A right of passage
Katikati’s 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 in the stream 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 life-cycles. New Zealand waterways need to be carefully managed so native fish can access the habitats they need.
Some also move upstream and downstream between different habitats in rivers and streams. For example, whitebait species (ı¯nanga, ko¯ aro and ko¯ kopu), 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 ie passages to reach these habitats and complete their lifecycle.
About 70 per cent of our native fish are threatened or at risk. If their movement up and downstream is delayed or blocked completely, fish may not be able to get to the habitats they need to complete their life-cycle. 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 downstream organisms like frogs, shrimps and aquatic invertebrates, to complete their life-cycles.
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.
In order to do this, 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 and enable natural processes to continue, such as sediment and debris moving downstream.
The Regional Council is supporting Project Parore financially to help landowners to tackle their fish passage issues.
BARRIERS TO FISH PASSAGE
Culverts, weirs, fords, dams and tide and flood gates are common in streams and rivers. If they are not designed, maintained and installed correctly, these 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. Fish can also be sucked into water intakes if they don’t have suitable fish screens or are not designed to keep fish in the waterway.
Some fish species are more affected by in-stream structures than others. For example, inanga are weak swimmers, whereas ko¯ aro whitebait and baby eels can climb wet surfaces very effectively.
Project Parore has the expertise to help land owners introduce and maintain good fish passage within their waterways.
“If you have any of these challenges and or disconnections on your streams which are affecting fish passage on your land come and see us and we can arrange to come and take a look. Better still, send us a picture of the barrier before you come so we can get a heads up,” says Brodie.
The Bay of Plenty Regional Council is also hot on looking after fish passage. “The Regional Council is supporting Project Parore financially to help landowners to tackle their 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 important 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 passage.
“You can see how interconnected and interdependent the whole stream health and eco-system is.”
A pilot study was conducted to investigate inanga spawning success in the Uretara and Te Mania streams from April to June 2022. The study was carried out by researcher Rae, Hee-Yun Jung.
Check out the following link on the Project Parore website for the full report. https://projectparore.nz/inangaspawing-success/