A helping hand for migrating fish

By Waiology 23/05/2014

By Paul Franklin and Sjaan Bowie

Many of New Zealand’s iconic freshwater fish species, such as whitebait and eels, undertake migrations between the sea and freshwater as part of their life-cycle. Whitebait, for example, lay their eggs in freshwater or estuaries before the larvae move out to sea after hatching (Figure 1). After a number of months growing at sea, they then return to our rivers and streams and migrate upstream as the whitebait that New Zealanders love to catch and eat in their whitebait fritters! The ones that escape the whitebait nets and make it into our freshwater streams grow into adults before beginning the cycle all over again (Figure 1). Unfortunately, these movements are increasingly being obstructed by man-made structures commonly found in our rivers and streams, such as culverts (e.g. Figure 2), weirs, tide gates and dams. These barriers can delay or prevent fish from reaching their habitats, contributing to the decline and loss of these fish in many of our waterways.

The whitebait life-cycle.
The whitebait life-cycle.

This year sees the first World Fish Migration Day on 24th May 2014. The aim of WFMD is to create global awareness of the need for open rivers and free routes for fish migration. More than 250 events are planned worldwide, starting here in New Zealand. For more information on the events in New Zealand visit the WFMD events page and check out the New Zealand WFMD Facebook page.

In New Zealand’s waterways, the Department of Conservation (DOC) and Regional Councils have specific responsibilities to manage fish passage under the Freshwater Fisheries Regulations 1983 and Resource Management Act (RMA) 1991, respectively. The regulations require that no structure should impede the passage of fish. However, there are still many poorly installed instream structures that restrict fish migrations and prevent fish from accessing critical habitats. For example, in the lower Waikato River it has been estimated that access to around 1100 km of tributary streams is restricted by tide and flood gates alone. That’s equivalent to a river running all the way from Auckland to Christchurch that fish can’t fully access!

An example of a fish migration barrier caused by a poorly installed culvert.
An example of a fish migration barrier caused by a poorly installed culvert.

With a high number of our freshwater fish species in decline, there is increasing concern about how migration barriers impact on their numbers and distribution. To address these concerns, in November 2013 around 90 experts from around the country met at a two-day workshop in Wellington to discuss how to improve the management of fish passage in New Zealand’s rivers. Some of the key themes that emerged from the workshop were:

  • A need to improve access to resources providing guidance on managing fish passage;
  • The requirement for research to fill gaps in our knowledge about fish and their ability to pass different structures;
  • The importance of installing fish passage solutions that meet best-practice designs; and
  • The need for greater collaboration between ecologists and engineers to find effective solutions for enhancing fish passage at instream structures.

To help achieve these aims NIWA and DOC have recently agreed to work together to collate and develop national resources to support fish passage management in New Zealand. This will include setting up a new multi-agency National Fish Passage Advisory Group that will be responsible for developing and promoting best-practice methods for enhancing fish passage. As part of this project, we are launching a new fish passage website on World Fish Migration Day with the aim of improving access to the most up-to-date information on what you can do to help our freshwater fish in New Zealand. You can also find copies of the presentations and proceedings from the 2013 Fish Passage Workshop.

Tackling the problem of fish migration barriers is a national challenge, but one that offers a potentially cost-effective opportunity for significant biodiversity gains in our valued freshwater ecosystems. It is important before you do anything to know what fish are present at a location, because in a few key places barriers can be protecting threatened native fish from invasive fish species. However, in the majority of places you can help our freshwater fish by:

  • Ensuring that structures in waterways are designed to allow for effective fish passage;
  • Removing old structures that are no longer required;
  • Working together to fix barriers and restore fish passage; and
  • Contacting DOC or your local Regional Council if you are concerned that an instream structure is creating a fish passage barrier.

Dr Paul Franklin is a freshwater ecologist at NIWA and Sjaan Bowie is a freshwater technical advisor at the Department of Conservation.

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