A celebration of fish migration
Saturday 24 May is World Fish Migration Day, a subject close to the hearts of Horizons Regional Council’s freshwater
management team.
The Horizons Region is home to 17 species of native freshwater fish and over the past few years Council staff have been
working in partnership with landowners, engineers, Horowhenua District Council, NZTA and the Ministry for the
Environment to help these fish move freely through waterways.
Freshwater management officer Anna Deverall is new to her role but has already been part of work to install 8 fish
passes and 3 fish-friendly floodgates within tributaries of the Manawatū River.
“Many people don’t realise the diversity of fish life that inhabits our rivers and streams, but once you get talking to
people they’re often keen to find out more.
“Some of our native fish are really good climbers, others aren’t as good. We’ve been working with our engineering team
to determine the best solutions for the rivers and streams where fish passage is compromised by culverts or flood
protection works,” she says.
The Horizons team have walked a lot of rivers from the mainstem back up to their source to try and locate any barriers
and prioritise them for fixing.
“Basically there’s no point in fixing a downstream barrier if there’s another one upstream,” Ms Deverall says.
“Further down the track we’ll measure the effectiveness of fixes to the barriers to check whether they’re working and
continue our learning around what works for different species.”
Five different native fish species make up the whitebait catch and over 90 percent of those caught are inanga. The
remaining species are koaro, giant kokopu, banded kokopu and short jaw kokopu.
Ms Deverall describes inanga as diadromous, meaning they spend half their lifecycle at sea with the other half spent in
freshwater.
“Adult inanga lay their eggs in the dense long grass along stream banks during high tides in February and March. These
eggs hatch during the next high tides and larvae are carried out to sea.
“In the springtime, juvenile inanga make their way back upstream where those lucky enough to escape the whitebaiters’
nets grow to become adults and repeat the cycle.
“If you find whitebait crawling up the side of the bucket holding your whitebait catch, please consider releasing these
as they are koaro; the rarest of our whitebait species,” she says.
Other native fish species found in the Horizons Region include: dwarf galaxids, brown mudfish, redfin bully, bluegill
bully, lamprey, common bully, giant bully, torrentfish, smelt, longfin eel and shortfin eel. Many of these species can
be viewed at Te Manawa as part of its Te Awa exhibition.
Measures put in place to help these fish swim freely in rivers and streams range from baffles created using rocks and
mussel rope for fish to climb up, to weighted flood gates installed in areas where traditional flood gates are
restricting fish movement. Ms Deverall says the chosen solution is largely dependent on fish species, in-stream
environment and the type of obstruction.
Horizons’ State of Environment report released in 2013 shows maps of sites where native fish have been found. It states
that while additional populations of rare and threatened species were discovered during a survey in 2011, predictive
modelling suggests there should be significantly more native fish in significantly more sites.
Ms Deverall hopes that increased awareness around native fish species and their migratory patterns in conjunction with
work currently underway will see populations increase over time. The Council is running a colouring competition around
World Fish Migration Day to aid this awareness.
Copies of the colouring competition are available from the Horizons website or by contacting Horizons’ environmental
educator or freshwater team on toll free 0508 800 800. There are three age categories for entries: under 6, 6-9 and
9-12. Winners will receive native plants for their homes or schools.
Horizons will also feature a different fish on its Facebook page over the next couple of weeks, providing an opportunity
for people to find out more about each species.
“Our native fish are pretty special but once they’re gone they’re gone forever. World Fish Migratory Day is a good
opportunity to raise awareness and get people thinking about the significance of our Region’s rivers and streams as
native habitats,” Ms Deverall says.
ENDS