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lots of fish swiming superimposed on whitebait fritters
(Image composite: Getty/ Finnbar Lee. Design by Archi Banal)

ScienceSeptember 24, 2023

Your whitebait fritter still holds mysteries for scientists

lots of fish swiming superimposed on whitebait fritters
(Image composite: Getty/ Finnbar Lee. Design by Archi Banal)

It’s whitebait season, but there’s a lot more to these unique native fish than what you see on your plate. 

In spring, when the tide is high, a miracle happens. Underneath the water, clinging onto grasses and rushes, small beads burst open, and larvae wiggle out. As the tide drains, they are carried by the current, smaller than a fingernail clipping, out into the wide wide sea. 

This is how the life of īnanga, one of five whitebait species, begins. “They’re amazing fish,” says scientist Finnbar Lee, a researcher at the Cawthron Institute. “I think people would appreciate them more if they knew about their amazing life cycle of going to sea and returning to rivers.” 

a hand with a stribey little brown fish on in
A banded kōkopu: as they’re active at night, they are difficult to photograph, Lee says. (Image: Finnbar Lee)

There are lots of things people know about īnanga and their other relatives in the galaxiid family, a type of freshwater fish found throughout the Southern Hemisphere. We know they’re delicious, for one: during the whitebait season, which is happening right now, the translucent white larvae can be found (for a hefty price tag) sizzled with eggs (also expensive) and seasoned with lemon. They’ve been a source of food for humans for a long time. Māori have caught and eaten these fish for hundreds of years, using flax nets and drying them so they would last. 

After being washed out to sea – a way for the larvae to save energy, since swimming is tiring when you’re tiny – the migratory galaxiids … hang out and eat zooplankton? While it’s clear that they’ve grown a lot by the time they return to freshwater a month or two later, this part of their lifecycle is mysterious. This is partially because tiny almost-clear fish are hard to spot in the vastness of the ocean. “We have no idea what happens at sea,” Lee says. “We presume they’re eating zooplankton and phytoplankton – the sea is a resource-rich environment where there’s lots of food, so that is one reason to have the larvae there.” While migratory galaxiids don’t have natal homing, like salmon, meaning they don’t necessarily return to the rivers they came from, the mysteries about their marine life cycle mean it’s hard to tell where there are separate populations of the fish, and therefore they are harder to manage. 

two hands holding a fish with long strong fins for going up streams
The kōaro, or climbing galaxias, has strong fins for climbing up rocks and waterfalls (image: Finnbar Lee)

While predation is normal, there are also human-created threats to the pattern of life the migratory galaxiids have assumed over thousands of years. The unpredictable effects of climate change are an obvious one, Lee says. Will rising water temperatures, as we’ve seen in marine heatwaves around Aotearoa, make the fish’s metabolism faster, meaning they have to eat more or else return to the rivers skinny? How will sea level rise impact where eggs are laid? Will changing patterns of rainfall alter the kōkopu species, which lay their eggs in gravel and wait for a flood? “If you lay your eggs in the air and the flood doesn’t come, the egg runs out of food and dies,” says Lee, and I imagine thousands of hungry little beads, waiting for water that will never arrive. 

New Zealand whitebait numbers are now in decline and with several species being threatened, calls are increasing to revise and tighten whitebait fishing regulations around the country (Photo: Hagen Hopkins/Getty Images)

Introduced species are a threat, too. Laying eggs in gravel was historically a good strategy since it reduced the risk of predation, but there’s some evidence that rats and mice like to eat the eggs before they get a chance to hatch. Sleek brown introduced trout, joy of fly fishers, munch on the īnanga and kōkopu, too. Habitat damage doesn’t help: while councils are now mandated to make culverts and drains that fish can navigate, fish can accumulate in the ponds beneath pipes, trying in vain to get to the cool alpine headwaters they thrive in. “You see pools of fish, trying to get up, but they can’t,” Lee says. 

Community efforts have made a difference to the whitebait species, as well as the non-migratory galaxiids. “There are lots of people doing restoration at different levels,” Lee says. Riparian planting, which creates dappled shady habitats in the water and reduces the amount of sediment in the water, helps; so does providing hay bales for the fish to lay eggs on where there aren’t enough of the grasses they like. Lee says that improving rules around how much fertiliser and sediment gets into freshwater catchments will make a difference, since cloudy and algae-filled water is not a nice home for fish.

Native galaxiids will soon have a voice in parliament in Lan Pham, a freshwater ecologist with a high list ranking for the Greens, who loves these “critters” so much that she had several attend her wedding (in a tank). 

a man in a green shirt with a tree in the background
Scientist Finnbar Lee says there’s a lot more to learn about galaxiid species (Photo: supplied)

But at the moment, there is science to do too. “Whitebait are a fishery, but there’s a lack of data about the species,” Lee says. “They move between the rivers and the sea, which makes it hard to collect data: we don’t know what the populations are doing.” It seems like one whitebait species, the giant kōkopu, is naturally rare – but is it actually the case that its population has declined? Radically changed ecosystems make it hard to assess how many fish the rivers really can support. As an ecologist, Lee could make a guess, but with so much missing information “it could be orders of magnitude wrong.” Reducing how many juveniles are taken out by whitebaiting could improve the outlook for these species – but given how many other factors play a role, it also could not. 

The tides turning on migratory galaxiids mean that some people object strongly to eating whitebait, because these animals are not just at risk, but also integral participants in a whole ecosystem. Farming the fish is one alternative, with commercial operators entering the market.

Lee, at least, has caught the bug (just like galaxiids, who feed on invertebrates). “On holidays with my family, when we stay at an Airbnb by a stream, I always bring my headtorch and a few nets,” he says. At night, when the fish are active, he goes to look for them, to catch them and have a look. There they are: silvery īnanga bellies, banded kōkopu’s electric stripes, speckled giant kōkopu blending in to the stream bed. Then he lets them go.

“I think they’re fabulous, they’re stunning fish,” Lee says. “Kōaro, the climbing galaxias, can climb up vertical surfaces with their pectoral fins, they go up waterfalls to get to mountain streams, they’re amazing.” With so many threats, and not enough data, protecting the species is vital. “It would be a disaster, an absolute disaster, if we lost them.”

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