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Keeping tabs on the new residents
ZEALANDIA Ecosanctuary

Keeping tabs on the new residents

Over the years, we've done a great job introducing different native wildlife to Zealandia – birds, fish, plants, you name it! But our job doesn't end there. After they settle in, we keep a close eye on them. Our Conservation team shares what goes down post-translocation. And trust us, it's more than you might expect! 

In case you haven’t heard yet, we are doing another translocation of toitoi/common bully this year. Last year, we brought in 160 toitoi from Kohangapiripiri, one of the two lakes at Parangarahu Lakes in East Harbour Regional Park. The ika/fish were released into Roto Māhanga, Zealandia’s upper reservoir. This little fish plays a big role in our freshwater ecosystem and helps the kākahi/freshwater mussel complete their lifecycle.   

For each translocation we carry out at Zealandia, we typically monitor introduced species for at least a few years post-translocation to make sure they settle in okay. Specifically, we keep an eye on the original individual’s survival and reproduction. For example, our post-translocation monitoring of the toitoi shows evidence of breeding and the population establishing at Zealandia.   

By knowing how many in original individuals survive and breed, we’ll have an idea of what our founding population for the sanctuary is like. This is important for the underlying genetic diversity of the population. For example, if we bring 60 birds to Zealandia but only 20 of them end up breeding and passing on their genes, the founding population would be 20, and would likely have low genetic diversity. This might mean we would consider doing a ‘top-up translocation’ of further individuals to reduce the loss of genetic diversity in the population.   

Our toitoi translocation project was already planned to be done in stages, both to reduce any impact on the Kohangapiripiri population and to ensure we have the space and capacity to provide the best care possible while the toitoi are in quarantine. We can only house so many fish at a time, and we need to be able to monitor them closely to ensure they are all well and healthy. Doing a series of smaller releases gives us the ability to do this.  

We will be collecting up to 600 fish all together from Parangarahu Lakes over three years. Releasing this number of fish over time will ensure that we have a strong, genetically diverse founding population. The more genetically diverse a population is, the more likely it can adapt and deal with threats like disease.  

Doing post-translocation monitoring is important not just for the management of the species in Zealandia but can also illuminate learnings useful for future translocations of different species. For example, post-release monitoring could indicate how suitable the new habitat was for the species: Does the new area provide all the resources that the species needs? Are there issues with the species dispersing outside the protected area? Is the new species being outcompeted by another already established species? As we’ve said before, conservation in Aotearoa New Zealand is a learning process, and we are constantly changing what we do based on new information.   

After translocation, one important question to ask is when do you stop post-translocation monitoring? The answer will depend on the species in question, how they seem to be settling in, any issues that may be arising that you need to keep an eye on, as well as the resources available to continue the monitoring. For some  species, we have ceased intensive monitoring but keep a general eye on them in other ways, e.g. through 5-minute bird counts. For other species like kākā and kākāriki, we have scaled back monitoring substantially, but may still do some limited monitoring for other purposes (e.g. to keep a subset of the population banded for research purposes, or as part of providing additional nest sites if not enough may be available in our relatively young forest).   

Want to be part of this game-changing work of re-establishing native fish species? You, your family, your workplace, or your community group are invited to sponsor a fish’s journey to Zealandia!   

Photo: Toitoi / common bully. Credit: Alton Perie

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