Monitoring
How has marine reserve status helped the sea life in the area? DOC is monitoring the changes in the Long Island-Kokomohua Marine Reserve to measure the changes over time.
Blue cod have increased in size and
numbers inside the marine reserve
Monitoring commenced in March 1992, approximately a year before the marine reserve was established. Monitoring has continued annually including:
- Blue cod catch (rod/line) measure and release (all years except 2001).
- Catch per unit effort (line fishing) for various finfish species (all years except 2001).
- Underwater fish counts from rubble and macroalgae habitats in most years.
- Rock lobster density, size and sex in particular years (including all years since 2001).
- Size and density of key invertebrate grazers (paua, kina and cats eyes) in some years.
Key monitoring results include:
- Blue cod were significantly larger and more abundant within the marine reserve compared to neighbouring control sites. In particular, very large blue cod (>330 mm) are now much more abundant in the reserve compared to fished areas.
- Over the duration of the study, the average size of blue cod in the reserve increased initially and has remained consistently higher than the control sites. Mean blue cod size has either declined or fluctuated widely at the controls.
- Blue moki are now larger within the marine reserve compared to fished areas outside the reserve.
- Rock lobsters within the reserve significantly increased in abundance after 2001, and were significantly more abundant compared to control sites from 1999 onwards. In 2009, lobsters were 3.3 times more abundant in the marine reserve compared to fished sites outside the reserve.
- From 2001, rock lobsters in the reserve have been significantly larger than those found at control sites. In 2009, large lobsters (>115 mm carapace length) represented 45% of the total reserve population, compared to 18% in fished areas.
- Lobsters, blue cod and blue moki are noticeably less wary of humans in the reserve compared to sites outside of the reserve.
- Larger size classes of paua (especially paua >130mm) are now present within the marine reserve compared to fished sites.
Very small kina (<50 mm) were absent from all reserve sites in 2008, but were otherwise present at all reserve and control sites throughout the study. This result perhaps indicates a predator/prey response to the marine reserve (ie. small kina are being preyed upon by blue cod and lobsters), however, further monitoring will be needed to verify this hypothesis.