The long term skill shortage list does give an indication of the occupations where there is a sustained and on-going shortage of high skill workers both globally and throughout New Zealand. New Zealand Immigration also provides an Immediate Skill Shortlist and a Construction and Infrastructure skill shortage list.
Careers New Zealand Skill Shortages page is organised by shortages in different industries.
What is important is knowing if this industry is needed in Northland in particular. Contacting businesses and asking about opportunities or looking for vacancies will give an indication of the demand within the district.