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Managing our Freshwater Ecosystem

The approaches and methodology for managing our freshwater ecosystems, are progressing rapidly. We should be proud of recent advances in this area and the continual movement in the right direction. But are we leading the way in this regard, or just following the flow of the rest of the world? 

Vegetation assessment using drone

Auckland Council senior ranger Matt Maitland overseas the fish transfer at Tawharanui by volunteers

The introduction of 10,000 giant kokopu (Galaxias argenteus) into Tāwharanui Regional Park was marked as a “giant milestone for whitebait” and could be a real asset in reducing the decline in this whitebait species. However, fish stock introduction isn’t new, they are already undertaken throughout the world to maintain local freshwater fisheries. Arguably the reason for the delay in using this technique to boost whitebait populations, has been the difficulty in mastering the breeding of whitebait in captivity. However, the question of why it took so long to master this process, (when the species have not only conservation value, but commercial value as well), still remains.

Recently Ecology New Zealand has been working on a site that has a degraded and modified freshwater ecosystem. As part of mitigation for the site, a stream channel that has been straightened and deepened to assist in draining the land, needs to be restored to compensate for lost stream further up the catchment. Standard stream restoration methodology would include riparian revegetation with three to five years of maintenance, then leaving the area to develop naturally, with the hope that it will begin to re-meander and develop a diverse stream channel morphology. This diversity of physical characteristics is important because more diverse habitat conditions support a greater range of species and age classes than simple habitats. Habitat diversity can also mediate biotic interactions such as competition and predation. Another alternative to achieve this diversity, is to undertake an expensive earthwork programme to re-meander the stream which the client, on this project, is unlikely to undertake. However there is one solution, that is often over looked in New Zealand that enhances the stream channel and kick-starts the meandering and stream channel diversification. This process is as simple as installing faggots or woody debris. Yet when you google for something as simple as “faggoting in New Zealand streams” there are no example projects detailing information like: which native woods are suitable, branch sizes, if dead non-natives are suitable. As such, this project would be a trial of a tested methodology, adapted for New Zealand. The installation will test the wood from a variety of species to see which is suitable for New Zealand's waterways.

UAV flow path analyse

Cross section view of installed faggots designed for one of Ecology New Zealand's project

For now, we are playing “catch up” with some of the leaders within freshwater management, but there is no reason we cannot lead in the long term. We need to take those risks and try tested international approaches under New Zealand conditions, and Ecology New Zealand is keen to push these developments. Of course, methodology will need to be adapted to suit New Zealand’s unique natural environment, but we are more than capable of undertaking the challenge.

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