When you sneak past locals lingering on a smoke break and into a ravine next to an aging general store, you don’t expect to begin a hunt for a rare fish.

“Most of the streams along the Hāmākua coast that I apparently supported the people of ‘o’opu, “wrote Tim Grabowski, director of the Hawaii Cooperative Fishery Research Unit US geological surveyin an email about where the fish in question is. The problem is that, despite dozens of streams lining this 80 km long, winding, picturesque coastline, very few – if any – are open to the public.

So I crept down the precariously steep and muddy path into a canopy of green leaf to one of the most discreet and least obstructed access points. Here the rural Hawaiian landscape is transformed into wild nature; Wind and the rumble of pick-ups crossing the bridge are replaced by moisture, gnawing mosquitoes, and a babbling brook.

“‘O’opu are pretty easy to spot with decent polarized sunglasses,” Grabowski said. Yet not a single fin creature moved when it reached the creek and looked into the clear brown water.

‘O’opu – the Hawaiian word for fish in the goby family – mostly refers to several species of unusual freshwater fish that navigate inland waterways, some by climbing the islands’ waterfalls with their mouths and suction cup-shaped, fused pelvic fins. Four types of gobies and one type of sleeping goby (a family related to gobies but lacking the fused pectoral fin common to all gobies) make up the only true freshwater fish on the remote island chain. Scientists say ‘o’opu are largely endemic, understaffed, and threatened by development around their natural stream habitats.

These fish are small, modest, and usually brown and camouflaged, spotted, or striped (although the male of a species, ‘o’opu’ alamo’o, is a notable exception as it can be half black and half light orange during spawning season). . And each species seems to prefer a specific habitat along the length of a creek, with the most impressive adult waterfall climbers preferring the most secluded and inland pools.

With more than 200 cm of annual precipitation, the green Hāmākua coast of the island of Hawaii drips from waterfalls. North of east-facing Hilo, it is on the youngest of the major Hawaiian islands. Only around 500,000 years have passed since it emerged from the sea. This region is the steep rear of majestic Mauna Kea, the highest mountain in the world at 10,211 m as measured from its underwater base. The volcano looks like a huge wall in the open ocean. The only surface against which clouds collide after more than 4,000 km nothing but the Pacific Ocean towards west of Mexico. Here the streams are steep and short and prone to flooding.

Only five native species of ‘o’opu evolved to tackle Hawaii’s ragged mess of freshwater currents, and four of them developed the remarkable ability and drive to climb.

Even so, Grabowski said, “Hawaiian freshwater fish are very under-discussed. There isn’t much in the literature on ‘o’opu, and there are still many aspects of its basic biology and ecology that are largely unknown.” What scientists know, however, is fascinating.

They kind of jump out of the water and cling to the side of the falls

“They’re jumping out of the water, so to speak, and clinging to the side of the falls,” said Richard MacKenzie, a water research ecologist with the Pacific Southwest Research Station, Part of the US Forest Service. “Then they roll up the waterfall in short bursts of energy, usually at the edge of the stream.” Like other fish in their goby family worldwide, the pelvic fins of the fish are fused into a suction cup. The Hawaiian fish use their suction and scratchy mouths to scrape algae off rocks, drag themselves onto rocks in rapids, and continue upstream to steep vertical cliffs.

Adjustment, separation

How far any of the four species of climbing fish goes up and inland from a stream appears to be related to their adult size. “The largest ‘o’opu,” Grabowski said, referring to’ o’opu nākea (Awaous guamensis), which can grow to a foot long – “may not get over the lower reaches of most of the streams.” As you continue inland and uphill, larger species disappear and the smaller fish dominate.

While juvenile ‘o’opu nopili (Sicyopterus stimulpsoni) – which are about 18 cm high as adults – were discovered with a height of 41 m, it is o’opu’ alamo’o (Lentipes concolor), the two-colored black and orange goby strongest climber. It has been found in ponds on some of Hawaii’s tallest waterfalls, including the more than 300 m high fall of the Hi’ilawe Falls in the northern Waipio Valley of Hāmākua. That’s a long stretch for a fish no taller than five inches. If a human could accomplish the same feat, they would have to scale a surface twice as high as Yosemite’s El Capitanwhile being slapped in the face by boulder-sized balls of water after swimming 4 km longer than a marathon upriver.

Part of climbing efficiently is finding the path of least resistance. For the ‘o’opu, this often means that they cling to the edges of waterfalls rather than the center. This is associated with its own challenges. “The real problem for a fish out of water is not being able to breathe [as long as their gills and skin are wet]”explained Grabowski.” The real danger of running out of water is waste disposal. “It turns out that fish also use their gills to dispose of nitrogen-containing waste. Without the ability to” pee on their gills, “Grabowski said, a fish is really at risk of ammonia toxicity. Although scientists don’t know exactly how , gobies also seem to have adapted to climbing waterfalls to solve this problem.

So the question remains: why go through the trouble?

Here, too, the scientists are not sure. But many who have studied Hawaii’s streams say it could be finding a niche for each species and avoiding competition with one another. In other words: be different and survive.

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Waterfall-climbing gobies are present in perennial streams on all six visitable Hawaiian islands, but Bob Kinzie, retired professor of zoology at the University of Hawaii at Mānoa, Oahu, said, “We have little idea of ​​the actual population density or distribution on any of the islands. “This makes it difficult to determine how populations might change over time.

However, understanding the population fluctuations can be crucial to rescue. Hawaii’s native ecosystem has changed rapidly in the more than 200 years since Europeans stumbled upon its banks. Invasive plants have claimed 60% of the landscape; Wild boars, goats, sheep and cows trample the landscape, eat native plants and cause erosion. and cities today thrive in former valley forests. With the archipelago being one of the most distant inhabited island chains in the world, many creatures have evolved to thrive here and nowhere else, but these specific adaptations often prove detrimental when change is fast.

Because of this, Hawaii has the unfortunate dueling nickname of “Extinction capital of the world” and “endangered species capital of the world‘With good reason: About 75% of all plants and animals extinct to date in the US have occurred in the state, and virtually all endemic wildlife is threatened in some way.

The waterfall climbing gobies are particularly endangered due to their unique brook habitat

The waterfall climbing gobies are particularly endangered because their unique brook habitat – which is also home to two native shrimps and two native mussel species – pervades all the islands’ ecosystems from the coast to the high mountains. Any radical change along its length could alter the current in such a way that it harms the delicate ecosystem of the fish. For centuries, the native Hawaiians understood the fragility of the island’s environment and protected the land in what are known as cake-shaped wedge communities ahupua’a that stretched from the mountain to the sea. Modern church development has not been so kind.

While habitat change and loss continues to be a real and growing threat, it wasn’t the problem with the electricity in the canyon behind the general store, but I didn’t notice it by the time I couldn’t make out an O ‘opu.

The problem was the end point of the creek – instead of gently blending in with the sea, it rained down a cliff in another waterfall. The fish’s unique life cycle begins with an egg that is washed into the ocean downstream by seasonal flooding. Since adolescent ‘o’opu are not born climbers – they swim against the current in streams and spend several days growing and, in some cases, physically transforming before manifesting the ability to climb – this stream wasn’t with the unique Fish life cycle compatible.

Further south along the coast are the paved, ginger and fern lined paths from Akaka Falls State Park lead to its impressive 135 m long namesake cataract and the well-known challenge for waterfall climbing gobies. Its current can be heard well before the waterfall comes into view over a valley, but it would take a telescope to spot a 13 cm fish from here.

The sign on the viewing platform reads “‘o’opu’ alamo’o” – the regional name for the most skillful types of waterfall climbing gobies – and alludes to legendary Polynesian shapeshifters or low (hence the “mo’o” in “alamo’o”). It is a kind of local Loch Ness monster that makes wishes come true: feared and admired, though rarely spotted. The two creatures share a common head shape, it says on the shield, but I see another parallel: although the tiny ‘o’opu can’t Bring floods or change the weather As the mo’o is supposed to do, it is an indicator of the health of the native streams. Like the Mo’o, the climbing fish are the rightful custodians of the islands’ precious freshwater resources.

Perhaps it is best for these unique fish to climb away from human eyes – their mythical feats match their mythical name.

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