Abstract:
The Long Bay-Okura Marine Reserve (established 1995) is a 980-hectare no-take
reserve located on the North Shore of Auckland. This reserve is influenced by the urban
sprawl of New Zealand’s largest city through high sediment loads from coastal erosion and
development. It was established to “protect a typical slice of Hauraki Gulf”, but despite its
long protection, few investigations have explored the ecological benefits of this urban marine
reserve and how effective it is at protecting species within its boundaries. This thesis
examined the diversity of habitats in the reserve as well as the effect of 25 years of protection
on two taonga species.
To understand the current conditions of the benthic habitats and create a reference
point for future comparisons, subtidal habitats were mapped inside and adjacent to the reserve
using satellite and aerial imagery with geo-referenced drop camera images of the seafloor to
validate habitat categories. Subtidal reef made up 7% of the reserve and was largely covered
by canopy-forming large brown algae (Ecklonia radiata, Carpophyllum spp., Sargassum
spp.), whereas low relief reef was dominated by turfing algae (e.g. Corallina officinalis) and
high sand cover. Habitat composition was comparable inside and adjacent to the reserve.
Baited video surveys of reef fishes were used to evaluate reserve protection of
carnivorous fishes. As seen in other reserves in northern New Zealand, snapper (Chrysophrys
auratus) were substantially larger and more abundant inside, with no legal sized individuals
recorded in adjacent fished sites. Sea urchin (kina, Evechinus chloroticus) density and size
were evaluated to assess the potential for reserve effects, either increase (protection of fished
species) or decrease (via trophic cascades). Kina were generally larger and found at higher
densities within the reserve, suggesting benefits from protection in this area and harvesting
may have reduced densities on surrounding reefs. This contrasts patterns seen in other
reserves in the Hauraki Gulf.
Despite the degree of anthropogenic influence, Long Bay-Okura Marine Reserve
protects several commercially, culturally, and recreationally important species. This
demonstrates that reserves in urbanized areas can have significant ecological effects despite
degraded habitat due to sedimentation and stressors associated with urban areas.