Publications: Research reports and publications

Towards revitalisation of toheroa in the Horowhenua

10 August, 2015
Cawthron Report 2756. Prepared for Taiao Raukawa and Manaaki Taha Moana.


Ngāti Raukawa ki te Tonga aspire to re-establish sustainable populations of toheroa on the Horowhenua coast, which was once famous for the abundance of this kaimoana. This report presents key approaches for revitalisation, and reviews the factors that should be considered in design of revitalisation activity and monitoring.

Three key approaches are explored for revitalisation of toheroa populations. These are natural stock regeneration, direct seeding from natural populations, and introduction of animals reared in artificial environments.

Attempts to achieve natural stock regeneration through harvest restrictions have been unsuccessful. Natural stock regeneration may occur if sufficient environmental management is undertaken (e.g. large-scale environmental restoration and restriction of beach access), but this is not practical at present. Smaller-scale environmental management activity that could feasibly be implemented in the short term (e.g., within ten years) would be insufficient to drive natural stock regeneration, but should be used to complement other revitalisation activity.

Reseeding of wild-caught toheroa could contribute to revitalisation programmes.

Translocation of wild-caught adults is more feasible than spat translocations. Adult translocations have succeeded in the past, have a high survival rate, and have the potential to contribute immediately to the reproductive output of the population. There are a number of risks associated with the approach, such as the vulnerability of adults to harvest, and survival over the potentially long distances the adults would need to be transported.

Culture techniques are developing for toheroa, and reseeding with spat reared in hatcheries should be considered as a future part of a revitalisation strategy. The introduction of hatchery-reared spat to the Horowhenua coast could offer benefits such as the potential for very large numbers to be reseeded, the use of locally-sourced brood stock, the need for fewer donor animals, and the absence of harvest pressure immediately after reseeding. While spat production techniques for toheroa are not yet fully developed, reseeding with hatchery-reared spat presents a promising approach for future revitalisation. Refinement of culture techniques should be encouraged so the use of hatchery stock can eventually reduce the pressure of translocation from wild populations.

Learning from revitalisation activity is particularly important in the case of toheroa: it is a taonga species and widely in decline, but there is a lack of understanding of the environmental factors that determine toheroa survival. The large gaps in knowledge of the toheroa lifecycle and ecology as well as its unsuitability to small-scale experimental reseeding, make a strong case for adaptive management. Monitoring information could feed back into the programme, so that management can respond to observed changes in toheroa populations and other environmental conditions.

In considering revitalisation of toheroa in a cross-cultural context, two key frameworks are presented. Firstly, the establishment of effective communication between the participant groups is required to ensure productive korero. The Te Kawa Whakairia model is a whare-based concept of communication. Under this framework, kaitiaki interact with a range of manuwhiri (such as scientists and councils) to ensure that priorities are understood and most effectively incorporated into revitalisation activity.

Additionally, an adaptive management framework is presented as a basis for programme design. This framework incorporates both knowledge and risk, and that provides a means for new information to be incorporated as the programme progresses. The knowledge gaps addressed in specific research projects, and information from monitoring would enable refinement of programme aims and strategies.

There is still much to be done before toheroa revitalisation activity can begin. While exploration of funding options is on-going, and brief consideration of funding requirements is presented, no financial resources are currently available to pursue this work.