Bits & Pieces: Taimen Conservation, Learning to Feed, Walleye Survival

Population Status: High Time for Taimen Conservation

The world’s largest salmonids are the five species of taimen, an imperiled apex predator found in certain waters of Kazakhstan, Russia, Mongolia, and China. The Siberian taimen Hucho taimen of Mongolia is the most common and widely distributed species. Taimen of the Danube River system, often called “huchen” Hucho hucho are apparently the largest, growing to almost 6 feet and over 100 pounds.

Dr. Matthew Sloat of the Wild Salmon Center of Portland, Oregon, recently published a synthesis of what’s known about these remarkable fish.* Two other taimen species are extremely rare. The Sichuan taimen H. bleakeri is still found in low numbers in China’s Yangtze River headwaters and the Korean taimen H. ishikawae is native to the nearly inaccessible border waters of North Korea and China. The fifth species, Sakhalin taimen Parahucho perryi is native to Russia’s Sakhalin Island and Japan’s Hokkaido Island. Recent genetic work has placed them as the sole member of this genus. They’re the only species known to spend part of its life in the ocean, migrating among rivers, brackish waters, and coastal areas.

The scarce research available suggests that all species cover wide territories, with Siberian taimen traveling over 60 miles annually among spawning, feeding, and overwintering areas of river systems. They grow slowly, mature later in life than other salmonids, live longer, and reach larger size, fueled by a piscivorous diet that begins early in life. Their habit of hunting in packs for large preyfish has led to their nickname, “river wolves.” With huge mouths, they may eat fish nearly half their body length, and large Siberian taimen are known to swallow adult chum salmon whole. They also eat ducks, muskrats, and lemmings. Well-traveled fly fishermen use large rodent flies to tempt them. Their size and appetite have spawned many legends among the human inhabitants of these remote and inhospitable habitats.

Sloat notes the irony of their powerful nature and their fragile existence, as their life history makes them highly vulnerable to habitat alterations, population fragmentation, illegal fishing, and climate change leading to warmer waters. All species are on the international Threatened Species list. Conservation efforts are urgently needed, compounded by habitat in some of the most difficult areas for researchers to access. Sloat adds that some protected areas have been established in Japan, Russia, and Mongolia to safeguard habitat, while angling conservation efforts have led to economic incentives for local communities to conserve and protect populations, with limited catch-and-release angling opportunities available through outfitters. It’s hoped that greater awareness of these magnificent fish can spur further efforts to safeguard remaining populations before any extinctions occur.

–Steve Quinn

*Sloat, M. R. 2023. What the taimen said: An urgent call for conservation of the world’s largest salmonids. Fisheries 48:137-140.

From the Archives: Feeding School for Fish

Many anglers assume fish in­stinctively know how to feed effec­tively. But this isn’t necessarily so. Like most animals, fish become more proficient with practice. They alter and adapt tactics and change the timing of feeding movements as they learn to attack and eat unfamiliar prey.

While at the University of Chicago, Dr. Peter Wainwright tested the learning responses of pumpkinseed sunfish as they learned to eat guppies.* The sun­fish were used to eating snails and insects, but had little or no experi­ence eating elusive fish.

Over a six-week training period, pumpkinseeds reduced the aver­age number of strikes required to capture a guppy from 4.0 to 1.7. The fish had to adjust the way they opened and closed their mouths to increase suction and assure that prey were sucked inside. They also changed approach tactics.

When gamefish first encounter unfamiliar prey, they may approach hesitantly, give it a taste test, and then try to eat it. If the prey is strong and elusive, it may escape. A predator may require several en­counters before it takes new prey vigorously and efficiently.

During a study at a Texas reser­voir, divers saw fingerling bass that had fed exclusively on plank­ton and young shad since birth starve to death after the shad dis­appeared.** Small bluegills were nearby, but the bass apparently couldn’t rapidly learn how to at­tack them effectively.

When selecting lures, it often is best to select styles that imitate the shapes and behaviors of prey that the fish you seek have learned to attack and eat. Lures that seem new and different may create curiosity and excitement, but at times draw only tentative nibbles rather than hard strikes. Giving fish multiple encounters with a new lure may up the odds to entice them into striking.

–In-Fisherman

 *Wainwright, P. C. 1986. Motor corre­lates of learning behaviour: feeding on nov­el prey by pumpkinseed sunfish (Lepomis gibbosus). J. Exp. Biol. 126:237-247.

**Manns, R. E. Jr. 1981. Behavior varia­tions associated with ultrasonic tagging and underwater observation of Guadalupe bass in Lake Travis, Texas. M.S. thesis, Southwest Texas State Univ., San Marcos, TX.

Fishery Calculations: Walleyes by the Numbers

It’s a dog-eat-dog world under water, especially if you’re a walleye egg. You need the right water temperature to hatch, plankton blooms to feed on when you emerge from the egg, and plenty of good luck to avoid being eaten by a multitude of predators.  

Nick Baccante was the Senior Research Biologist in the Ontario Ministry of Natural Resources (OMNR) Walleye Research Unit. For six years he studied walleye fecundity—the ability to produce offspring—in a series of study lakes in northwestern Ontario, where they manipulated the walleye population to study the response of the fish to produce eggs.

“In Savanne Lake, production was somewhere around 84 million walleye eggs in total,” Baccante says. “At age-0, which is when they hatch, mortality was about 99 percent. So from 84 million eggs you’re looking at about 10,000 age-0 walleyes. That’s down to 7,000 age-1 walleyes and by the time you get to when they start to mature, at age-5, 6, and 7, you’re down to 2,000 fish.”

What this means if you’re a walleye egg is that you have a 0.0024 percent chance of surviving to maturity. Or, put another way, 99.9976 percent of walleye eggs never make it to adulthood.

–Gord Pyzer

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