Citizen Science Report
Kina Wellbeing Survey (Year One)
Each year, Te Kohuroa Rewilding Initiative (TKRI) carries out monitoring and surveying through citizen science to assess the impact of the kelp restoration program at Te Kohuroa Matheson Bay.
Several indicators are measured to assess changes in biodiversity and habitat resilience, including the presence and abundance of key species such as tāmure (snapper), kōura (lobsters), rimurimu (seaweeds) and kina (sea urchins).
Surveys are carried out by project volunteers to understand changes in the health of kina living in and around TKRI’s kelp restoration site.
In this report, we present a comparison between the results from the pilot program kina wellbeing surveys (2024/25) and the most recent surveys from year one of the program (2026).
Introduction
Figure 1: Kina (Evechinus chloroticus) wearing ‘hats’ to protect from predators.
Background
Kina are an endemic, taonga (treasured) species within Aotearoa. They typically live on coastal rocky reefs, within a depth range of 1-14m and are found close to their preferred food source, kelp. Kina are known to hide in cracks, and hold stones or shells (a behaviour called ‘hatting’) to protect themselves from predators. Along with several other species of sea urchin within Aotearoa, kina support healthy marine environments when they are part of a balanced ecosystem.
Kina are valued as kaimoana (seafood). Their roe (eggs) is traditionally harvested and consumed by Māori and other communities and, like most sea urchins around the world, it has a specific flavour relating to what they eat. Kina roe also has commercial value, and is sold to local and overseas markets. This means the quality and density of kina roe is important for both communities and commerce.
At Te Kohuroa Matheson bay, common kelp (Ecklonia radiata) is abundant and contributes to shallow water kelp forests and seaweed habitat. Over the last 50 years, kelp forests have been negatively impacted by trophic cascades (caused by overfishing), which in turn produces an overpopulation of kina and the formation of barren areas. Despite being able to live for over 20 years, kina within barren areas become sick and unhealthy due to a lack of food, and other environmental stressors. The citizen science process carried out through TKRI uses size, weight, and roe quality as an indicator of sea urchin and environmental wellbeing.
Method
Sea urchin health is commonly measured through a process called the Sea Urchin Gonad Index (GI). By measuring kina diameter, total weight, and roe weight, volunteers can calculate how much of a kina’s body weight is made up of roe. This provides insight into urchin health, and also indicates how suitable they are for harvesting as kaimoana.
Between 2024 and 2026, kina were collected during three community restoration events at the restoration site to measure population health. In the pilot program (2024/25) two sample sets were collected two months apart in November and January within the same summer season. In 2026 (year one of the program), only one sample set was collected in January due to weather disruptions. At each event, 50 kina were randomly selected from the harvest and measured based on diameter (cm), total weight (g), and roe weight (g). In addition, roe quality was tasted and judged by volunteers to determine how ‘edible’ they were, referred to as the taste quality metric. These measurements allowed comparisons over time to assess changes in kina size and condition.
Figure 2: Kina roe being carefully removed from the test (shell) for weighing. (Photo: Anne Basquin)
Results
Data from the three events in November 2024, January 2025, and January 2026 were compared to determine how kina size and roe weight changed over time.
Average kina diameter and total weight significantly increased in 2026 compared to both sets of data from the previous season (see Figures 3 and 4). Average kina diameter was 27% larger and average total weight was 34% larger in January 2026 than in January 2025.
Average roe weight decreased significantly between the pilot program and year one sample sets (see Figure 5). Kina roe measured in 2026 weighed an average of 28% less than the roe measured in 2025. The roe measured in 2025 weighed 42% less than the roe measured in 2024. However, there was no difference in the average roe taste quality metric between any of the measured dates.
Figure 3. Diameter measurements of 50 sampled kina on 3 event dates. Each dot represents one kina.
Figure 4. Total weight measurements of 50 sampled kina on 3 event dates. Each dot represents one kina.
Figure 5. Roe weight measurements of 50 sampled kina on 3 event dates. Each dot represents one kina.
Discussion
Why did only some kina measurements increase?
The significant increase in kina size and weight within the different seasonal sample sets shows a positive change in the population’s health dynamics within the restoration site. Kina rely on kelp as their primary food source. Since the first kina removals took place in 2024, evidence of kelp regrowth has been observed and photographed at several different areas within the restoration site, suggesting kina have had access to more nutrition over time. In addition, urchin density has continued to decrease due to seasonal volunteer removals, which has resulted in less kina and in turn likely less competition for food. Based on this citizen science survey, kina appear to be growing larger in response to an increase in their available food source and less competition.
This suggests kina are growing larger and more healthy in the restoration site as kelp regrows within the area, compared to smaller kina that was found when the area was barren. Giving kelp a chance to recover seems to have a positive effect on the species that rely on it as habitat and food.
The decrease in roe weight between November 2024 and January 2025, suggests that a significant amount of spawning may have taken place between these two dates. The Sea Urchin Gonad Index (GI) is primarily used to assess the reproductive maturity, size, and quality of sea urchin roe for research and commercial use. Different sea urchin species are known to attain high GI values in different months of the year, which is based on their breeding cycles and associated environmental factors such as water temperature.
The further decrease in roe weight during January 2026 suggests that the kina already passed peak spawning season. While larger urchins tend to have more roe, roe weight can vary based on factors like season and spawning cycles. Science suggests that rising sea temperatures may affect the spawning timing of kina, prompting an earlier release of eggs. Marine heatwave forecasting by NIWA predicted higher than normal sea temperatures at Matheson Bay in summer 2026. Since food availability and water temperature are the main factors that impact sea urchin GI variation, it is possible that higher than normal sea temperatures may have affected the 2026 kina data set and their overall GI result.
The ‘Yum to Yuck’ scale
Volunteer taste-testing showed an insignificant variation in the quality of kina roe from the restoration site between years and sample sets. Roe taste stayed fairly consistent between 2024-26 with little change in quality of flavour. Since the weight and quality of the roe were not related to kina size, these factors may not be clear indicators of kina health in this study. While the ‘yum to yuck’ scale can be used as an indicator of roe quality, it is not easy to record accurately across datasets. Unlike roe weight, flavour is subjective, and therefore taste-testing is a qualitative metric (e.g., based on an opinion) rather than a scientific one. In addition, the taste-testing process was not carried out by the same volunteer across datasets, creating a potential variation in measurement simply down to preferred taste. Reviewing roe edibility is valuable as an exercise for volunteers to understand how different kina can have different tastes and how that can change both seasonally, and due to environmental conditions.
Figure 6: Marine Scientist, Caitlin Blain, assisting citizen scientists with kina wellbeing measurements.
Conclusion
Since 2024, Te Kohuroa Rewilding has used kina harvesting as a community-led approach for kelp forest restoration at Te Kohuroa Matheson Bay. Since the first kina removals took place, evidence of kelp regrowth has been observed within the restoration site. Kina density has also decreased due to the voluntary harvesting of kina for kaimoana. Based on the citizen science surveys carried out, kina are growing larger in size, likely due to an increase in their food source and less competition due to a reduced population. Although roe weight decreased over time, this may reflect seasonal or biological cycles rather than long-term environmental health.
Community-led restoration appears to be supporting the temporary reversal of barrens and the increase of kina health at Te Kohuroa Matheson Bay. While community restoration can kick-start environmental change, it is not a permanent solution. Only the reintroduction of key urchin predators such as tāmure and kōura through reduced fishing and/or temporary or seasonal fishing bans, will help to rebalance the ecosystem.
Building effective restoration practices takes time, and there will always be factors that affect kina health that are not able to be influenced by community efforts. Therefore, future actions to monitor the health of the ecosystem are essential. Through continued data collection, project volunteers will help the community to better understand the positive impacts of the project’s rewilding action on the regeneration of the marine ecosystems.
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