Guest Blogger: Michael Vorhis, author of ARCHANGEL suspense thriller, OPEN DISTANCE adventure thriller & more to come

Part 3 presented info on origins and diversity, notoriety, and a few odd points of diet, that we might capitalize on such knowledge. Part 4 discusses some interesting information on coexisting with other species, trout intelligence, a couple of curious fishing trivia points, and hatchery fish.

Sharing the Water

Trout and other species such as grayling or whitefish occupy subtly different habitat niches. Thus they can readily co-exist in the same water. They may both eat common food items, but that does not necessarily mean they are competing with each other across the board. If the water can sustain the combined population, they can share it. Throwing “trash” species up on the bank is neither necessary nor effective. Indeed, species sharing “balanced” water become symbiotic in that their absence would negatively affect the other species.

(By the way, one way to tell whether that rising fish is a trout or a grayling is that grayling tend to blow small bubbles when they rise. Trout do not.)

Trout Brains

We’ve debated whether trout “think” numerous times, but that’s more of an exercise in defining what constitutes “thinking.” But how clever are they, really?

First, to what extent can they apply instinct (a born-in kind of knowledge)? Very well, and very selectively, as they prove to us with annoying regularity.

And then to what extent do they learn, and apply this acquired kind of knowledge by modifying their behavior? Well, its anecdotally provable that they develop a shyness for the same kinds of flies floated past them year after year. On the other hand, there have been Yellowstone cutthroat that have been caught and released on average nearly ten times each. It’s possible that each new hook-up featured a rare and different fly pattern, but more probably trout selectivity depends upon the motivation of the moment. Like with us, if food is scarce, it can be easier to convince oneself that the mouthful in sight is the real meal deal.

Research suggests that brown trout are the more selective, compared to rainbows, cutties, brookies, and many others. That may make them harder to catch, but remember that selectivity is only one measure of intelligence. (If Science used selectivity as the only measure of smarts, my lovely wife would be branded an imbecile.) Rainbows are adaptable, cutthroat have tenacity, goldens are shy…everybody has something.

Trout have a brain about the size of a pea. When you’re skunked for the day, there’s no percentage in dwelling on that fact.

A Few Pieces of Lesser Known Fishing Lore

Probably the earliest account of fly fishing is found in notations of Roman scholar Aelian, circa 200 A.D., who wrote of Macedonians “casting with rods to speckled fish.” We can assume this had been done for many generations already in Macedonia by then.

One old quote lectures, “Give a man a fish and he’ll eat for a day. Teach him to fly fish and he’ll move to New Zealand.”

We hear of “chalk streams,” but what are they? They’re low and slow waterways that precipitate calcium carbonate, causing the streambed to become “cemented” by deposits called “tufa.” This phenomenon causes spawning gravels to form a kind of concrete, which inhibits fish from digging reds. Eggs have a less than ten percent chance of hatching (however those that do produce young that grow quickly and have a better than average survival rate–chalk streams, like other limestone-lined waterways, support abundant life and provide plentiful food). It’s all triggered by increased inputs of nitrogen. Britain sees it; we don’t see it much (if at all) in the USA, in part courtesy of the significant gradients of our mountain flows, which translate to swifter flows.

So many guides emphasize that drift and cast and even choice of flies are of less importance in nymphing than two things: (1) Getting to the right depth in the water column, and (2) setting the hook. The first one we’ve all heard a thousand times, so ‘nuff about that. The second one is a little less dwelt upon, except to repeat that every inkling that the nymph may have bumped across an object down there should be regarded as a take, and the hook should be set. If you feel a bump, set the hook. If you see the line pause or change its angle, in any dimension, in the most trivial way, set the hook Again that has been said enough that it’s nothing new.

But how must a hook be set? First, know that the goal is to move the hook in the fish’s mouth, and that it only need be moved an inch or so…but the move must be abrupt—enough to drive the point home in fish jawbone if necessary. So give it a real good yank, although stop short of breaking your tippet. If there’s no fish there, many times you can simply turn it into an uptake in preparation for another cast. And since a bowed line greatly dampens the rod motion you apply, be sure to factor that in; don’t baby it.

We hear about sweeping the rod tip in the downstream direction on a hook set, to avoid ripping it out of an upstream-facing fish’s mouth. I have to say that this advice may sound credible but it doesn’t hold up to the trigonometric mind. When we yank the rod tip in any direction, the direction the fly will be pulled for the first couple of inches (maybe more) will be the direction the line extends from the hook eye. Because of the drag that water applies to a line, taking up slack instantly (which is what a hook set does) makes the hook start by following the line out along the line’s current path. So if you feel you need to always set the hook downstream, you’re going to somehow need to ensure that the line extends downstream from the fly at all times…and I don’t know how you’d guarantee that. So sweeping the rod tip toward the sea will not guarantee a downstream set. (Myself, I fish in the direction I need to fish, and set the hook with a yank as best I can; if I miss some hook-ups, so be it.)

Hatchery Fish

There are two main schools of thought regarding fish-stocking: Stock to establish a self-sustaining population, and stock so that fishermen can take fish home to the freezer. In the second scenario, stocked fish are often deliberately rendered sterile. Sometimes it is said that this preserves the DNA of the wild fish (while still, of course, making them compete with the stockers for food), and sometimes it is suspected of simply guaranteeing the future of the fish-stocking department, turning citizens hungry for good catches into their salespeople.

Seeking a way to identify hatchery fish from wild-born so that fishing regulations could be designed around put-and-take plantings, hatcheries have long clipped off the tiny “adipose” fin (a small fleshy blob between the dorsal fin and the tail caudal fin) of the fish released into the wild. The idea is that healed-over adipose scars identify a stocker, and that there is no harm done because we knew of no function this vestigial lump performed anyway.

Recently they’ve begun to believe the original “no useful purpose” assumption may have been a bit premature; adipose fins are now proven to be innervated, which clearly points to a sensory function. In particular the adipose fin is now thought by many scientists to be a kind of precaudal flow sensor, and so its removal can be detrimental to swimming efficiency, especially in turbulent water. (The original assumption was perhaps a little heavy on pride in Science and perhaps a little light on humility and respect for the genius and hidden wisdoms of nature; that this small protrusion is up in the line of the flow, immediately before the tail and in a place where no other fin would ever be required, points to a clear sensory purpose and not to an atrophied “fin.” Where do we mount pitot tubes on aircraft, after all? Up top, centerline on the fuselage, directly in the airflow.) Regardless, whether the new understanding will cause a departure from the amputation of the adipose fin or not remains to be seen.

Even if adipose fins are left unmolested, there’s still a good way to tell a farmed fish from a wild fish, especially if the stocker is released after the fingerling stage: Look at the condition of the fins, particularly the tail. Stocked fish tend to suffer from damage to their fins (beat up, ragged, often healed, leaving them kinked or rounded), from having fanned and swiped them against the concrete walls of hatchery tanks. Wild fish usually have fins relatively pristine. (Wild fish can occasionally also suffer from damaged fins and tails, particularly after spawning. But the abrasions are usually of a lesser degree.)

Regarding hybrid fish “designed” for meat harvest, those in farms (and also those hybrids now in the wild) are weaker–less hardy–than their wild natural-DNA counterparts. Thus, stocking can reduce the health of the stream over time. Reproductive potential and ultimately numbers of trout in a river system can be negatively affected by non-sterile stocked fish. This is probably the best argument for sterile stocking programs.

Many strains of “domesticated” (farmed) trout have been in captivity for more than thirty generations.

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Well, that’s about the current size of the knowledge store of “unusual trout facts” I’ve collected this past winter. I’ll keep adding to it, and there’s plenty more out there, but this is a good list. I guess I could add the story of the time I hooked a seven-pound monster rainbow and it evaded my net by leaping far up onto the bank…but it’d only bore you, and besides, the leaping onto the bank part and the seven pounds part would be fibs.

2 Comments

    1. Glad you enjoyed ’em Joe; thanks for wading through them. The last installment was pretty much just a catch-all bin for little things that had no real home in the other three. I did have some fun choosing a valedictorian from the trout “school” though. : )

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