Special Moment for Sarannoye Lake
24 Aug — 2020
Special Moment for Sarannoye Lake

Lake Sarannoe is located near the eastern coast of Bering island in its northern part. It is surrounded by a ring of hills (Svinye) up to 155 m high. It is the largest freshwater lake on Bering Island, its area is about 31.6 km² . The lake is connected to the ocean by the Sarannaya river flowing from it. It flows into the small Sarannaya Bay of the Bering Sea.

Панорама озера Саранного, о.Беринга. Автор: Ульяна Ледок

Panorama of Lake Sarannoye, Bering Island. Author: Ulyana Ledok

Previously, this lake was called Fedosya Lake. The modern name appeared at the end of the 19th century from the edible grass called saranka , which grows abundantly around the reservoir. The scientific name of this herb is Fritillaria camschatcensis. Native people of North America felt great importance in this plant, as they used it in cooking, in trade relations and in ritual ceremonies.

Most of the salmon are anadromous , that is, they are born in fresh water, go out into the ocean to feed and then return back to spawn. The term anadromous comes from the ancient Greek wordanadromos- "going up", which perfectly reflects the peculiarity of the life cycle of salmon.

What does this very life cycle look like? Here are the adult fis. As a result of the spawning run they laid eggs. In 2-6 months after laying eggs, free embryo is born, to which the remains of the "bag" are still attached - eggs  provide the alevin with nutrients. When the substances in the bag run out, and the fish grow a little, the embryos become young fry and begin to feed on their own with plankton. The fish then enters the parr stage, named in Russian the mottled stage for its striped coloration. They already feed on small invertebrates: insect larvae, zooplankton.

Then, the young salmon must undergo complex changes in the body, designed to ensure that it is able to enter the salt water. This process is called smoltification . Smolts spend part of their life at the mouth of a river while their body chemistry sets up osmoregulation (a set of processes aimed at maintaining a constant osmotic pressure) to escape into salt water. Smolts also acquire a silvery color, which is designed to create visual obstacles for predators in the ocean. Having reached a size of 15-20 cm, smolts go out into the ocean. There they spend up to a year of life, gathering in shoals. Going out in a school into the open ocean, they spend there up to 4 years, accumulating nutrients that will be necessary for them to successfully lay eggs.

Then, the migration back to the native river begins. Most salmon return to the very river system they came from and even to the very stream. This ability is called homing - from the English word home. Scientists are still not sure what allows salmon to determine their location so accurately - there are hypotheses about their orientation in the ocean using the Earth's magnetic field and about finding their native river by the chemical composition of water.

 

Sockeye or red salmon spawning on Bering Island in 2019. Video of the CINBR press service

 When approaching spawning river systems, salmon again undergoes physiological changes - the structure of muscle fibers changes (red muscle fibers used for long-term and stable activities (migration over long distances in the ocean) begin to work less and give way to white muscle fibers, necessary for "explosive" actions, such as a sharp acceleration or jumping, and the biochemistry of the body changes as well. In particular, there is a sharp jump in the development of the gonads - milts in males and eggs in females. Physiological changes also occur. The fish loses its silver tint, the shape of the jaws changes in males, and in some species a characteristic hump grows (especially noticeable in the example of humpback salmon, which got its name precisely because of it). There are interesting hypotheses about the evolutionary development of this hump - perhaps it serves the fish in a peculiar way to determine the optimal depth at which it is safe to spawn (non-drying areas), and perhaps it serves to distract predators from females - the males seem to "sacrifice" themselves, being more simple prey, in order to preserve more important females from the point of view of the population.

Нерка из озера Саранного. Начало нереста 2016. Автор: Анна Малютина

Red salmon from Lake Sarannoye. Beginning of spawning 2016. Author: Anna Malyutina

During the mass run , salmon travel enormous distances, in North America in Idaho, sockeye salmon are forced to travel 1400 kilometers upstream, rising to an altitude of 2100 meters to reach their spawning grounds from the ocean. At Sarannoye, the distances are more modest, but nevertheless the physical capabilities of spawning salmon are amazing.

During the mass run, , many animals are waiting for salmon . Even in the ocean, many predatory fish and marine mammals are eager to feast on them, and on Bering Island they are awaited by seals (harbor seals, which may even enter river estuaries in pursuit of fish), polar foxes, minks, gulls, and crows. Of course, humans also contribute and make life harder for salmon by catching them. These days, nets are such an effective fishing gear that fisheries authorities set special “passing days” when nets are prohibited so that schools of salmon can pass upstream of rivers without interference.

During a mass run, due to various factors, from 3 to 90% of salmon may die  entering the river. There is no way to determine if a salmon approaching a river mouth will be able to successfully make it to the spawning area. The eggs of the female salmon, called caviar, are laid in the recesses dug by her with the help of the tail in the rocky ground. Then, one or several males fertilize the laid eggs, and the female sprinkles it with soil. One female sockeye salmon in Sarannoye can lay up to 3000 eggs.

 Dominant male salmonids protect their fertilized clutches. To do this, they use, among other, their modified jaws - they are especially convenient for grabbing other fish by the base of the caudal fin.

Нерка в брачном наряде (вверху самка и внизу самец). Автор: Анна Малютина

 

Sockeye salmon in breeding color (female above and male below). Author: Anna Malyutina

The state of the salmon organism deteriorates rapidlyafter the start of the mass run. It is programmed evolutionarily. In fact, rapid aging of the body is characterized by the failure of part of the organs and immunosuppression. Therefore, salmon that has completely undergone spawning changes should in no case be eaten raw - a failed liver stops processing harmful substances and they accumulate them in the tissues. Such a breeding strategy, in which exactly one reproductive episode is present before death, is called semelparity (as opposed to iteroparity, as, for example, in humans, which can reproduce several times in a lifetime). Semelparity is also called "big bang" reproduction.

The spawning of salmon fish is a key event for many ecosystems around the world. Salmon carry nutrients from the ocean, which is rich in nitrogen, sulfur, carbon, and phosphorus, into the surrounding biological systems of spawning rivers. Salmon carcasses scattered by animals and the droppings left by them are a rich source of the aforementioned substances in a form available to vegetation. Thus, in the course of a study carried out in Alaska, it was found that at a distance of up to 500 meters from the spawning river, the trees contained nitrogen obtained by them from the decomposed carcasses of salmon and the feces of grizzly bears fishing from the aforementioned river. A 2010 study showed that the density and diversity of some bird species breeding in the estuaries of the rivers of the North Pacific Basin in the fall "directly depended on the biomass of summer spawning salmon." In a 2002 article, scientists compared salmon spawning in terms of level and importance of impact on ecosystems with "the migration of wildebeests to the Serengeti."

 

Average sockeye size:

On Gavanskaya is 1878 grams, 50-53 cm,

on Sarannoye is 1597 grams, 47-50 cm.

Average fecundity of a female sockeye salmon in Gavanskaya in 2020 - 2537 eggs,

Average fecundity of a female sockeye salmon In Sarannoye in 2020 - 2293 eggs,

The reasons for the differences have not been established.

Заповедная Россия English

Заповедная Россия English