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Kukuriki Reef Intertidal Ecology Survey 2025

A Rūnanga-led project documenting the marine biodiversity of a culturally significant reef in north Taranaki

01

Prepared by

Jesu Valdes, Lead Scientist, Taranaki Regional Council

02

Reviewed by

Fern Kumeroa, Taiao Team Te Runanga o Ngāti Mutunga

03

Community Participation

18 whānau members and community representatives attended the survey

Introduction

In 2018, SLR Consulting NZ Limited was engaged by OMV Taranaki Limited to undertake a marine ecological inspection at Kukuriki Reef, a site culturally important to Ngāti Mutunga in north Taranaki. Ngāti Mutunga selected this reef due to its significance as a mahinga kai site, particularly for kuku/kūtai (New Zealand green-lipped mussel; Perna canaliculus).

The initial intertidal assessment was carried out on 25 November 2018 during spring low tide, with Ngāti Mutunga whānau present to select the reef location. This qualitative survey identified species present and developed recommendations for future monitoring as part of Ngāti Mutunga's annual environmental monitoring programme.

1

2018

Initial qualitative survey by SLR identifies 19 species

2

2019

SLR report recommends quantitative monitoring approach

3

2025

First quantitative survey using TRC methodology finds 26 species

Taking these recommendations into consideration, a quantitative intertidal ecological survey following Taranaki Regional Council's rocky shore method was conducted on 6 November 2025 as part of Ngāti Mutunga's coastal Mauri Compass programme. This work supports Ngāti Mutunga's aspirations to provide for their relationship with the coast and ensure coastal resources are restored and protected.

Taranaki Coast Marine Environment

Rocky reefs dominate the intertidal zone of the Taranaki coastline. Around the ring plain, these reefs are largely formed from lahar (volcanic derived) materials consisting of andesite cobbles and boulders bound within an ash-type matrix. Selective erosion of the weaker matrix leaves harder cobbles and boulders to form large platform reefs.

Although typically low in relief, these reefs can be considerable in extent. The reefs off the Waitara coastline extend as far as five kilometres offshore. Most intertidal reefs are comprised of lahar conglomerate bedrock, andesitic boulders, rock pools and occasional sand patches.

Complex Habitat

Rocky shores provide three-dimensional environments with cracks and crevices offering shelter for numerous marine species

High Energy

Exposed to persistent south-westerly winds from the Tasman Sea and dominant westerly waves

Dynamic Conditions

Considerable sand movement and turbid conditions from river inputs and cliff erosion

Kukuriki Reef

Kukuriki Reef is located approximately 2 km southwest of the Waiiti Beach Camp. It is the only rocky feature in an otherwise sandy beach, with a backdrop of large papa and sandstone cliffs along the upper shore. Large numbers of NZ green-lipped mussels (P. canaliculus) are present on the reef and harvested by Ngāti Mutunga and the wider local community.

Unique Characteristics

  • Very small reef confined to limited area
  • Bound by sand on either side
  • Significant mussel bed coverage reaching up to 100% in some areas
  • Different from other Taranaki reefs in size and composition

Figure 1 Location of Kukuriki Reef in relation to Waiiti Beach Camp (source: SLR, 2019)

Intertidal Ecology Survey Method

Taking into consideration SLR's 2019 recommendations, the quantitative intertidal survey method used by Taranaki Regional Council was selected. This robust methodology is widely used by regional councils throughout Aotearoa as part of State of the Environment (SoE) Monitoring.

Site Selection

Transect location identified using GPS coordinates and reference photographs to ensure repeatability

Transect Setup

50m transect laid parallel to shore at approximately 0.6m above chart datum

Block Establishment

Five 5m x 3m blocks established along transect with five random 0.5m² quadrats per block

Species Assessment

Percentage cover estimated for algae and encrusting animals; individuals >3mm counted and identified

The rocky shore component of the SoE monitoring programme for Taranaki was initiated in 1994/95 and has continued annually since. Six representative reef sites are surveyed twice yearly in spring and summer.

Survey Implementation at Kukuriki Reef

Survey Details

  • Date: 6 November 2025
  • Time: 17:00 NZDT
  • Low Tide: 0.28m at 16:53
  • Weather: Fine with light offshore breeze
  • Total Quadrats: 25 random samples

The survey area was selected by Ngāti Mutunga, focusing on areas with significant healthy mussel beds while excluding taller vertical reef formations.


1

Start Rock

NZTM E:1726494 N:5689163

2

Transect Direction

Parallel to water line, 50m length

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End Rock

NZTM E:1726470 N:5689121

The method previously described was applied to Kukuriki Reef for the first time on 6 November 2025, marking the beginning of long-term quantitative monitoring at this culturally significant site.

Ecological Indices

Survey data are used to calculate two key ecological indices: species richness and the Shannon-Wiener diversity index (H'). Species richness is a straightforward count of the total number of different species in a particular area.

Shannon-Wiener Index

This mathematical tool combines both richness and evenness (the relative abundance of each species) into a single number. The value increases as both the number of species and the evenness of their populations increase.

Greater Shannon-Wiener Index = Greater diversity

100%

High Diversity

Many species in even proportions

50%

Moderate Diversity

Some species dominance

25%

Low Diversity

Few species or one dominant

Diverse ecological communities are composed of a high number of species present in relatively even proportions. These communities often include a high number of species within each functional group (primary producers, grazers, suspension feeders, predators) and are generally more resilient to stressors and disturbances.

Understanding Diversity and Sand Impact

High Diversity Communities

Composed of many species in relatively even proportions, with representatives from multiple functional groups. These communities show greater resilience to environmental stressors.

Low Diversity Communities

Characterized by fewer species or where one species is disproportionately abundant. These communities may be more vulnerable to disturbances.

Sand Cover Threshold Effects

While reef communities may tolerate some level of sand cover, above a certain threshold the community becomes impacted. Once this threshold is exceeded, the number of species declines before eventually reaching low values at high percentages of sand cover.

Studies in Taranaki have demonstrated that sand cover is the main driving force behind variability in species richness and diversity at a site.

Survey Results: Species Discovery

26

Total Species

Found during 2025 survey

12

Algal Species

Including green, brown, and red algae

14

Animal Species

Including barnacles, gastropods, and bivalves

+37%

Increase

From 19 species in 2019 to 26 in 2025

This survey showed a significant increase in the number of species identified compared to SLR's 2019 report, which found 19 species total (4 algal and 15 animal species). The 2025 survey using TRC's quantitative method identified 26 species (12 algal and 14 animal).

Green Algae

3 species of Chlorophyta including sea lettuce and gutweed

Brown Algae

3 species of Phaeophyceae providing habitat structure

Red Algae

6 species of Rhodophyta including coralline paint

Animal Species Diversity

Invertebrate Groups Found

  • Barnacles (3 species): Beaked, columnar, and plicate barnacles
  • Gastropods (3 species): Radiate limpet, spotted whelk, cart-rut shell
  • Bivalves (2 species): Green-lipped mussel, little black mussel
  • Chitons (3 species): Giant, snakeskin, and rainbow chitons
  • Other: Blue tube worm, pillbox crab, orange sponge

Dominant Species

NZ green-lipped mussel (Perna canaliculus) was the only abundant species, with 41-100% coverage

Present Species

All other algal and animal species were classified as present (<50 individuals or <20% coverage)

The lowest number of species found in surveyed quadrats was zero, occurring when sand coverage was 100%. The highest number observed in a single quadrat was fourteen species.

Ecological Parameters at Kukuriki Reef

The survey data revealed important patterns in species distribution and diversity at Kukuriki Reef. Mean values per quadrat showed moderate sand coverage and relatively low species richness compared to other Taranaki reefs.

Algae Diversity (H')

0.387 ± 0.300

Animal Diversity (H')

0.194 ± 0.247

Combined Diversity (H')

0.328 ± 0.324

Comparison with Regional Reefs

For comparison, the rocky shore sites monitored by Taranaki Regional Council as part of State of the Environment monitoring show much higher values for ecological parameters. Data from six sites studied between 1994 and 2024 provide important context for understanding Kukuriki Reef's unique characteristics.

Kukuriki Reef presents significantly lower values than all six TRC monitoring sites, reflecting its unique environmental conditions and limited habitat availability.

Discussion: Method Effectiveness

Survey Success

This survey method proved effective at providing quantitative data on species richness and diversity at the mussel beds area of Kukuriki Reef. It successfully trialled the methodology utilized by Taranaki Regional Council at other rocky reefs in the region for the first time at this culturally significant site.

Focused Approach

The 2025 survey concentrated efforts on one area of outcrops significant to Ngāti Mutunga due to stable mussel beds

Increased Detection

More time spent in the mussel bed area resulted in identification of 26 species versus 19 in 2019

Standardized Data

Quantitative method allows detection of changes and trends if repeated annually

The increase in species found (from 19 in 2019 to 26 in 2025) can be explained by the difference in methodology. The 2019 survey searched a wider area without a standardized approach, while the 2025 survey used TRC's quantitative method for a more targeted search.

Understanding Kukuriki's Unique Environment

When comparing ecological parameters to TRC's State of the Environment monitoring sites, Kukuriki Reef presents significantly lower values. This was expected due to the coastline and reef area being restricted by habitat and susceptible to sand influence from being a highly exposed coastline.

Limited Substrate

Restricted papa and sandstone outcrops provide limited habitat for hard-substrate dependent species

High Exposure

More exposed and erosion-prone than other Taranaki reefs, facing persistent wave action

Sand Impact

High sand deposition causes scour and burial, reducing diversity through physiological stress

Lower Diversity

Fewer species can survive in these challenging conditions compared to more sheltered reefs

Highly heterogeneous sites like Mānihi Reef, characterized by a wide range of different substrates with plenty of cobbles, rocks, and boulders, present a wider range of habitats for species to colonize and inhabit, resulting in higher species richness and diversity values.

Sand Effects on Reef Communities

Sand deposition has been shown to have profound effects on intertidal hard-shore communities in Taranaki. The presence of high quantities of sand results in reduced diversity due to two primary mechanisms: sand scour and temporary sand burial.

Sand Scour

Impacts reef organisms causing removal from substrate, physiological stress, and increased metabolic demand

Sand Burial

Results in reduced light, oxygen and food availability for buried organisms

Community Impact

Inundation events cause significant reductions in species richness and diversity

47.6%

Mean Sand Cover

At Kukuriki Reef

100%

Maximum Coverage

Zero species found

Studies by Walsby (1982), Airoldi et al. (1996), and Howse et al. (2000) have documented these effects. Sand scour and burial create challenging conditions that only the most resilient species can tolerate, explaining the lower diversity observed at sand-influenced sites like Kukuriki Reef.

The Role of Green-Lipped Mussels

Despite the challenging conditions, the pockets of hard substrate created by remaining papa and sandstone outcrops provide important habitat. The NZ green-lipped mussel was found to be the most abundant species, forming dense beds in the surveyed area.

Habitat Creation

Mussel beds provide structure for other species

Water Filtration

Filter feeding improves water quality

Food Source

Provide nutrition for predators and scavengers

Resource Control

Structure environment and resource availability

Protection

Offer shelter from wave action and predation

During the survey, several species were found living amongst (cart-rut shell) or on the mussels (columnar barnacle), demonstrating the mussel beds' importance as habitat providers in this limited reef environment.

Habitat Comparison: Kukuriki vs Mānihi

Kukuriki Reef

  • Limited papa and sandstone outcrops
  • Surrounded by extensive sand
  • Low substrate heterogeneity
  • Fewer habitat niches available
  • Mean richness: 5.56 species/quadrat

Mānihi Reef

  • Wide range of substrate types
  • Abundant cobbles, rocks, boulders
  • High substrate heterogeneity
  • Multiple habitat niches
  • Mean richness: 20.16 species/quadrat

The stark difference in habitat complexity between these sites explains the variation in species richness and diversity. Highly heterogeneous sites present a wider range of different habitats for species to colonize and inhabit, supporting more diverse communities.

Substrate Diversity

More substrate types = more ecological niches = higher species diversity

Habitat Stability

Stable substrates support permanent residents and complex food webs

Acknowledgements

We extend our sincere thanks to Te Rūnanga o Ngāti Mutunga for inviting us to participate in this activity as part of their coastal Mauri Compass mahi, and to all whānau who attended.

We acknowledge and greatly appreciate the manaakitanga, kōrero, and commitment shown, not only through participation in the rocky shore survey methods used by Taranaki Regional Council, but also through the sharing of experiences and mātauranga Māori.

Partnership

Collaborative approach combining scientific methodology with cultural knowledge and values

Community Engagement

Active participation from 18 whānau members and community representatives

Future Collaboration

Building and strengthening relationships for ongoing environmental monitoring

This was a highly valuable activity, and we look forward to continuing to build and strengthen this relationship through future monitoring and conservation efforts at Kukuriki Reef.

Recommendations

Taking into consideration the results from SLR's 2019 report and this quantitative ecological survey carried out for the first time in 2025 at Kukuriki Reef, the following recommendations are made for ongoing monitoring and management:

1

Annual Monitoring

Ngāti Mutunga undertakes a survey in the same location following this methodology once per year as part of long-term monitoring at Kukuriki Reef

2

Reference Library

Build up a reference library with clear, high-resolution species photos from different angles of each animal and algae found in quadrats

3

Trend Analysis

Continue to estimate ecological metrics of species richness and diversity to compare parameters over time and detect trends and changes

4

Mussel Bed Mapping

Conduct aerial imagery and/or mussel bed mapping regularly to detect changes in the extent of mussel coverage at Kukuriki Reef

Safety and Timing Recommendations

Tidal Requirements

Schedule surveys only for tides ≤0.3m during favorable weather conditions, as the area is exposed for a brief period

Weather Conditions

Do not attempt monitoring if adverse weather conditions are present such as strong onshore winds or large swell

Tidal Window

Consider safe return time to Waiiti Camp when planning survey duration

Personal Protective Equipment

  • Appropriate footwear for rocky terrain
  • Diving gloves to protect hands
  • Sun hat and sunscreen
  • Additional change of clothes
  • Adequate hydration supplies

References

Primary Sources

  • Airoldi, L., Fabiano, M., Cinelli, F. 1996. Sediment deposition and movement over a turf assemblage in a shallow rocky coastal area of the Ligurian Sea. Marine Ecology Progress Series 133: 241-251.
  • Howse, B.P.S., Black, K.P., Cole, R.G., & McComb, P.J. 2000. Port Taranaki Dredging consent renewal studies. Report 3: The relationship of sediment flux to abundance and sizes of pāua and kina on New Plymouth reefs. Department of Earth Sciences, University of Auckland.
  • SLR, 2019. Kukuriki Reef Intertidal Inspection. SLR Ref: 740.10004.00400‐R01. Version No: ‐v1.0.

Regional Council Reports

  • Taranaki Regional Council. 1991. Taranaki Coastal Marine Area, Resource Description and Management Issues. Taranaki Regional Council, Stratford, New Zealand.
  • TRC, 2025. Rocky Shore State of the Environment Monitoring Report 2019-2024 Technical Report 2025-34.
  • Walsby, J.R. 1982. Marine ecological baseline programme NZSFC Synthetic Petrol Plant Motunui.

Appendix I: Algal Species Identification Guide

This identification guide provides visual references for the 12 algal species found during the November 2025 survey at Kukuriki Reef. Clear photographs from multiple angles assist with accurate species identification during future monitoring.

Codium fragile

Common name: Dead man's fingers
Type: Green algae (Chlorophyta)
Characteristics: Spongy, finger-like branches

Coralline Paint

Type: Encrusting red algae
Characteristics: Pink to purple crust covering rock surfaces

Gelidium caulacantheum

Common name: Jellyweed
Type: Red algae (Rhodophyta)
Characteristics: Small, branching red fronds

Ulva sp.

Common name: Sea lettuce
Māori name: Rimu
Type: Green algae
Characteristics: Bright green, sheet-like

When photographing algae for identification, capture the full specimen showing fronds and holdfast from multiple angles. Include a scale reference when possible.

Appendix I: Animal Species Identification Guide

This section provides visual references for the 14 animal species found during the survey. Accurate identification requires clear photographs from both dorsal (top) and ventral (underneath) views for gastropods and other mobile species.

Perna canaliculus

Common name: NZ green-lipped mussel
Māori name: Kuku/Kūtai
Abundance: Abundant (41-100% coverage)
Significance: Ecosystem engineer, culturally important

Cellana radians

Common name: Radiate limpet
Māori name: Ngākihi
Characteristics: Distinctive radial pattern on shell

Chamaesipho columna

Common name: Column barnacles
Māori name: Tiotio/Koromaungaunga
Characteristics: Tall, columnar shape

Plaxiphora obtecta

Common name: Giant chiton
Māori name: Haka-hiwihiwi
Characteristics: Large, eight-plated mollusk

Appendix II: Additional Identification Resources

The following resources provide comprehensive identification guides for marine species found in New Zealand's intertidal zones. These are valuable references for building identification skills and confirming species during surveys.

Rocky Shore Guide – Northern NZ

University of Otago comprehensive guide to northern New Zealand rocky shore species

Download PDF Guide

NIWA Identification Guides

Series of specialized guides covering specific taxonomic groups:

  • Adorable Anemones
  • Beloved Barnacles
  • Coastal Crabs
  • Beautiful Browns (Brown algae)
  • Splendid Sponges (Intertidal & Subtidal)
  • Super Sea Slugs

iNaturalist NZ

Community science platform for recording and identifying New Zealand biodiversity

Visit iNaturalist NZ

Moving Forward: Long-Term Monitoring

This inaugural quantitative survey at Kukuriki Reef marks the beginning of a long-term monitoring programme that will track ecological changes over time. The baseline data collected in 2025 provides a foundation for detecting trends and assessing the health of this culturally significant site.

1

2025 Baseline

First quantitative survey establishes baseline data: 26 species, mean richness 5.56, diversity 0.328

2

Annual Monitoring

Repeat surveys detect changes in species composition, abundance, and diversity over time

3

Trend Analysis

Multi-year data reveals patterns and helps identify environmental stressors or improvements

4

Adaptive Management

Monitoring results inform conservation decisions and management strategies

Partnership Success

This project demonstrates the value of combining scientific methodology with mātauranga Māori and community engagement. The collaborative approach ensures monitoring is culturally appropriate, scientifically rigorous, and sustainable long-term.

1

Baseline Year

Foundation established

25

Quadrats

Surveyed annually

26

Species

Currently documented

Through continued monitoring and partnership, we can ensure Kukuriki Reef remains a healthy mahinga kai site for future generations of Ngāti Mutunga.