In the second part about the aquatic inhabitants of the Valdaika River I wish to publish my observations about the predatory fish that live here.
The Valdayka River, which takes its origin in Lake Uzhin.
The most widespread predator is perch Perca flufiatilis. This species lives along the entire riverbed in various biotope zones. Basically, these are small-sized fish that swim in schools near the shore. While the larger ones, from 1 kg weight or more, live in the estuary and in lakes.
Perch Perca flufiatilis in the Valdayka River.
Perca flufiatilis is a curious bold fish not much afraid of humans. The photo below shows the perch posing in front of the camera. Young perch feed on invertebrates, while larger ones – from 2 years old – also hunt for fish. Small but sexually mature perch spawns here in the river, the large ones in lakes. Gelatinous eggs are laid on plants, driftwood and other underwater objects. The spawning occurs in late April – early May, while fry can be seen in the month of May.
Perch Perca flufiatilis posing in front of the camera.
They grow quite quickly reaching by autumn a size of 5-7 cm. It is interesting to watch them at this time. Flocks of several dozen small perches stick around driftwood and large boulders covered with algae.
Juvenile Perca flufiatilis.
Their behavior resembles that of the Tanganyika cichlids of the genus Tropheus and Spathodus. Beginning of October, perches gather in large schools in order to migrate in the deeper areas of the river and into the lakes – on the photo 5 below is a dominant male without stripes – in order to return to their birthplaces in the springtime.
Large school of Perca flufiatilis.
The closest relative of perch, ruff Gymnocephalus cernuus, is also found throughout the channel, but much less frequently. This is for the best, since the ruff is considered a terrible devourer of other fishes’s eggs. The elevated ruff numbers could cause a significant damage to the rest of the ichthyofauna.
Gymnocephalus cernuus, in the Valdayka River.
Ruff prefer a sandy or silty-sandy bottom. His habitat extends from the very shallow areas at the riverbanks to the deepest places. This species feeds on benthic invertebrates but if there is a lack of food it will devour any small fish. Ruffs spawn here, in the river, on the rocky or sandy soils at a depth of 30-60 cm, or on underwater objects, including plant stems.
Esox lucius or pike (photo 7) – the list would be incomplete without this predator! In the river, pike can be observed from late April to late autumn. For the wintertime it moves into the lakes. Pike is found where its food is. In places with many fish there are also many of pikes. The large specimens, reaching up to 10 kg weight, inhabit the mouth of the river. In the river itself they generally weight up to 2-3 kg.
Esox lucius, in the Valdayka River.
By the nature of their diet pikes are ambush predators. Even small ones, hardly reaching 4 cm in length, prey on fry of other fish species. A pike waiting for prey stands motionless somewhere near driftwood or hides in the vegetation.
In a split of a second a victim swimming by ends up grabbed in its mouth. There is no chance to escape. It should be noted that a well-fed predator would never attack any fish.Many times I saw a picture, when a pike was standing near the shore without paying no attention to a small fish swimming in front of its mouth. Large pikes occasionally hunt for frogs, small animals and even waterfowl.
Esox lucius, waiting for a prey.
Pike spawn in the period between end of March and beginning of April, when the ice in the reservoirs begins to melt. This happens during the floods. They perform a group spawning – one large female with several small males. Males rub against the sides of the female, accompanying their caresses with a noisy splash. The mating games are popularly called a pike wedding. The spawning occurs both in lakes and in the river itself in flooded meadows. The fish eggs are laid on the last year’s flooded grass. The fry grow quickly and reach a length of 15-20 cm by the beginning of September. For the winter pikes swim into the lakes, where they continue their active life throughout the cold period.
Lakes in the Valdayka region.
There is one peculiar feature I noticed about pikes. Many times at night in a complete darkness I observed sleeping pikes. But it turns out that they also sleep during the daytime – somewhat from 12 to 14 hours. During the sleep they stand in a daze with no reaction on nothing. If at this time they are approached quietly, then can even be stroked.
Another pike-like predator is the zander Sander lucioperca – here below is a young individual. Unlike pike, zander does not rise up along the river course, but lives in the mouth and in lakes. They are loners. The adult fish live in depths, away from the riverbanks, juveniles near the shore among the vegetation.
Adults feed on fish, actively hunting for it, juveniles – on crustaceans and insects. Occasionally they also hunt for frogs.
The zander spawns near the shore on a sandy ground or under reed roots, where the male builds a nest that looks like a hole of oval shape, 15-20 cm deep and 50 cm in diameter. The male guards the eggs and fry until they grow up and swim away. This species hibernates in the depth of the lakes, but does not stop feeding.
Sander lucioperca, in the Valdayka River.
Another inhabitant of the Valdayka River, who completely crosses out all the stereotypes regarding life in nature, is burbot Lota lota. Burbot was thought to follow the established behaviour of the cold-water fish. It was believed that at a temperature of 10-12°C it becomes lethargic, and at 15°C it stops feeding and hibernates in deep pools. The reality is quite different though.
Lota lota, in the Valdayka River.
Small burbots up to 30-40 cm in size are active in summer at rather high temperatures of 22-25°C. Burbot is more likely to be seen at night while hunting for sleeping fish. At the same time, it moves along the bottom in zigzags and, having stumbled upon a victim – usually a roach or minnow – immediately grabs it.
Hunting Lota lota, in the Valdayka River.
Burbot is famous for its gluttony. Once in a 40cm long burbot I found fifteen of 12cm long chars Barbatula barbatula, which were swallowed during their spawning. In addition to fish, burbot also feeds on large insect larvae, such as dragonflies, for example. Despite the predatory way of life and great appetite, by looking closely the burbot is a pretty fish.
Lota lota is famous for its gluttony.
Burbots prefer to stay over sandy or silty-sandy grounds. They are active all year round, and spawn with the first freeze-up in December-January. Small, but sexually mature individuals remain in the river, joined then for breeding by the large, about a meter long, specimens, which come from the surrounding lakes. The fish spawn on stones in the current. The fry appear after two to three months and begin immediately an active life.
Grayling Thymallus thymallus, a trustful indicator of the water purity, also lives in the Valdayka river. Grayling occurs both in the main channel and in small tributaries, where it may be the mono-species.
Thymallus thymallus, in the Valdayka River.
It stays mostly in a fast current and over sandy-rocky soils near bushes, whose branches hang over the water and next to the riverbank vegetation.
Small affluents of the Valdayka River.
The grayling does not grow large, and turns mature early. In the river, they spawn on rocky shoals, where females build a nest looking like a small pit.
The grayling feeds on aquatic invertebrates and terrestrial insects that have fallen into the water. Sometimes it jumps out by above a meter above the water surface hunting after dragonflies. Individuals of 12-15 cm in size also hunt for fish. Thymallus thymallus lives in small groups and spawns once every three years. The photo below shows young grayling (7 cm) in the company of Alburnoides bipunctatus and Gobio sp., photographed 2 years ago. In my hand I am holding his peer, two years later.
Young grayling with Alburnoides bipunctatus and Gobio sp. in the Valdayka River.
Thymallus thymallus in the Valdayka River.
With a sufficient amount of food grayling does not migrate, staying is in the same habitat. It happened to me to observe the same fish for 6 months on one square meter day and night. For the winter the grayling swims to a deeper places and continues the feeding. It does not tolerate the slightest water pollution. During of 3 years of the road construction along the Valdayka, when the trucks were washed in the upper reaches of the river and water has turned to a terrible mud, the grayling disappeared. After the construction was finished, they did not returned for another two years, until the river was finally naturally cleared.
Predatory fish in the biotope aquarium
Keeping perches and ruffs biotope correct is not a problem. They need a standard rectangular – from 200l – aquarium with sandy-rocky substrate and large stones. Good aeration and bio-filtration should be provided. They can quietly withstand temperatures up to 25-26°C. These species can also be placed together with some cyprinids, belonging to high-bodied species. Perch can swallow narrow-body fish like minnow or bleak even of the size of itself. In this case, the victim’s tail will stick out of the mouth.
It is more difficult to care for pike and zanders. To keep them are more adapted the spacious mono-species tanks.
Grayling is even more difficult to keep in the captivity. This fish is confirmed to fall under strong stress when freshly caught it in the river, so there is little chance of taking it home alive. However, it’s worth a try. It is also better to keep them separately from other fish.
On the photo below there are perches and ruffs in a biotope aquarium.