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6THE DYNAMICS OF GROWTH OF THE ZANDER IN THE SMALL ARAL SEA, THE
INFLUENCE OF THE FISHING CATCH OF THE POPULATION RESERVE Kairullaev K.K.1, Barakbayev T.T.2, Iskhakhov G.3, Shudobaeva A.4 Moldakhmetova G.A.5
1Kairullaev Kenes Kayrullaevich - professor, doctor of biological sciences, DEPARTMENT OF "BEEKEEPING, POULTRY FARMING AND FISHING", KAZAKH NATIONAL AGRARIAN RESEARCH
UNIVERSITY, ALMATY;
2Barakbaev Tynysbek Temirkhanovich - candidate of technical sciences, director;
3Iskakov Galym - Researcher, ARAL BRANCH OF FISHING RESEARCH AND PRODUCTION CENTER LLP,
KYZYLORDA;
4Shudabayeva Aitkul - post-graduate student;
Moldakhmetova Gaukhar Abikenovna - Assistant, Master of Agricultural Sciences, DEPARTMENT OF "BEEKEEPING, POULTRY FARMING AND FISHING", KAZAKH NATIONAL AGRARIAN RESEARCH UNIVERSITY, ALMATY;
REPUBLIC OF KAZAKHSTAN
Abstract: this article presents the biological indicators of zander and the long-term dynamics of catch in the Small Aral Sea. According to the results of the study, the age structure of zander, and their size and weight indicators of the species are determined. Fulton fatness indices in zander populations are also defined. The article presents the dynamics of the volume offishing for zander perch in the Small Aral Sea for the period 2006-2019. Key words: zander, ichthyofauna, population, fishing.
UDC: 639.1
Introduction
The Aral Sea is a unique reservoir on the globe. Half a century ago, the area of the sea was 68 thousand km2, its volume was 1093 km3, the average depth was 16.0 m, and the salinity was 10 %o. Until 1960, the water level in the sea and its area were stable, but after the 1960s, the water level steadily decreased, and in 1989-1990 the Aral Sea was divided into two parts. The northern part is the Little Sea, the southern part is the Big Sea. Today, the Little Sea has finally separated from the Big Sea. After the Aral Sea was divided into the Big and Small Seas, their regimes changed in different directions. In the first years, the salinity of the water of the Small Sea began to increase faster than that of the water of the Big Sea. However, since 1988 c 1988 1.5-8.4 km3 of water from the Syr Darya river began to flow into the Small Sea, the increase in salinity of the water of the Small Sea stopped.
Currently, the salinity of the Great Sea is increasing, and thanks to the construction of a dam in the Berg Strait, the hydrological and hydrochemical regime of the Small Sea has begun to improve.
The temporary dam in Berg Strait remained intact for two periods: the first from August 1992 to May 1993 and the second from August 1996 to April 1999. During the construction of the temporary dam, the sea water was desalinated and its area increased. In early April 1999 (before the second dam broke), the water level in the Small Sea in the Baltic system rose to 42.5 m, and its area was 3460 m2. km2. On the southeastern side of the sea, a large brackish area formed, where many insects living in fresh waters began to come. When the dam breaks, the water passing in the freshwater part of the Small Sea will go into the Big Sea. In 2001, the level of the Small Sea reached 39.5 m in the Baltic system, due to which the Butakov and Bolshaya Saryshiga depths were separated from the sea. However, in 2002-2005 the level of the Small Sea reached 40.5 m in the Baltic system due to the outflow of water from the Syrdarya River.
In the early 1960s, the Aral Sea, with its tributaries and firth lakes, was an area where 50,000 tons of fish were caught annually. 80% of the caught fish were very valuable fish - sturgeon, carp, common carp, sole, cake, shemey, zander and whitefish. Misuse of water resources in the Aral Sea basin has caused enormous damage to its fisheries.
The decrease in the level of sea water and the increase in salinity have led to fundamental changes in its ecological system. In 1980, the complete destruction of the industrial ichthyofauna of the sea led to the destruction of its economic significance. At a time when the ecological system of the Aral Sea was in such a stagnant state, the introduction of azau tuyetaban into the sea was a great success.
Only in 1998-2000, on the basis of the international Danish-Kazakhstan project "From Kattegat to the Aral Sea", as a result of assistance provided to the fishermen of the Aral Sea, some progress was made in the development of the stock of crested fish in the Small Aral".
In recent years, international and interstate projects have been developed to improve the environmental situation in the Aral Sea region. The International Bank and the Government of the Republic of Kazakhstan signed an agreement on financing the project "Regulation of the Syr Darya River and Preservation of the Northern Aral" (SARATS).
68 million from the International Bank for the implementation of the SARATS project. 68 million from the bank. US dollars were allocated, including 23 million US dollars for the construction of the Kokaralskaya HPP and 17 million US dollars. US dollars for the construction of the Aklak dam. In 2003, the Russian construction company Zarubezhvodstroy began construction. In 2005, the construction of the Kokaral dam was completed, the river connecting the Small Island with the Big Sea was blocked. After the commissioning of the Kokaral dam in April 2006, the water level in the Small Sea of the Baltic System reached 42.0 m. In recent years (2002-2005), due to the high water content of the Syrdarya River, the water of the Small Sea has become very fresh.
As a result, the area of the brackish water area has increased and the area of distribution of native fish has increased. At present, in the Small Aral there is a commercial stock of the island turtle, carp, flounder, zander and whitefish.
The zander is a large pelagic predator and regulates the abundance of other species in the aquatic ecosystem, which reduces the intensity of competition and stabilizes the community.
When numbers increase, it will eat less efficient, smaller, and less valuable fish. Performs bioreclamation functions in fish farming. The importance of zander as a regulator of the structure of fish habitats in eutrophic water bodies and selective prey is increasing. At the same time, an unnecessary restructuring is created in the fish community, small fish with a short life cycle increase, and valuable species are replaced by less valuable ones.
In the Soviet period, in order to increase the production of fish during biological reclamation, large-scale acclimatization of zander was carried out in many reservoirs. However, in the early 1990s, zander was no longer considered a valuable object of fish farming, and its population was so large that production did not affect its structure.
This is due to a decrease in the growth of fish and the impossibility of storing and transporting the caught zander in an unprepared form. Firstly, in the 2000s, the role of zander as an object of production increased, because due to the high content of fat and protein in zander meat, it was widely used in European countries, and the demand for zander was high.
High export demand for zander has led to the intensification of zander hunting in all reservoirs of Kazakhstan. In most reservoirs, its population began to decline.
Previously, the number of zander in the Aral-Syrdarya reservoir was higher than now, because the interest in the sturgeon population was great. However, due to the decrease in the size of sturgeons, especially in connection with the introduction in 2011 of a special technical moratorium on sturgeon fishing, the role of zander and its interest from a fishing point of view has increased.
To date, the capabilities of the zander as a test target for the detection of multifactorial pollution have not been determined, however, as a predator of the upper trophic level of the ecosystem, the zander is an adequate bioindicator for identifying unfavorable conditions in water bodies.
One of the urgent issues is the conservation of Sunder luciopersa fish stocks in the Small Aral, the constant increase in their stocks, their efficient use and increase in their value for the economy.
Zander perch is one of the professionally valuable fish. The demand for zander fillets on the European market is very high. In particular, the demand from European countries for the fillet of this fish caught from the Small Aral Sea is very high. In this regard, the population of zunder in natural waters is under great pressure. This is due to the fact that with intensive commercial fishing of any species of fish, the possibility of their natural growth and reproduction is reduced and their numbers are reduced. Currently, zunder is sold to Finland, Germany, Hungary and other European countries due to demand and commercial pressure on the natural population. states have started growing in a closed water circulation system (RAS).
Materials and methods
Biological indicators of zunder perch were collected in April-May and August-September 2019 in the Small Aral Sea as part of scientific expedition work together with specialists from BShGEO LLP. During the visit to the Small Aral Sea, ichthyological data were collected from only 12 stations, starting from the tributary of the river. Syr Darya (Fig. 1). The bioassay method consists of the following sequence:
1. place of receipt. Study of a body of water (river, pond, lake, sea, or sea part), places to fish.
2. Date, month, year of receipt, surname, name, patronymic of the assembler and measurer. The name of the fish at the place of residence. The scientific name (Latin) should only be given if the object in question is clearly defined in the fish system.
3.L is the total length or absolute length of the fish. Size from muzzle to longest part of tail wing;
4. l - body length, from the tip of the snout to the base of the caudal wing, i.e., the length of the caudal wing;
5. Weight of fish (g.
or kg). The weight of the fish measures the whole fish without first removing the internal volume (Q - total volume) and the volume without internal volume (q - internal term).
6. Be sure to determine the size of the main fish. If the male type is marked with the female type is marked. A black fish can be clearly distinguished from a fish with its eye closed, then it is written as juv in the evening (inverted juvenalis), which means young.
The purpose of collecting ichthyological samples is to collect data on individual species, sex, age, and other biological indicators of the fish population, their length and weight. Fishing was carried out with standard fishing gear.
The characteristics of standard hunting tools are as follows: each hunting tool is 25 m long and 2-3 m high. mm.
The scientific and technical fishing scheme is a monitoring scheme of 8 fishing months and 24 stations, which makes it possible to obtain information on the species, sex, age and abundance of the fish population.
Fish stock assessment was carried out by direct counting of the number of free fish in the cycle of scientific observation and behavioral analysis in the fishing month. In total, 18 rings with a thickness of 16 to 80 mm, a length of 25 m and a length of 25 m are used for scientific and accurate measurements. Kishnapenko A.I. and Lygapeva E.S. carried out using the method.
The calculation was made as follows:
N = Q^S / C^P, here
N - number or biomass, thousand pieces / ton.
Q is the number of cells or biomass in the data, units.
S is the volume of the reservoir during the zeptei period, ha.
C - the moon, the main volume of the moon used to calculate the professional volume was calculated and determined (length 25 m, height 2 m, the lunar moon of the standard moon is 1.05 ha).
K - the coefficient of the month used is 0.5.
P - the probability of a fish falling on the moon, for carp, sea bass and bream - 0.024, for crucian carp - 0.022, for crucian carp - 0.026.
The calculation that determines the size of the main trade base is presented on the basis of the table, the number of fish stock in the trade size in the base period of fishing.
A biological analysis of 263 zunder trees of different ages caught during the research was carried out. Examinations of all caught fish were made based on common methods [1, 2].
Fig. 1. Survey points in the Small Aral Sea.
Research results
Zander perch is a predatory fish that plays the role of a biological ameliorant of the Small Aral Sea. In connection with the intense salinization of the waters of the Small Aral Sea, the range of zander has expanded somewhat, and it began to be found in all areas of the sea. Studies of recent years have shown that zanders have begun to enter Butakovskaya Bay. Zander reach sexual maturity at the age of three and four years, however, in general, most individuals begin spawning for the first time at the age of five. Migration in the river. The Syr Darya before spawning begins at the end of September. Mass flight is recorded at the end of October and in spring in March-April. Spawning usually begins in the second decade of April at a water temperature of about 7-8 °C, mass spawning occurs in the third decade of April and early May at 14-15 °C [4]. Zunder, like other native freshwater fish, began to live in the Small Aral. In 2001-2003 lived only in the estuarine areas - Shagalalinsky district, in 2004 began to occur in the northeastern and eastern regions, and in 2005 it was recorded in all water areas of the Small Aral, except for Butakov. Bay [5].
Spawning ends in the second half of May at a water temperature of 18-20 °C. During scientific and experimental fishing in the Small Aral in 2020, it was found that the length of the zander is from 15.0 to 58.0, weight from 44 to 2680 g, average body length 27.5 cm, weight 320 g. In 2020, the age composition of zunder included seven generations with a predominance of younger age groups, which indicates the regulation of the intensity of commercial fishing and a steady increase in the population.
As it became known in the course of research in the Small Aral, the age composition of zander trees included 9 generations, and 2- and 3-year-old trees prevailed among them (66.6%).
The limit of mature trees of the zunder population was 9 year old trees. Their average body length was 66.8 cm, and their weight was 4376.5 g. According to Fulton, the average fish density index is 1.3 (Table 1).
As can be seen from the data presented in Table 1 below, 59% of the aspens in the reservoir were 3+ and 4+ year old trees. It can be concluded that when commercial fishing is carried out in accordance with the rules approved in the future (Fishing Rules of the ACM KR dated February 27, 2015), it is possible to maintain the number at the same level. In the course of research, according to local fishermen, adult fish weighing 6-7 kg were found in the fishing gear in the spring months (March-April).
Table 1. The main biological indicators of zander in the Small Aral.
Age Range Length cm Weight, g Fulton density Quanti ty %
(min-max) average (min-max) average
1+ 15,0-18,5 17,3 44-91 69,7 1,3 14 5,3
2+ 18,0-25,0 20,7 75-231 120,7 1,3 82 31,2
3+ 24,0-33,0 28 181-479 296,4 1,3 93 35,4
4+ 31,0-38,0 33,6 365-779 497,7 1,3 54 20,5
5+ 39,0-43,0 40,4 783-1010 919 1,4 7 ,7
6+ 44,0-51,5 46,9 1070-1735 1326,3 1,3 4 15
7+ 54,1-58,1 56,4 2150-2704 2449,6 1,4 3 11
8+ 58,0-62,0 59,5 2505-3650 2878,8 1,3 4 15
9+ 66,0-67,5 66,8 4352-4401 4376,5 1,5 2 08
total 15,0-67,5 41,0 44-4401 1437,2 1,3 263 100
In the research fishery in the Small Aral, the length of the zander was 15.0-67.5 cm, and the weight was 44-4401 g. The average body length was 41.0 cm, the weight was 1437.2 g.
In 2015, the weight indices of this species in the Kapchagai reservoir ranged from 16 to 3170 g [6]. It was noted that the linear and weight growth rate and body density of trees in the population grew at a normal level (Fig. 2).
It shows the sufficiency of fish food in the reservoir for the linear and weight development of zander at each age. This species feeds not only on tender fish in the sea. As we noticed, when studying its internal structure, we found fry of Akmark and its own fry in the stomachs of trees found at point No. 1 (watershed of the Syrdarya river).
The observation of zander cannibalism does not indicate an insufficient food base of the reservoir. Such features are found in the Shardara and Kapchagai reservoirs. No other predatory species were found.
weight, g
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0
200 400 600
length, mm
800
0
Fig. 2. Dynamics of increasing the length-weight of walleye in the Small Aral Sea.
The zunder breeding season is common in the Small Aral, where the water temperature is +12-15C. The main breeding areas are the southern coast of the Small Sea. A similar situation is observed in the Kapchagay reservoir, where zunder do not migrate to the rivers in spring, like other commercial fish, only a small part of the population rises to the Ili River. In early April, productive individuals spawn in the shallow left bank of the reservoir [7, 8]. In
the course of research, the sex structure of the zander was determined, the age structure was determined in 9 generations. According to the sex ratio, female fish predominated in the population. Only among 7-year-old individuals of the male species 67%. Only males were found in 9-year-old zander individuals (Table 2).
Table 2. Age structure of Zander population in the Small Aral sea.
Gender Fish age
1 2 3 4 5 6 7 8 9
female 50 74,1 80,6 75 85,7 75 33 75 -
Male 21,4 25,9 19,4 25 14,3 25 67 25 100
Juvenal 28,6 - - - - - - - -
total 100 100 100 100 100 100 100 100 100
The highest level of zander fishing in the Aral Sea was recorded in 1960-1964 of the last century. In particular, in 1960, 1710 tons of zander were caught, and in 1964 - 9400 tons [3]. Currently, according to the data of the last 14 years in the Small Aral Sea, the lowest figure is 70 tons, and the highest figure is 1025 tons (Fig. 3). In the last 2019, the maximum size of zanderperch catch was 896 tons, and 97.4% was used [5]. In recent years, due to the increased demand for this type of fish, this indicates a large amount of illegal fishing in the sea in excess of the established limit. When poaching, a lot of fishing tools are used, which negatively affects the growth of the population.
2006-2019 period
Fig. 3. Dynamics of zander catch in the Small Aral from 2006 to 2019, tons.
As we have noticed in the course of observations, in some areas of the Small Sea zunder was rarely encountered, probably due to seasonal distribution. However, due to the salinity of the water in the Small Aral, zunder were observed to be evenly distributed throughout the watershed. In addition, its natural conditions are suitable for spawning, however, in order to maintain its population and ensure reproduction, it is important to allow its numbers to be increased through artificial insemination and fishing ponds with zander fry.
Conclusion
Thus, the zander population is evenly distributed in the waters of the Small Aral Sea. In the course of research work, it was discovered when fishing at all points in the reservoir. In the zander population, its age structure was 9 generations. However, in professional fishing there are also higher, that is, adult individuals. The mass of the largest fish specimens in our studies was in the range of 4.3-4.4 kg, and zunder perches weighing up to 9 kg were found in the commercial fishing gear in the sea. In addition, it was noted that the density index is at a normal level. This indicates that its food base in the reservoir is sufficient. The sex structure of the zander population is expected, females make up 68.1% of the total number of fish caught, males - 30.4%, the proportion of immature - 1.5%. There are reasons to believe that the increase in the abundance of this species began in 2005 with the construction of the Kokaral dam in the Small Aral. This is due to the rapid growth of commercial zander fishing, which increased from 70 tons to 1,025 tons between 2006 and 2015. This indicator is directly related to sea level rise and water salinity. However, in recent years, over 2 years (2018-2019), there has been a decrease in catch volumes. One of the reasons for this is illegal fishing, in addition to commercial fishing. This may adversely affect its reserves in the future.
Therefore, at present, artificial breeding of zander perch provides great opportunities for preserving its professional stocks.
Reference
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