I aha ki ngā toheroa nō Horowhenua, what happened to the toheroa of the Horowhenua?
Authors:   , Thomson Tessa 
Published: February 2024

<p><strong>The toheroa (Paphies ventricosa) is a large suspension-feeding intertidal surf clam endemic to the sandy beaches of Aotearoa [New Zealand]. Toheroa are considered a taonga species (a concept similar to cultural keystone species) to the indigenous people of Aotearoa, Māori. My iwi [tribe] Ngāti Tūkorehe, and more widely Ngāti Raukawa ki te Tonga of the Horowhenua region, have a deep relationship with the toheroa and have suffered through the decline of the toheroa population and wish it could return to historical numbers.</strong></p><p>The concept of the pūtahitanga, which is the convergence or intersection of mātauranga Māori [Māori knowledge] and western science, framed as mātauranga supported by the tools of western science, was used for this study of toheroa.</p><p>To begin the investigation into the Horowhenua population of toheroa, semi-structured interviews were completed with my whānau [extended family] to obtain an understanding of the importance of the toheroa, collection practices, and the key observations whānau made regarding the decline of the species in the Horowhenua. The loss of the toheroa in the Horowhenua was upsetting to Māori, and it resulted in the loss of cultural practices and identity. There is a great desire to revitalise toheroa populations and remind people of what the toheroa means to our whānau.</p><p>Fisheries surveys were conducted of the toheroa populations on the Horowhenua coast between 1965 – 1977. Data from these surveys, and others, were extracted from reports and compared to assess trends in the overall population numbers and individual sizes of the toheroa on Horowhenua beaches. Toheroa populations declined to relatively small numbers by the end of the survey period. Using this population data, analysis of the decisions made regarding toheroa management for the Horowhenua beaches suggest that population numbers were not enough to support open-take seasons up to 1979, which could have further reduced the population to levels unable to support a future sustainable population.</p><p>To assess the current status of toheroa populations on the Horowhenua coast, three studies focused on Kuku Beach were conducted. First, an adult and juvenile population survey was completed. No adult toheroa were found at Kuku Beach, however, undetermined juvenile Paphies species were found, as well as populations of the ghost shrimp (Biffarius filholi).</p><p>Second, a larval survey was conducted as well as larval dispersal modelling to understand how toheroa larvae potentially move within and among populations across Aotearoa. Modelling indicated that larvae remain in the populations they are released from, which suggests that the Kuku Beach population cannot be re-seeded by larvae from larger populations that exist elsewhere. Finally, sampling of water and sediment for eDNA was conducted. An eDNA protocol for detecting toheroa was developed, however, no clear conclusions could be made from this investigation, but the approach shows future promise.</p><p>Using the findings from this study, and previous studies, the future of toheroa on the Horowhenua coast are discussed using the whakataukī [proverb] “kia whakatōmuri te haere whakamua”, which translates to “I walk backwards into the future with my eyes fixed on my past”. What needs to be done to revitalise the toheroa in the Horowhenua was outlined, and why this is important for generating positive outcomes for the species and the relationship that people have with this taonga.</p>