from Auckland hapū Ngāti Whātua Ōrakei.
Leopard seals are a native species and protected under the Marine Mammal Protection Act 1978. .
Anyone charged under the act with harassing, disturbing, injuring or killing a seal faces a maximum penalty of two years' imprisonment or a fine to a maximum of $250,000.
A young leopard seal was killed after it was shot in the face in 2018 on a Northland beach.
Four teenage males, two aged 16 and two aged 15, were referred to Youth Aid over the incident.