Fur-Bearing Trout
The water is frigid as the bank along the Arkansas River in Colorado turns white with snow, its edges blocky, hard with ice. Winter is harsh, solemn, and filled with anticipation. Birds of prey wait in the trees, ready to leap onto mice and rabbits. Elk and deer browse for any bits of vegetation, watchful of hiding hunters. Some try to sleep the season away in warmer, drier caves and burrows, hoping not to be clawed from safety. In the water, though, fear, food, and warmth are not at the forefront of the Fur-Bearing Trout’s mind.
Medium in size, this species of fish is dull brown with a yellow belly and specks of copper, and green; males are more vibrant, showing off hints of reds and oranges too. These fish are special. At the beginning of winter, a handful suddenly change; a sixth soon sport beards and body stubble. Feathery and yellow-brown, the hair spreads and intensifies; interspersed with darker strands, more mottled on top, and light upon the underside, it blends into the gravel bed and surface’s shimmer. As cold weather escalates, the patch envelopes most of the fish. Starting behind the gills, the head is bare, suddenly transitioning to a thick, plumed tuft. The coat covers the body above and below, leaving only fins naked and poking out.
North American scientists were shocked and confused when the animal was first discovered in 1885. Tall tales began circulating of the creatures, to fishermen’s amusement and the public’s delight. A popular origin story, it was said that a few bottles of hair tonic were accidentally spilled onto a clutch of trout eggs in the Arkansas River. As they matured and grew full beards, and heads of hair, fishermen posing as barbers would coax them from lakes and streams with offers of free trims or shaves.
Fantastic and fun, the real mystery remained. Why did this species of fish grow fur? At first, it was believed that the animals developed the coat to stay warm; since the creatures began growing hair in early winter and lost it by summertime, it could not be a coincidence…could it? After a little more research, and a lot of observation, it was determined that this was not the case!
Fish are cold-blooded animals and their internal temperatures depend on the environment. While they can survive in a wide range of temperatures, they still require a level of warmth to survive. Insulating material does not help fish as it does mammals. In seals, blubber helps keep the heat that the animals create inside and the cold out. In fish, which do not generate heat at all, this would mean death. A barrier between them and any potential heat, fur would pose a serious problem.[1]
Another issue with the warmth theory was that not all Fur-Bearing Trout grew hair in the winter. If something is not needed for survival, it more often than not is used for reproduction.
Other fish, like the Brown Trout, have already congregated and checked off their to-do lists; they now settle low in lakes and streams, where the water is warmer. Fur-Bearing Trout still have much to do, saving up their energy for mid-January. Many fish species are divided into egg layers and egg fertilizers; some may spend their life as one kind and transition into the other, like Clownfish or the Asian sheepshead wrasse, but Fur-Bearing Trout transform into something entirely different after spending several years as one or the other. [s]
Sitting between a pair of rocks is a large, stubble-covered fish. The BCWPA has been studying her for the past five winters, watching her swim upstream, lay eggs, and persevere again and again and again. She was named Dory after being caught, tagged, and released - only to be immediately caught two more times by the same net and lure. Entering the next stage of her life, last season was her final year producing young. Now an elder, she will experience more of the world than ever before and possess more responsibilities.
Still, floating low, it is easy to see that the fish feels unwell. Growing and changing is never easy, especially at such a fast pace. All fish, male and female, go through this second maturity once they reach the age of five or six. It begins with an increased appetite in the fall. Fattening up is important; changing requires a lot of energy. As the fish build bulk, their insides display the first physiological updates: new networks of dense blood vessels appear near the gills, fins, brain, and eyes. Called rete, these structures allow the interior of the animal to be at a higher temperature than the water it swims within. Muscles also strengthen, doubling in size. Generated by the fish’s swimming and eye muscles, heat can now be transferred within and throughout the body, but, because of its rete, prevented from coming into contact with cold water flowing over its gills and being wasted. Like the Opah, this anatomical change allows the Fur–Bearing trout to remain active day and night, even in the coldest portions of winter, even in the upper parts of the water. There is a catch, though - they need to keep moving and constantly feed to stay warm and survive. [2]
Near the end of this process, the latter half of the transformation begins. Looking at Dory’s scales, small, round bumps are visible on each. Nearer to the head, more than one bump is present on each, and from others, thick, wispy hair sprouts. The bumps will spread, growing fur in clumps out from each scale. Itchy, fish in this stage often rub against the rocks; they can be spotted in more cragged outcrops and tight spaces once the itch begins. Midway through achieving a full coat, she will also experience a growth spurt; by the end, some of her kind may reach lengths of 70 inches. Though not feeling her best, Dory must seek food several times a day, hunting insects, much smaller fish, and eggs. After her 12-week transformation, she will be stronger and in higher spirits.
January 19. Dory swims upstream, a brown blur in the icy water from above. Sporting a full coat of fur, it is finally time. Her kind has been anxiously waiting, some early to gathering spots. Potamodromous animals (fish that migrate a short distance through freshwater), she and two hundred other Fur-Bearing Trout swim up and downstream, into tributaries and waterways connected to lakes. They look for calm, somewhat shallow waters, places that remind them of where they hatched, and ones that are difficult to access. [s]
Up to twenty fish make it to each meeting spot along the Arkansas River. Not all who show up to this gathering, however, are welcome. Like all species of trout, males are aggressive towards other males. Differentiable by their hooked lower jaws, sharp teeth, and brighter colors, they decide amongst themselves who is allowed to fertilize eggs this year. Amid the ebbing conflict, females lay their two thousand eggs in the open water; after, they may act aggressively toward undesirable males, pushing them away from spawning pools. Some fish are clearly disliked. While the few winning males fertilize eggs, the losers wait on the outskirts; only the largest and strongest are allowed to reproduce. Dory, and other hairy Fur-Bearing Fish, also wait on the sidelines. The dominant males guard the eggs for a few minutes, lashing out even at passing females, before they too start to disperse. The larger fishes’ backs turned, Dory and her compatriots rush towards the exposed egg clutches - but so do spurned rivals. [s]
Called nanny fish, these hairy trout are specialized community members; they guard broods, as well as transport offspring. First, though, their job is to fight off spiteful males. While much older, nanny fish are plenty strong; however, they lack teeth (males losing them in their transformation) and authority. Out of anger, or perhaps the deep sadness of rejection, excluded males cannibalize nests, eating as many young as they can reach. Pushing, battering into, and nipping fins, nanny fish prevent what carnage they can; while no adult fish are mortally wounded, many males will forever exhibit bite mark scars and scraggly fin skin. They cannot linger; time is short. Once females have lain, they return to their wintering grounds, spending the rest of the season moving as little as possible. Males may visit multiple spawning points if they have the energy. Peripheral males often seek second or third breeding pools, where they may be more successful. Yet, if they expend too much energy fighting and traveling or become lost, without adequate resources, or within shallow, cold water for too long, they will perish.
Watchful, Dory floats above a pit of eggs. Satisfied that trouble is gone for now, she puffs up and secretes a substance from her pores; spinning and flowing through the pool, each strand of her fur is coated in a sticky goo, causing the eggs to tangle and adhere to her coat. Three other nanny fish follow suit, swimming in diagonal lines and zigzags, gathering a variety of offspring. Two nanny fish patrol the pool’s only entrance; a resentful, or hungry, male may return. Once a day passes, they will be one less worry. [s] Dory and three other nannies will not remain here until spring, like these guards; the newest, youngest nanny-fish, they set out for a more dangerous excursion.
In each hatchery, one or two nannies watch over developing eggs and chase off predators. The offspring require much: an environmental temperature below 30 degrees Fahrenheit for 60 days, regular access to sunlight, and intermittent turning or movement. Nannies shift eggs higher or lower in their pools to regulate temperatures, move them into sunlight during the day, and flip each egg 3 - 6 times a day. If water conditions pose trouble, such as being too prone to predation, dropping water levels, or too warm, they gather as many eggs in their fur as they can and transport them to more suitable territory. Locations like this, where some Fur-Bearing Trout return each year to breed, are generally low-risk. Dory and other exploring nannies take risks.
A Fur-Bearing Trout hatchery can be wiped out unexpectedly, suddenly. A heat wave. A ravenous, egg-eating creature. A sickly or deceased nanny. While other fish species meet these hurdles with camouflage or defensive qualities, like a bad taste or painful stinger, these fish solve their problem by hedging their bets and being transportable. Half of a spawn’s offspring are kept in traditionally safe hatcheries. The other half is split between younger caretakers. Two or travel north, looking for suitable pools to keep and raise the youths in; any other nannies travel south. Spreading out increases the odds that at least some young will survive. If nannies manage to meticulously tend to their eggs for at least 45 days, their chances of hatching are greatly improved, even if they are unable to provide further care.
Dory swims north, keeping high in the water. As she passes bits of vegetation and easy prey, she feeds. Her partner lags behind, but follows nontheless. Every few hours she pauses, shaking her body to aerate and adjust the eggs; once per break, she flips on her back, allowing the eggs on her belly to feel the sunlight. Though all young require some light, embryos receiving more sun generally produce females. At the end of each day, she secretes another layer of glue to keep the eggs in place; the substance loses its stickyness over time in the water. She will travel up to three weeks searching for a perfect place to settle down.
Since their introduction to North America, fur-bearing trout have spread far and wide. The animals can be found not only in colder portions of the Arkansas River but also in its southern half. Documented in Colorado, Kansas, and, in lesser numbers, Oklahoma, and Arkansas, they have popped up in Canadian waterways, as well as in the Mississippi River. Making their way into the New England area, fur-bearing trout are finding their niche in places like New Hampshire and Maine. Now separated and called the Northern Fur-Bearing Trout, these fish are smaller in size and have grayer scales; while some display the same brown fur as the Arkansas River’s variety, others exhibit new, bright white coats.[s]
Often swimming against the current, it takes several weeks for Dory and her friend to travel a couple hundred miles. Along the way, she stopped to consider two different locations; unfortunately, another nanny already claimed this one. He was unlucky, too, though; only part of his corpse remained. His eggs too long without a caretaker, the location was unsalvageable and obviously too open, easily visited by predators. The second spot the team inspected was better, but too vegetated to navigate; though they needed apt cover, too much caused eggs to get lost or forgotten, and was too hard to move through. Third time’s the charm.
An offshoot of a brook, the gentle, cool waters were perfect: protected by snow-covered grasses, rocks, and branches, not too shallow, and near deeper pools hosting tiny fish and wintering leeches. Here, she has a good chance to make it through the season. Her partner settles in a neighboring section; his spot is just as good, and close enough for both to check in on the other. Allowing each egg to drift off from her fur, she tidies up; the fish tears vegetation and small branches from her way, and pushes gravel up, making tiny, makeshift paths. Eggs are gathered in small clusters around the hatchery, some shaded by the riverbank, the rest more out in the open, but deeper in the water so that their translucent forms remain obscured in the clear water. Some of the offspring she has carried have turned cloudy and yellow; she eats these - they wouldn’t have survived anyway.
For the next 60 - 70 days, she will hunt between tending to the eggs, always on the lookout for dangers: birds, otters, and larger fish. Over time, the pale-yellow center of each egg diminishes, exchanged for growing, developing cells that transform into eyes, a tail, and other organs. If any ceases developing or becomes ill, she culls them from the hatchery, providing more space and attention for healthier eggs.
The warmer it grows, the more the world around will awaken, become more dangerous. If she survives and witnesses the youths hatch into larva, she will have finished her job. Hairy fur-bearing trout lose their coat after 3 months, regardless of their environment’s temperature; they do not grow smaller, however, making them a tasty target for fish-eaters. With their large, warmth-generating muscles, they are prone to overheating in the summer, especially in recent years. Generally, elders cared for three broods in their lifetime; now, they have been reduced to caring for only one, on average, after facing several growing environmental threats.
If she sees spring, Dory will swim freely, hunting and resting as she pleases. The hatchlings do not need to be taught what food they need or how to find and hunt it, nor do they need to be taught fur-bearing fish customs. They are born with all the instincts and knowledge they will ever need, ready to repeat the cycle of life in two years.
Nannies that return for a second or third spawn are most essential to the trout’s reproductive success: they are the ones who call their kind to gather. Releasing their secretions wherever they last raised young, the far-traveling, strong scent brings nearby fish together and tells them: it is time. Without a nanny, the trout become lost, attempting to simply return to the place they were born, often unsuccessfully.
Here at the BCWPA Conservation Center, a few nanny fish are held in its protection for the continuation of the species. Within these tanks also sits several clutches of eggs; BCWPA staff will raise them from fry to parr to adults. Most of these youths will be released into the wild, though some will stay here to produce more young and contribute to further research. Dam-building, increasing temperatures, overfishing, and pollutants are big obstacles we must help these creatures to overcome. Study of the Fur-Bearing Trout have not only brought ecological problems to light, but have also answered many questions, like “Where did these animals come from and why do they have fur?”
A surprise, Fur-bearing trout are actually a non-native species. The only native species of trout in North America are: Gila, Apache, Cutthroat and Rainbowbut trout. However, the fish have existed here for over a century, becoming a part of life here, and are endangered worldwide, stemming from an even more rare fish. One so rare, it is considered a mythological entity.