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ACCELERATION OF SEXUAL MATURATION OF COMMON CARP BY
ACCELERATION OF GROWTH IN CAGES IN UZBEKISTAN
Zokhidova I.K.
Samarkand State University
https://doi.org/10.5281/zenodo.14027831
Abstract:
In the spring - autumn of 2023, yearlings of common carp were
grown in floating cages in the Tuyabuguz reservoir in Uzbekistan, fed with
balanced high-protein feeds Aller Aqua, which caused rapid growth of carp and
rapid maturation. Already in winter, 2-summerlings of both sexes reached their
first sexual maturation with a standard div length of 41 - 46 cm (in pond fish
hatcheries, carp reaches sexual maturation at the age of 3). Absolute fecundity in
January was 1072.8 - 3008.4 (on average 1773.2) thousand eggs.
Keywords:
carp, Cyprinus carpio, growth, maturation, cages, Uzbekistan
Carp (Cyprinus carpio L.) - a popular pond fish farming object in
Uzbekistan, it is currently one of the few promising objects for intensive
cultivation in cages in local conditions. In open water bodies and in fish ponds,
carp reaches its first sexual maturity at the age of 3-4 years, when it reaches a
standard div length of 32 cm or more (Salikhov et al., 2003, Kamilov,
Kurbanov, 2009). In cages, high-protein feed is used for carp growth. It is known
that the rate of maturation in fish is positively related to fish growth (Kamilov et
al., 2019). In this regard, the goal of this work was chosen - to determine
whether faster carp growth in cages will cause significantly faster maturation in
the conditions of Uzbekistan, which will create new prospects for the formation
of broodstocks of this species in the country. Uzbekistan is located in the
southern zone of the temperate climate with sharp temperature changes
between seasons: hot summer (daytime temperatures from the second half of
May to the end of September remain above 30 ° C) and relatively cold winter
(the average monthly air temperature in January in Tashkent varies from -2 to -
4 ° C). The average daily water temperature warms up above 14 ° C (the
beginning of the growth of warm-water fish) in mid-April, drops below 14 ° C
(the end of the growing season) at the end of October. The period of rapid
growth of carp (the average daily water temperature is above 20-22 ° C) is about
4.5-5 months. (Kamilov et al., 2018). Carp in ponds are grown to a marketable
weight for two years: in the first year up to 20-25 g, in the second year - up to
1000 g or more. The work was carried out at the Fishberg fish farm on the
Tuyabuguz reservoir in the Tashkent region of Uzbekistan in the middle reaches
of the Angren River, a large tributary of the Syr Darya River. In April 2023, one-
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year-old carp (after wintering) from a pond fish hatchery (20-30 g) were
stocked into 4 floating fish cages (each 100 m3). They were fed with balanced
carp feed "Aller Aqua" (for carp) (protein content 33%), the diet was
determined depending on the water temperature and the size of the fish
according to the recommendations of the manufacturer (3% of the total fish
biomass). In January 2024, 40 random carp individuals were examined: the
standard div length, total div weight were measured, sex and maturity stage
were determined visually, gonad weight, absolute fertility of females (Pravdin,
1966).
The dynamics of the average daily water temperature in the Tuyabuguz
reservoir is shown in Figure 1. The level of dissolved oxygen in the water of the
cages was at the level of 5.9 - 6.76 mg/l throughout the growing season, the pH
of the water was 7.3 - 8.8, the total dissolved ammonia nitrogen in the water
fluctuated between 0.00 - 0.01 mg/l. By the end of November, the fish
productivity of the cages reached 43 kg/m3.
Fig. 1. Dynamics of water temperature of the Tuyabuguz reservoir, 2023 y
The sample included females with a standard length of 35–40 (37.9 on
average) cm, with a total div weight of 890–1691 (1323.9) g. There were no
differences in size between the sexes of the carp (the average div weight of
females and males was 1328.5 and 1316.3 g, respectively). The ratio of females
to males in the sample was 1.6: 1. At the same time, the females already had a
noticeable abdomen, which is a secondary characteristic of sexually mature carp.
Note that these are 2-year-old females.
Of the 16 males, only one (39.0 cm and 1447 g) had gonads at stages II–III,
the gonad weight was 16 g, the maturity coefficient was 1.1%. The remaining
males had gonads at maturity stage IV, with a gonad weight of 16-103 (65.5 on
average) g. The maturity coefficient for these males at the end of December was
2.2-7.8 (5.7)%. The overwhelming majority of females (25 out of 26 specimens)
had gonads at maturity stage IV. The females had a total div length of 41-46
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cm, a standard length of 35-40 cm, and a total div weight of 992-1691 g. The
gonad weight at maturity stage IV in January for these females varied within the
range of 67-992 (187.385) g. It was found that larger females had greater gonad
weight, but the strength of the relationship was not high (r = 0.38) (Fig. 2). The
absolute fertility of females in January varied from 1072.8 to 3008.4 (1773.2)
thousand eggs.
Fig. 2. Dependence of the gonad mass of sexually mature two-year-old
females on their div length.
Carp in Uzbekistan is reproduced by stimulating maturation with gonadotropic
substances in females aged 4-5 years (standard length 55-70 cm), which reach
their first sexual maturity at the age of 3 years. It is known that the maturation
rate is positively related to the speed of fish. In cages, as in an intensive system,
balanced high-protein feeds are used, which causes accelerated growth of the
generation. The results we obtained are in good agreement with the literature
(Kamilov et al, 2020), since Uzbekistan is located in the south of the temperate
climate. Here, carp, despite growth cessations for wintering, have fairly rapid
growth and rapid maturation. At the same time, keeping fish in cages provides
new material for this fairly well-studied issue. Thus, in 2023, when cultivating
carp at the Fishberg fish farm in the Tuyabuguz reservoir, where we conducted
experiments, fish farmers fed the fish with balanced high-protein feeds and
achieved rapid growth. At the same time, the cages were stocked with standard
fish seeding material - yearlings from fish hatcheries in the Tashkent region. A
significant part of the fish of the generation grew to a standard length of more
than 32 cm and a total div weight of more than 2.5 - 3 kg. By autumn, these
were two-year-olds. However, already in September, our autopsies showed that
such fish at the age of 2+ (and their share was subjectively more than 60% in the
generation) already had gonads at a well-defined III stage of maturity, i.e. by
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Standard length of females, cm
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spring, at the age of 2 years, they will be sexually mature. This opens up great
prospects for significant optimization of carp reproduction in Uzbekistan for its
increasing reproduction under the conditions of integrated water use.
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