But a Niwa research team hopes to find new ways to help make the New Zealand delicacy’s tricky journey easier.
They begin life as eggs laid in vegetation beside streams in late summer, and when the eggs hatch, they are carried downstream as larvae and spend about six months at sea before migrating back upstream as whitebait in spring, to grow into adult fish.
On their journey, they face a range of issues in our waterways, including man-made barriers such as dams, weirs and culverts that prevent them reaching their preferred freshwater habitats.
Hamilton-based hydroecologist Dr Eleanor Gee and her team have rigged up a series of experiment ramps — each with different angles and a mix of smooth and textured surfaces.
The aim is to test how adept the fish are at making their way to the top of the ramps, and simulate their upstream migration.
She is using young fish of the whitebait species koaro and banded kokopu, and plans to move on to redfin bullies.
"These species are known to be climbers and all migrate as part of their life cycle.
"What we’re trying to do is find out the limits of the known climbing fish, by testing them on ramps of varying steepness.
"Ultimately, we’d like to look at whether larger or older fish find it more difficult.
"We know some small fish can climb near vertical slopes, but they probably can’t do that their entire lives, so we want to find out at what stage they stop."
Dr Gee said it was important to find as much as possible about climbing so they could be managed in the best possible way.
"Koaro and banded kokopu use an alternating limb movement, like swimming freestyle, while bullies go for a bilateral movement which is more like breast-stroke, moving both limbs in the same direction at the same time.
"It’s pretty impressive watching them shuffle their way up these structures.
"They can also climb a long way, with some known to surmount significant waterfalls, depending on the steepness and the type of substrate available."
Dr Gee hoped the insights from the experiments would be used to update the New Zealand Fish Passage Guidelines which were introduced in 2018.
The guidelines set out the recommended practice for designing infrastructure in streams that enable fish to pass through, and were developed to help waterway managers, engineers, environmental officers, iwi and communities understand and implement better management of fish passage in New Zealand.
New freshwater management rules require all regional councils to identify barriers to fish passage, and come up with a plan for mitigating them.
