A right of passage

Project Parore has the expertise to help landowners introduce and maintain good fish passages within their waterways.

Project Parore is hot on maintaining good fish passage. “We love our little critters,” says Project Parore General Manager Brodie Davis. “Little critters are also a key indicator of good stream health so it’s vitally important landowners check their streams for impediments to water flow.”

New Zealand has more than 50 species of native freshwater fish and several sports fish. Many of these species, like whitebait and eels, need to move between freshwater and the sea to complete their lifecycles.

Some also move upstream and downstream between different habitats in rivers and streams. For example, whitebait species (īnanga, kōaro and kōkopu) lay their eggs in freshwater, move downstream to the sea as larvae, grow into juvenile fish at sea, then travel back upstream where they grow into adults. It’s essential that they can move within waterways to reach these habitats and complete their lifecycle.

About 70% of our native fish are threatened or at risk. New Zealand waterways need to be carefully managed so native fish can access the habitats they need. If their movement is delayed or blocked completely, fish may not be able to complete their lifecycle. Their numbers can be reduced, or they may be completely lost from a stream.

Fish passage connects all the habitats that are necessary for freshwater fish and other instream organisms like frogs, shrimps and aquatic invertebrates, to complete their lifecycles.

Ensuring fish can move within, over and through physical structures, as well as managing the water quality and flow conditions in a waterway that may impede passage, are essential for healthy fish populations.

A stream should:

  • provide safe, easy up and downstream movement for all species and their various life stages
  • have different water conditions (like areas of fast and slow flow) and natural hiding places for fish
  • enable natural processes to continue, like sediment and debris moving downstream.

Barriers to fish passage

Culverts, weirs, fords, dams and tide and flood gates are common in waterways throughout New Zealand. If they are not designed, maintained and installed correctly, these instream structures can stop fish moving up and downstream and to the sea.

Disconnections between the water upstream and downstream of a structure can stop or slow down fish passage. This can be caused by culverts with a significant drop at the downstream end, extremely long structures, perched (undercut) structures, fast water flow through a structure and weirs that are too high for fish to navigate.

Some fish species are more affected by instream structures than others. For example, inanga are weak swimmers, whereas kōaro and baby eels can climb wet surfaces very effectively.

“If you have any of these challenges or disconnections on your streams which are affecting fish passage on your land, give us a call. Better still, send us a picture of the barrier so we can get a heads up,” says Brodie.

The Bay of Plenty Regional Council is also hot on looking after fish passage. “Regional Council is supporting Project Parore financially to help landowners fix fish passage issues.” Tools to mitigate some of these challenges include: fish friendly floodgates, culvert ramps, culvert baffles, mussel ropes, crawling mats and downstream landscaping. The FFG (Fish-friendly Floodgate) is a device that has been developed with funding and assistance from BOPRC and NIWA to address fish passage and water quality.

“Downstream landscaping is a very important link in this chain,” says Brodie. “This is often not considered but some species spawn in the banks of streams so it’s vital to consider the vegetation around stream banks. Again we can offer advice as to what to plant in these situations.”

Sediment loss and predators also affect both spawning numbers and fish passages. “You can see how interconnected and interdependent stream health and the whole ecosystem is.”

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