The river phase of a young salmon’s life is crucial to the survival of the species.

Heir to the Throne

Martin Silverstone

Jun 29, 2023
An Atlantic salmon parr rests by its home stone. Photo by Jelger Herder.
Gaspé guide David Adams was out on the St. Jean River’s Canoe Pool a few years ago with his guiding partner Allen Morency and two anglers. Before long, they became focussed on three large salmon, which could be clearly seen in the St. Jean’s transparent green waters. Despite numerous fly changes and some excellent presentations, the fish didn’t budge. Perhaps out of frustration, Morency nonchalantly tossed what was left of a mint flavored toothpick into the river.

Almost immediately the water exploded as three or four parr attacked it ferociously, repeatedly nipping at it, even leaping a few feet clear of the water trying to sink it. In a flash, “like lightning” as Adams described it to me, the three big salmon sped over to see what was going on. They hit and pushed the parr away, eventually losing interest and returning to their lies. Adams, Morency and the two anglers watched as the splinter of wood floated downriver while the parr resumed their chase until they faded into the distance. One of the anglers turned to Adams and asked, “Can you tie a toothpick on to my line?”
I guesstimate there must be at least as many parr yarns as “fish that got away” tales. No surprise considering that, although this is not a scientific estimate, Salmo salar are probably most commonly spotted in the form of parr. 
The smallest salmon, parr. A Photo from ASF.
Yet, other than the anecdotes of aggressive parr attacking a fly, or perhaps a toothpick, there isn’t much in the lay literature about these young salmon. At best, they get equal billing with the other phases of salar’s life cycle. Consult any book, magazine article or website and in a description of the Atlantic salmon, a few paragraphs describe how females can lay up to 8,000 eggs, and from these will hatch thousands of alevins soon to be fry. Then maybe one line about the development of the vertical dark bars that define the parr stage and “yada, yada, yada,” as smolt they migrate out to sea.

That’s it for a stage that can live in a river for anywhere from 2 to 6 years in numbers that are surely in the millions. Smolt and adults might get more press due to their spectacular transformation to saltwater creatures and their epic migrations. To make it that far, however, a parr must survive for years in freshwater where death awaits behind every stone, from the sky above and, perhaps the deadliest of all, in the rising frequency of heat waves.

Fortunately, the scientific literature gives more due to this phase of the Atlantic salmon’s life cycle. The aggressiveness that anglers are familiar with has been well studied. Salmon parr are opportunistic, passive feeders which means they prefer to hold their position near a rock or bit of stone cobble and wait for a mayfly, stonefly, or caddis larvae to drift by.

Behavioural studies have shown that they can be true “homebodies”, rarely venturing out from their “home” rock, especially when younger. Dr. Carole-Anne Gillis, before she became the Research Director at Gespe'gewa’gi Institute of Natural Understanding , spent an entire summer observing parr feeding in the Patapedia River. She would mumble codes through her snorkel into a recorder, each referred to different behaviours. When a parr defended its territory, she would scream out “attack-attack,” but through the snorkel the playback came out sounding “aduck-aduck”.
John Burrows captured this parr protecting it's "home stone".
Aggressive parr can nip, bite, or butt an opponent which can cause harm and expend energy. A University of Glasgow PhD candidate, working with parr in tanks, found that these fish could signal their submission through color changes, mostly darkening of the skin and eyes. In this way she hypothesized that differences could be “settled” with less injury or energy expended.
Of course, most parr studies are done when rivers are flowing free of ice. In the past, to find out how many parr survive in winter, researchers were limited to “before and after” scenarios. Although helpful, these did little to reveal details on parr behaviour. Back in 1988 Rick Cunjak, now a scientist who has retired from the University of New Brunswick, began by snorkeling to follow parr in Catamaran Brook, a tributary of the Miramichi. He later used passiveintegrated transponders, also known as PIT tags, to track the par. He found that in winter, tagged fish would leave the security of their “home stone” at night and return during the day.
Mortality was higher in the winter before ice formed, leading Cunjak and his team to believe that the declines in temperature were more physiologically demanding and the parr moved to find better winter shelter. Post ice formation, the environment became more stable and mortality, although still high, was less dramatic.
Parr lead much more complicated lives than a “yada-yada-yada” can describe. Feeding and territoriality are but one aspect of their battle for survival. Sex is another.
A large salmon and parr captured by Nick Hawkins at Mckeens Brook.
Parr become smolt and migrate to distant ocean feeding grounds for the sole purpose of returning to spawn. But for males, this is not the only strategy. It has long been known that parr can become sexually mature and play a role in fertilizing a female’s eggs. These parr literally “sneak” in while the female is depositing her eggs. Some researchers have observed the parr using the cover of adults battling it out to move in.
ASF biologist, Heather Perry, noted in a study for her university thesis, that although the amount of milt produced by a parr is small, there is evidence that it is of higher quality. Also, an interesting fact is that compared to its total size, the parr’s gonads are relatively bigger than those of an adult salmon.
Size is not always the most important factor. The tiny parr, with its smaller packet of milt, can often move undetected under a female, between her and the redd, a close encounter with the eggs perhaps impossible for a much larger adult.

Dr. Tommi Linnansaari, Cunjak’s partner in parr studies, now runs UNB’s Catamaran Brook Research Station where they did the winter parr work. His knowledge of, and concern for, this tiny version of the silver beasts anglers desire is, well, way above par.

“Whenever adult salmon spawn, precocious parr will be present,” he told me. I was surprised as this phenomenon was thought a rare occurrence. But no, he said, and genetic studies have proven that parr may even sire more offspring than adult males.

These days, much of the work at the Catamaran Brook revolves around the impact of thermal events. Like their adult brethren, parr will seek and gather in high numbers when water temperatures rise. Warm water is deadly to salmon at all phases of their life, but by concentrating in cold water plumes, they become vulnerable to other dangers—a lack of food and increased predation. Otter, mink and deadly marauders like mergansers and trout can feast on these conglomerations.

Not to mention careless humans.
Caught in action of active tracking, courtesy of Emily Corey.
The secret, well camouflaged life of parr is their best defense, but this secrecy presents other dangers. Linnansaari told me that he was once observing a cold-water refuge where as many as 15,000 parr had gathered. He saw a group of anglers cross the river in an all-terrain vehicle, something that might have seemed harmless to them. They drove right through the mass of fish, parr scattered everywhere, many thrown into the air. When the researcher hailed down the group to explain they had shattered a critical area and probably killed many fish, the anglers, who had meant no harm, were devastated and apologetic.

A parr’s secret life is a thousand times more complicated than its “public” persona, i.e.: attacking a bomber or an errant toothpick. “It is a life stage that flies under the radar because they are so well camouflaged,” Linnansaari says. “When there is a small green machine at the end of the line, and it hooks a parr, that’s when an angler most often sees one.”

At Catamaran Brook, researchers are lifting that veil of secrecy. One focus is on thermal regulation behaviour, especially how far do parr actually travel to reach cold water refugia. Dr. Emily Corey, found that these usually sedentary fish could migrate up to 8 kilometres to reach the life-saving cool waters. “That’s rather significant, when you think about the size of parr and the conditions in which they make this move,” Linnansaari says. “It would be like me running in the sauna.”

Dreamstime an image by David Hoffmann Photography.
Linnansaari himself has travelled a long way from his birthplace in Finland. Following a degree in fisheries science, he was attracted by an offer to work on the Miramichi, one of the world’s great salmon rivers. Today, the river is not the same as in days of yore, but it worked its magic on the Finn and now, twenty years later, New Brunswick is home. Originally drawn by the allure of the legendary river’s big runs and big salmon, he now finds himself in the thick of the fight to reverse recent trends by studying some of its tiniest residents. In talking with Linnansaari, I could sense a strong attachment to parr that went beyond that of scientist and subject. He appreciates their delicate beauty, the dark bars transected by a line of bright red spots along the lateral line can be almost hypnotic. And when he mentioned seeing hundreds floating dead down the Miramichi River during a bad thermal event, the normally objective scientist’s voice cracked slightly.

To end our discussion on a more positive note, I asked him if he had a favourite parr story. His voice brightened, “What amazes me is their spatial capabilities,” he began. “Take a kilometer of river bottom, with the millions of rocks and cobble. Yet, after leaving their tiny territory, to feed or to avoid a thermal event, they can find their way back to the same post within millimeters.”

He went on to compare this ability as if he was blindfolded in Fredericton and when the blindfold is removed, he would know his exact location by recognizing landmarks and buildings. This kind of homing is well known in birds and even adult salmon, but the fact that these small fish can establish the exact rock from among the millions in a section of river is as wondrous as an adult salmon’s long journey to ocean feeding grounds.

It’s not hard to be awed by such small creatures, so secretive and hidden. They use talents, which remain a mystery to us, to somehow beat the odds and survive and become, as adults, the King of Fish. Thus, any Atlantic salmon parr may be an heir to that, which makes the task of protecting them ever so crucial.

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