Parker was sentenced to preventive detention in August.
Mr Le Prou said the case gave people the confidence to come forward and Northland Police had received other complaints of sexual abuse since.
Assault, harassment and threatening behaviour, and breach of violence or non-violence restraining orders all increased.
Mr Le Prou said police were focused on holding offenders to account for all forms of violent or threatening behaviour.
"We recently produced, in conjunction with the Northland District Health Board, a DVD that tells the story of Whangarei woman Patricia McGrath, who died as the result of violence and the effect it had on her family and friends."
Mr Le Prou hoped the DVD would encourage violence victims and friends and neighbours to report incidents.
Dealing, cultivating and manufacturing illicit drugs decreased. Other offences to decrease included robbery, which was down by 27.4 per cent; burglary, down by 4.6 per cent; and theft, down by 6.1 per cent.