Judge Michael Crosbie said Harris and his associate had taken the rock lobster "under the cover of darkness'' using torches and turning off their vehicle's lights to avoid detection.
He said it was vital to denounce such offending and for Harris to realise fishing was only allowed in certain areas.
"There are 44 marine reserves in New Zealand, representing less than 1% of New Zealand's marine environment. Marine reserves are there for a purpose and there are plenty of other places to legitimately get crayfish."
Harris was sentenced to a total of 200 hours' community work on all three charges.
He was disqualified from driving for six months on the disqualified driving charge, and charged $130 court costs on the disqualified driving and Marines Reserve Act charges.