Characterization of the Fish Population in the Southwestern Part of the Onega Lake (Karelia) Based on the Results of Long-Term Monitoring

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 4, Pages: 1510-1515

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/1515

Characterization of the Fish Population in the

Southwestern Part of the Onega Lake (Karelia)

Based on the Results of Long-Term Monitoring

Irina Mikhailovna Dzyubuk*

Institute of Biology, Ecology and Agrotechnologies, Petrozavodsk State University, 33 Lenin Ave., Petrozavodsk, 185910, Russia

Received: 28/06/2020

Accepted: 27/09/2020

Published: 20/12/2020

Abstract

The results of the long-term ichthyological studies of the southwestern part (the Sheltozero – Brusno region) of the Onega Lake performed

as part of the environmental monitoring have been presented. This is one of the most productive and clean areas in the lake. The fish

population of the southwestern part of the Onega Lake includes 20 fish species that are representatives of 10 families belonging to six faunistic

complexes. By the number of the species, the Carp family dominates. By the number of the species in this area of the lake, the Arctic

freshwater, the boreal plain, and the boreal foothill complexes are equally important. The species of the freshwater Pontian, the Arctic marine,

and the ancient Late Tertiary complexes together amount to no more than 25 % of the total population. In the southwestern region of the lake,

there are many valuable commercial species (freshwater salmon (Salmo salar Linnaeus, 1758), lavaret (Coregonus lavaretus lavaretus

(

Linnaeus, 1758)), pikeperch (Sander lucioperca (Linnaeus, 1758)), pike (Esox lucius Linnaeus, 1758), etc. Smelt (Osmerus eperlanus

Linnaeus, 1758)) and vendace (Coregonus albula (Linnaeus, 1758)) are the most commercially valuable (75 – 85 %). The population-

ecological analysis has shown a relatively good state of most studied fish species. For maintaining the existing structure and state of the fish

population in the southwestern part of the Onega Lake, a set of measures is required, including the preservation and improvement of the fish

habitat, the conditions for the fish reproduction and feeding; toughening the protective measures during periods with a decrease in the number

of fish species; regulation of fishing, and increasing the amount of fish artificial reproduction, rearing, and releasing into the lake.

Keywords: Fishing, fish population, ecological monitoring, population

Introduction

quality of the lake's aquatic environment, which is deteriorated

due to exerted technogenic, anthropogenic impact. The fish

population is sensitive to any changes of aquatic environment. In

the southwestern part of Onega Lake, i.e. in its cleanest area,

anthropogenic influence manifested itself in the organization and

functioning of the trout cage farm. The author’s studies have

shown that the operation of the cage farm could cause changes in

the state of the aquatic ecosystem and the species composition of

fish in certain areas of the southwestern part of Lake Onega [10-

11]. Therefore, there are urgent tasks of preventing pollution,

eutrophicating the water, optimizing capture fishing, and

developing measures aimed at maintaining the state of the fish

population in the Onega Lake at the optimal level. The study has

been aimed at assessing the ecological and biological state of the

fish population in the southwestern part of the Onega Lake

Currently, the relevance of studying the fish population of

freshwater lakes prone to anthropogenic impact remains high [1-

]. The Onega Lake, the second largest lake in Europe, is valuable

in terms of energy, socio-economic, and environmental

significance for the development of the North-West of Russia.

The fish resources of the Onega Lake have always been and will

remain attractive not only for commercial fishermen and local

fisherfolk but also for tourists. However, the state of this largest

fishery pond largely depends on the way these resources are used.

It is known that irrational, unmonitored fishing decreases the

population and causes the disappearance of valuable commercial

species (sturgeon, salmon, lavaret, etc.). The same consequences

occur when the quality of the aquatic environment changes.

Salmon population in the southwestern part of Onega Lake, the

size of which was catastrophically small due to excessive fishing,

was thoroughly researched. The results of the conducted research

showed that more than 50% of the catches were artificially bred

fish, i.e. one of the most effective ways to preserve the species in

the lake was intensive fish breeding at hatcheries [7-9].

(

Karelia) based on the results of long-term monitoring.

Materials and methods

The object of the study was the fish population of the

Successful existence of fish populations depends on the

Corresponding author: Irina Mikhailovna Dzyubuk, Institute of Biology, Ecology and Agrotechnologies, Petrozavodsk State University,

3 Lenin Ave., Petrozavodsk, 185910, Russia. E-mail: dzyubuk.i.m@mail.ru

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2020, Volume 8, Issue 4, Pages: 1510-1515

southwestern part of the Onega Lake (the Sheltozero – Brusno

region). The fish were caught in 1998 – 2016 from May to

October. The fishing gear was nets (with the mesh of 10 to 70

mm), seine nets (drag nets, tickler chains), and trail nets. A total

of about four thousand specimens of various fish species were

studied.

Onega Lake belongs to the hydrocarbonate class of the calcium

group.

The color of the water is 20 – 25 degrees; it can reach 40 – 50

degrees. The active reaction of the medium is in the range

between 7.0 and 7.8. The content of oxygen is not less than 9.5

mg/l. The content of nutrients is not high (the maximum

concentration of mineral phosphorus is 0.01 mg/l, of ammonia

nitrogen — 0.33 mg/l). The water masses in the southwestern area

of the lake retain an oligotrophic nature [22]. The fish population

of the Onega Lake includes 35 species belonging to 15 families

[21]. The southwestern part of the Onega Lake (the Sheltozero –

Brusno region) is populated by 20 fish species (57 % of the total

number of the species in the lake) (Table 1).

It is known from the local population that sometimes eel

(Anguilla anguilla (Linnaeus, 1758)), chub (Leuciscus cephalus

(Linnaeus, 1758)), rudd (Scardinius erythrophthalmus (Linnaeus,

1758)), and blue bream (Abramis ballerus (Linnaeus, 1758)) are

found in the catches in this area. Some fish species in the

southwestern part of the Onega Lake (the Sheltozero – Brusno

region) are represented by various ecological forms. Of the

lavaret, Coregonus lavaretus widergeni tsholmygensis and

Coregonus lavaretus lavaretus ludoga n. Onegi are met.

Salvelinus lepechini (Gmelin, 1788)) and Salvelinus

lepechiniprofundicola Berg are also found. The large form of

whitefish, European cisco (Coregonus albula kiletz

Michalowsky), is also met.

During the studies, the species composition of the fish in the

catches, the age, sex, size, and weight of the fish were determined.

The Latin name of the fish families and species are given

according to the literature sources widely used in ichthyological

research in Russia [12-14]. The fauna associations were given as

per G. N. Nikolsky [15]. The fish were weighed, measured, their

age was determined, and the fish were opened using the standard

methods [16,17]. The caught fish were measured using a tape

measure and a beam caliper and weighed using an electronic and

a pharmacy weigher, depending on the size of the fish. The age

was determined using an MBS-6 binocular microscope and the

slices of scales, otoliths, and gill covers. To determine the age

of salmonids, whitefish, cyprinids, and other fish species,

scales were sampled; for control, otoliths were sampled

from ruffe and smelt, as well as gill covers –from perch.

When preparing samples, a 10% ammonia solution was used, in

which the recording structures (scales, gill covers) were kept for

0-15 minutes. Then they were placed on glass slides and

examined under a binocular microscope.

All measurements, including weighing, determination of the

age of the fish population, etc., were carried out personally by the

author of the article (one researcher) during multi-year

monitoring, which increases the reliability of the results obtained.

The author personally prepared and examined about 7,000

samples by which the age of the fish was determined. On the basis

of the obtained results of the absolute indicators of the length and

mass of fish, the dynamics of the absolute indicators for a long-

term period, the change in the growth rate, the increments in

length and weight during ontogeny were assessed. Based on the

study of the age composition of fish in the catches, its changes in

the long-term aspect were traced. When the fish were dissected,

the sex of the individuals was determined; on the basis of this, the

sex composition of the fish population and its dynamics were

estimated. The collected data were processed using the standard

methods of analysis of variance [18,19].

By the number of the species, the Carp family dominates (five

species). The Salmonidae and Percidae families include three

species each, the Coregonidae and Gasterosteidae — two species

each, and the Thymallidae, Osmeridae, Esocidae, Lota, and

Cottidae are represented by one species each. The species in the

southwestern part of the lake belong to six faunistic complexes.

By the number of the species, the leading position is taken by the

Arctic freshwater, boreal plain, and boreal foothill complexes

(

25 % each). The freshwater Pontian and arctic marine complexes

account for 10 % each, and the ancient Late Tertiary complex

accounts for 5 % (Fig.1).

Further long-term and systematic studies of the species

composition of fish in Lake Onega will allow assessing the

stability of the state of faunistic complexes and the fish

community of the aquatic ecosystem. The population-ecological

analysis revealed the relatively favorable state of the feeding

school (Shuiskoye) of freshwater salmon (Salmo salar morpha

sebago Girard) in the southwestern part of the lake. In the catches,

the share of commercially reproduced fish reached 53 %. No

significant difference was found between naturally and

commercially reproduced fish in terms of the size and weight,

which were in the range of 33.5 – 88.0 cm and 0.4 – 8.8 kg. The

studies showed a significant reduction in the maximum age of two

ecological forms of lavaret — fera (C. l. ludoga natio onegi) and

pit lavaret (C. l. widegreni natio tscholmugensis) – in catches at

the age of 11+ to 7+ years and 15+ to 9+ years, respectively. The

length of fera (C. l. ludoga natio onegi) in the catches of 1999 had

been up to 55 cm, and its weight was up to 1.5 kg; in 2016, these

indicators in the specimens of the same age did not exceed 40 cm

and 800 g, respectively. For pit lavaret (C. l. widegreni natio

tscholmugensis) the maximum length and weight in this period

had also decreased from 63 cm to 50 cm and from 3.1 kg to 2 kg,

respectively.

Results and discussion

The Onega Lake stretches out from the north-west to the

south-east. The total water area of the lake with islands is 9,943.3

km², without islands — 9,692.6 km². Its maximum length is 290

km; its width is 82 km. The average depth of the lake is 30 m, the

greatest depth is 120 m; the depths of 20 to 40 m prevail. Over 50

rivers and small rivers and about 1,000 streams fall into the Onega

Lake. The major tributaries are the Vodla, Shuja, Suna, and

Andoma Rivers. The largest bays of the Onega Lake are the

Petrozavodsk and the Kondopoga Bays, which have been exposed

to intense anthropogenic effect [20, 21].

The southwestern part of the Onega Lake in the Sheltozero –

Brusno region is one of the purest areas of the water body. All

water masses of the Onega Lake pass through this area; it is

connected with the Ladoga Lake, and through the Neva River —

with the Baltic Sea. The water of the southwestern part of the

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2020, Volume 8, Issue 4, Pages: 1510-1515

Table 1: Fish species in the southwestern part of the Onega Lake

Presence in the southwestern part of the Onega

Family, species

Fem. ACIPENSERIDAE Bonaparte, 1831

Acipenser ruthenus Linnaeus,1758

Сем.ANGUILLIDAE Rafinesque,1810

Anguilla anguilla (Linnaeus, 1758)

Fem.CYPRINIDAE Rafinesque, 1815

Abramis ballerus (Linnaeus, 1758)

Abramis brama (Linnaeus, 1758)

Alburnus alburnus (Linnaeus, 1758)

Blicca bjoerkna (Linnaeus, 1758)

Carassius carassius (Linnaeus, 1758)

Gobio gobio (Linnaeus, 1758)

Leuciscus cephalus (Linnaeus, 1758)

Leuciscus idus (Linnaeus, 1758)

Leuciscus leuciscus (Linnaeus, 1758)

Pelecus cultratus (Linnaeus, 1758)

Phoxinus phoxinus (Linnaeus, 1758)

Rutilus rutilus (Linnaeus, 1758)

Scardinius erythrophthalmus (Linnaeus, 1758)

Fem.BALITORIDAE Swainson,1839

Barbatula barbatula (Linnaeus, 1758)

Fem.COBITIDAE Swainson,1838

Cobitis taenia Linnaeus, 1758

Fem.SILURIDAE Rafinesque, 1813

Silurus glanis Linnaeus, 1758

Fem. ESOCIDAE Rafinesque, 1815

Esox lucius Linnaeus, 1758

Fem.OSMERIDAE Regan, 1913

Osmerus eperlanus (Linnaeus, 1758)

Fem.СOREGONIDAE Bonaparte, 1845

Coregonus albula (Linnaeus, 1758)

Coregonus lavaretus lavaretus (Linnaeus, 1758)

Fem. THYMALLIDAE Gill, 1885

Thymallus thymallus (Linnaeus, 1758)

Fem.SALMONIDAE, Cuver, 1829

Salmo salar Linnaeus, 1758

Salmo salar morpha sebago Girard

Salmo trutta morpha lacustris Linnaeus, 1758

Salvelinus lepechini (Gmelin, 1788)

Fem.LOTIDAE Bonaparte, 1835

Lota lota (Linnaeus, 1758)

Fem.14.GASTEROSTEIDАE Bonaparte, 1831

Gasterosteus aculeatus Linnaeus, 1758

Pungitius pungitius (Linnaeus, 1758)

Fem.COTTIDAE Bonaparte, 1831

Cottus koshewnikowi Gratzianow, 1907

Cottus poecilopus Heckel, 1836

Myoxocephalus quadricornis (Linnaeus, 1758)

Fem.PERCIDAE Rafinesque, 1815

Gymnocephalus cernuus (Linnaeus, 1758)

Perca fluviatilis Linnaeus, 1758

Sander lucioperca (Linnaeus, 1758)

The differences were also significant in the same age groups

of different generations. The increased catching and the focus of

lavaret catching on larger specimens had caused changes in the

age structure of lavaret populations in this area of the lake. It may

be assumed that changes occurred in the feed base of the species,

which affected its size and weight. Currently, the issue of

preserving lavaret in the water bodies in Karelia is very urgent.

This requires continuing the introduction of lavaret (C. l.

Lavaretus (L)) to water bodies, breeding the species at fish farms,

preserving (improving the disturbed) habitat, and reducing the

catching load on this valuable commercial species.

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100,0

80,0

60,0

40,0

20,0

0,0

Onega Lake

south-west part of the Onega lake

Arctic freshwater

Ancient Late Tertiary

Boreal foothill

Boreal plain

Freshwater Pontian

Arctic marine

Figure 1: The ratio of faunistic complexes by fish species in catches in the southwestern part of the Onega Lake

The most important place in the fish resources of the lake is

taken by whitefish (C. albula (L)). Its maximum age in

commercial catches in the Onega Lake is five years; the life

expectancy does not exceed six years. Until the end of the 1980s,

two-year-olds (1+) and three-year-olds (2+) had been of primary

importance in the catches, later, four-year-olds (3+) and five-

year-olds (4+) became of primary importance. This might be the

result of the improved conditions for reproduction and feeding

due to eutrophication of certain areas in the lake and a decrease in

the pressure of predators (mainly salmon (S. salar morpha sebago

Girard) in the southwestern part of the lake) due to their

intensified catching.

The Sheltozero region is one of the main distribution

locations of the large form of vendace - European cisco (C. a.

kiletz Michalowsky). Due to their scarcity, large commercial

catches of this species are rarely observed. The authors managed

to catch and process only 70 European ciscos at the age of 3+ to

of uncontrolled catching. Bream (A. brama (L)) is one of the most

important commercial species in Karelia. In the Onega Lake,

bream has a long life cycle of 29 – 30 years. In the studies of the

authors, no specimens older than 20+ years, longer than 45 cm,

and weighing more than 1,600 g were found. Over many years,

bream age composition and the size and weight parameters were

stable. The study showed a reduction in the age of pikeperch (S.

lucioperca (L)) in the catches at the age of 31+ to 20+ years from

1950 until the present. The population of pikeperch (S. lucioperca

(L)) in the lake is not limited by the feed base since the reserves

of vendace (O. eperlanus (L)) and whitefish (C. albula (L)) are

sufficient. In the past century, pikeperch (S. lucioperca (L)) could

reach the length of 80 cm and the weight of 7 kg; currently, its

size and the weight do not exceed 66 cm and 4,510 g, respectively.

In terms of the age, size, and weight characteristics, the stable

state of roach (R. rutilus (L)), striped perch (P. fluviatilis L.),

Eurasian ruffle (G. cernuus (L)), and other invaluable fish was

noted in this region of the Onega Lake. Vendace (O. eperlanus

(L)) (79 %) and whitefish (C. albula (L)) (7 %) prevailed in the

research catches in the southwestern part of the Onega Lake (the

Sheltozero – Brusno region). Lavaret (C. l. lavaretus (L)) and

eelpout (L. lota (L)) account for a large share in the catches

(7.5 %). Striped perch (P. fluviatilis L), Eurasian ruffle (G.

cernuus (L)), roach (R. rutilus (L)), and other small fish are

quantitatively much inferior to vendace (O. eperlanus (L)) (about

10 %). Pikeperch (S. lucioperca (L)), bream (A. brama (L)), pike

(E. lucius L), and grayling (T. thymallus (L)) are even less

common in the catches (up to 10 %). This region remains a place

for feeding freshwater salmon (S. salar morpha sebago Girard) of

the Shuya school, whose strength is mainly determined by the

amounts of reproduction in the artificial conditions. Single

rainbow trouts (Oncorhynchus mykiss irideus (Walbaum, 1792))

that left the cages as a result of emergencies at trout farms are

found in the catches.

+ years, although the maximum age of European cisco (C. a.

kiletz Michalowsky) is 20 years. The fish aged 5+ to 7+ years

prevailed in the catches. The maximum size and weight of the fish

were 39.7 cm and 570 g, respectively. Vendace (O. eperlanus (L))

is numerous in the southwestern part of the lake, which is also due

to the presence of spawning grounds. It was found that the age

limit of vendace (O. eperlanus (L)) had increased from 8+ (before

995) to 10+ years (after 2003). This was the result of improving

the habitat conditions for the species in this area of the lake. The

size and weight of vendace (O. eperlanus (L)) in the southwestern

part of the lake have been stable over the past decade.

Pike (E. lucius L.) was one of the main objects of commercial

and recreational fishing. In the trawl catches, pike age was 14+

years; its length reached 104 cm, and the weight was more than

0 kg. The age composition, the size, and the weight of pike (E.

lucius L.) in the catches remained stable, which was associated

with a sufficient feed base (a large population of small invaluable

fish). It is believed that as a rule, freshwater predatory fish have a

small population size [23]. However, pike (E. lucius L.) is highly

resilient and can remain highly abundant in the water body in

favorable conditions for living and reproduction with the absence

Conclusions

The development of fisheries in the water bodies of Karelia

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depends in many respects on successful resolving of the tasks of

preserving the fish habitat, optimizing capture fishing, especially

in large water bodies with a significant number of valuable

commercial species, and maintaining the state of the fish

population in the lakes at the optimal level. All this is also

characteristic of the largest fishery reservoir, the Onega Lake,

which is rich in fish resources and has favorable living conditions

for valuable commercial species. As a result of the Onega Lake

monitoring study (1998 to 2016), materials were obtained about

the state of the fish population in one of the most productive and

the cleanest part of the lake, the southwestern one. The fish

population of the southwestern part of the Onega Lake (the

Sheltozero – Brusno region) includes 20 fish species (57 % of the

total number of species in the lake), representatives of 10 families

Authors’ contribution

All authors of this study have a complete contribution for data

collection, data analyses and manuscript writing.

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