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Article

Age, Growth and Reproduction of Schizothorax pseudaksaiensis of the Turks River

by
Chengxin Wang
1,†,
Na Yao
1,†,
Liwei Xia
1,
Xinyue Wang
1,
Yong Song
1,
Gulden Serekbol
1,
Fangze Zi
1,
Xuyuan Lin
2,
Jin Yan
2 and
Shengao Chen
1,*
1
College of Life Science and Technology, Tarim Research Center of Rare Fishes, Tarim University, Alar 843300, China
2
Xinjiang Production and Construction Corps Agriculture and Rural Bureau, Urumqi 830000, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Water 2023, 15(23), 4044; https://doi.org/10.3390/w15234044
Submission received: 24 October 2023 / Revised: 12 November 2023 / Accepted: 17 November 2023 / Published: 22 November 2023
(This article belongs to the Special Issue Effect of Aquatic Environment on Fish Ecology II)
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Abstract

:
The age, growth, and reproduction of Schizothorax pseudaksaiensis (Herzenstein, 1889), a second-level key protected aquatic species in Xinjiang, were studied using fish ecology methods, and the biological characteristics of its population are discussed. A total of 735 specimens were collected on a seasonal basis from 2021 to 2022 using cages and nets in the Turks River. The fish length ranged from 47.30 mm to 538.60 mm, and the minimum age and maximum age were 1 years old and 23 years old, respectively. The fitting correlations revealed that S. pseudaksaiensis is a uniformly growing fish. The ages at the inflection point for S. pseudaksaiensis were 22.28 (female) and 19.55 (male). The sex ratio was 0.89 (females):1 (males), and the spawning period occurred from April to July. The absolute fecundity was 55,652.01 ± 25,468.78 eggs per individual, and the relative fecundity was 25.92 ± 10.69 eggs per gram. This study provides life history trait data for S. pseudaksaiensis and has theoretical and practical importance for maintaining population dynamics and fishery ecological balance. Additionally, a basis for the protection of fishery germplasm plateau resources is provided.

1. Introduction

Schizothorax pseudaksaiensis (Herzenstein, 1889) is a rare and typical cold-water native fish and one of the main economic fish, with large individuals. According to relevant data, the largest individual was 92 cm long and weighed 5 kg, the quantity of this fish is low, the yield is not high, and it is widely distributed in the waters of the Ili River-Balkhash Lake system, Issyk Lake, and the Chu River [1]. At present, the distribution area has been greatly reduced, and only a small number of S. pseudaksaiensis are concentrated in the Ili River and its main stream [2]. The distribution of S. pseudaksaiensis in Yamadu River is more concentrated, and there is a certain amount of resources, causing it to be one of the main fish caught. However, in the Yamadu River, the number of S. pseudaksaiensis has been decreasing, causing the fish to be difficult to collect [1]. As an ecologically sensitive species of lotus in the aquatic ecosystem of this basin, S. pseudaksaiensis was listed as a second-level key protected aquatic species in Xinjiang in 2019 [3]. Therefore, there is an urgent need to protect and manage S. pseudaksaiensis resources.
Population characteristics are an important basis for fishery resources, among which the age, growth, and reproduction of fish are important indicators [4,5]. At present, descriptions of the geographical distribution and population genetic characteristics of S. pseudaksaiensis are limited [6], systematic studies on its biology and other aspects are scarce, and most studies focus on age identification [7]. Artificial domestication and breeding technology of S. pseudaksaiensis were initially successful only in 2011 [8], and in May 2021, artificial breeding was successfully carried out to supplement population resources through breeding and release. Knowledge of the age structure and growth of S. pseudaksaiensis is restricted to the study conducted by Wang et al. [9] from 2018 to 2020. In their study, the female population ranged from 2 to 16 years, the male population ranged from 1 to 13 years, and the overall growth turning point age was 18.40 years old.
With the intensification of human activities such as fishing and construction of water conservancy projects [10,11,12], the populations of S. pseudaksaiensis have declined and the survival of this species has been greatly threatened. In addition, S. pseudaksaiensis lives in high-altitude and limited areas [2], and due to the unique geographical location and fragile environment, the region is facing serious ecological problems. The population structure of S. pseudaksaiensis is unstable, sexual maturity is late, and the growth rate and fecundity are low. Because of its important characteristic factors [13,14], it is very sensitive to habitat changes. S. pseudaksaiensis distributed in the upper reaches of the Turks River system was selected to study its age, growth, and reproductive characteristics in order to enhance relevant biological data, further understand its population dynamics, maintain the sustainable development of fisheries, and provide a basis for the assessment and protection of fish resources [15].

2. Materials and Methods

2.1. Sample Collection

From 2021 to 2022, 735 S. pseudaksaiensis samples were collected (Table 1) seasonally in the Turks River (Figure 1), one of the largest tributaries of the Ili River. The Turks River originates from the western end of Kharketawu Mountain, the main peak of the Tianshan Khan Tengger Peak (elevation 6995 m) to the north, flowing from west to east through the Zhaosu-Turks Basin near the Kunes breeding sheep farm to join the Kunes River, and then turns west to join the Kashi River into the Ili River [16,17,18].
In this study, which was approved by the Animal Care and Use Committee of Tarim University (approval code: TDD-KYXF 20200426), S. pseudaksaiensis was collected using land cage/hanging nets (2a = 4.00 cm), and land cage/hanging nets were placed 50–60 m apart for about 20 km along the river. Fish were caught from 7 pm to 5 am the next day. The species identification of S. pseudaksaiensis was based on the identification key proposed by Guo et al. [2,19], which was confirmed by experts. After collecting the fish specimens, conventional biological determinations were performed using traditional morphology. To ensure the accuracy of the measurements, 10 traditional morphological data points (accuracy 0.01 mm) were measured point-to-point using a digital display Vernier caliper (CD67-S15PS) (Figure 2), and an electronic balance (LE 403E) was used to weigh the fish (accuracy 0.01 g). After sex identification [20], the otolith was removed and placed in a 0.2 mL centrifuge tube, 4–9 vertebrae and a buttock scale were placed in a 2 mL centrifuge tube, and other tissues were fixed in formalin solution for subsequent treatment.

2.2. Otolith Characteristics

The external side of the lapillus of S. pseudaksaiensis was photographed using a type microscope (SMZ1270 i) and NIS Element software, and the following morphological parameters were measured: OP (otolith perimeter), OA (otolith area), OL (otolith length), OW (otolith width), Rmax (maximum radius), and Rmin (minimum radius). The Shapiro—Wilk test in SPSS 18.0 was used to conduct a normality test for each index of otolith morphology.
Linear equations, logarithmic equations, power equations, and exponential equations were used to fit the relationships between the major morphological indexes of the otolith and the standard length and body weight of S. pseudaksaiensis, according to the Akaike information criterion. The optimal model was selected and the calculation formula is as follows [21]:
AIC = n × ln(RSS/n) + 2k
where n is the number of samples; RSS is the sum of squares of residuals; and k is the number of parameter constants in the equation.

2.3. Age Determination

The otolith was placed side up on the slide, covered with clear nail varnish, air dried, sanded with sandpaper in a circular motion (600#~1000#), and polished with polishing paper. The polishing process of the otolith was observed continuously through a microscope until the central nucleus and otolith increment were clear, and the otolith was dissolved, turned over, and polished until the central nucleus was clear [22] (Figure 3).
The sample was identified under an optical microscope by two or more observers (SMZ-140 N2GG, MOTIC, Xiamen, China), and the age was determined by the number of annual rings on the identification material. If the identification results of the two observers were consistent, the age of the fish was confirmed; if the identification results were inconsistent, the fish was identified again by a third party; if the identification results were inconsistent, the sample was discarded [23].

2.4. Growth Modeling

The growth characteristics were analyzed using the power index relation W = aLb. Analysis of covariance was used to analyze the significance [20]. Student’s t-test was used to examine the correlation between the b value and 3 and to judge whether S. pseudaksaiensis grew at a uniform rate. Fulton’s condition index was calculated by the formula K = W/L3 × 100,000, and its growth characteristics, fish abundance, nutritional status, etc., were observed [24,25].
The von Bertalanffy growth equations were fitted [20,24]:
L t = L ∞ ( 1 - e - k ( t - t 0 ) ) W t = W ∞ ( 1 - e - k ( t - t 0 ) ) b
where Lt is the standard length at age t; Wt is the body weight at age t; L∞ is the progressive standard length; W∞ is the progressive body weight; t0 is the age at which the standard length and body weight are equal to zero in the theoretical state; k is the average curvature of the growth curve; and b is the allometric growth index.
The apparent growth value and inflection point age were calculated by the growth rate and growth acceleration [20,24]:
d L / d t = L ∞ k e - k ( t - t 0 ) d W / d t = b W ∞ k e - k ( t - t 0 ) [ 1 − e - k ( t - t 0 ) ] b − 1 d 2 L / d t 2 = − L ∞ k 2 e - k ( t - t 0 ) d 2 W / d t 2 = b W ∞ k 2 e - k ( t - t 0 ) [ 1 − e − k ( t − t 0 ) ] b − 2 [ b e − k ( t − t 0 ) − 1 ]
where dL/dt is the standard length growth rate; dW/dt is the body weight growth rate; d2L/dt2 is the standard length growth acceleration; and d2W/dt2 is the body weight growth acceleration.

2.5. Reproductive Characteristics

After the fresh samples were dissected, the gonads were observed to determine sex and maturity. According to the criteria of gonad development stages [20,26], the developmental stages of gonads were judged first, and the results were expressed as I~VI. The fresh gonad samples were fixed in Bouin’s solution, transferred to 70% ethanol solution 48 h later, and brought to the laboratory for dehydration with 75%, 85%, and 95% anhydrous antimony degree ethanol and gradient xylene transparency. Then, the soaked gonad tissues were embedded (sections 5–7 μm thick were obtained with a paraffin microslicer) and observed and photographed under a microscope after HE staining [26,27].
According to the gonadal tissue section method used to observe whether gonadal development reached stages IV to V, the monthly change in gonadal development and the gonadal maturity coefficient (GSI) were used to judge the reproductive season [20,28]. The calculation formula is:
GSI = 100 (WG/W)
where WG is the gonadal weight, and W is the body weight.
The ovaries with basically mature eggs (stage IV) were collected, approximately 100 eggs were randomly selected from each tail sample, the eggs were photographed under a microscope (SMZ1270 i), and the egg diameter was measured using NIS Element software. Gonadal histological observation, gonadal maturity coefficient (GSI), and egg diameter distribution were used to determine the spawning type. The whole ovaries of 50 female fish in stage IV were weighed, approximately 5.0 g was removed from the anterior, middle, and posterior parts of the ovaries and fixed with 10% formalin solution, and all eggs were counted. Absolute fecundity (F) and relative fecundity (RF) were calculated from the eggs in the counting part.

3. Results

3.1. Size and Age Structure

Using the otolith as the age identification material, 735 S. pseudaksaiensis were aged from 1 to 23 years, and the most common age was 7 years (Table 2). There were 346 females and 389 males of S. pseudaksaiensis, among which the standard body length of the females was 260.83 ± 113.90 mm (49.04–538.60 mm) and the standard body length of the males was 207.53 ± 85.55 mm (47.30–458.39 mm) (Figure 4). The body weight of females was 465.85 ± 571.15 g (2.03–2850.00 g), and the body weight of males was 203.61 ± 212.65 g (1.59–1600.00 g) (Figure 5). There was no significant difference (p > 0.05) between male and female standard length/body weight.

3.2. Fish Growth

3.2.1. Length–Weight Relationship

The correlations between the standard length and body weight of the S. pseudaksaiensis population and the female and male populations were fitted as follows (Figure 6):
Total: W = 8.48 × 10−6L3.1095 (R2 = 0.9749, n = 735)
Female: W = 1.28 × 10−5L3.0436 (R2 = 0.9756, n = 346)
Male: W = 1.73 × 10−5L2.9759 (R2 = 0.9650, n = 389)

3.2.2. Fulton’s Condition Index

The index of the S. pseudaksaiensis population was significantly higher at ages 1–5 and 11–15 (Figure 7). There was no significant difference between the different age groups (p > 0.05). The mean index of S. pseudaksaiensis was 1.5344 in general, with 1.5291 for males and 1.5104 for females. There were more male fish than female fish in total.

3.2.3. Otolith Morphology

The lapillus otolith of S. pseudaksaiensis was large, generally square in different shapes, thicker in the center, and thinning toward the outer edge, with distinct protrusions in the center of the outer side. The back of the otolith was wavy, and there was an obvious depression in the center. The abdominal margin was a shallow arc, the basal lobe was not developed, and the main intersulcus was not obvious.
A paired sample t-test showed that there was no significant difference between the left and right otolith morphology of S. pseudaksaiensis (p > 0.05), so the left otolith was used uniformly.
The otolith area was 1.82 ± 1.28 mm2 (0.42–6.86 mm2), the otolith minimum radius was 1.32 ± 0.27 mm (0.62–2.35 mm), the otolith maximum radius was 1.93 ± 0.45 mm (0.83–3.92 mm), the otolith perimeter was 5.45 ± 1.25 mm (2.42–10.69 mm), the otolith length was 0.95 ± 0.07 mm (0.41–1.85 mm), and the otolith width was 0.68 ± 0.12 mm (0.31–1.20 mm).

3.2.4. Relationship between the Morphology of Otoliths and Standard Length/Weight

The relationships between the otolith morphological indexes and the standard length and body weight of S. pseudaksaiensis were fitted and analyzed using four mathematical models: linear, exponential, logarithmic, and power functions. The model with the lowest AIC value was selected as the optimal model. The best fitting model was the power function (Table 3 and Table 4 and Figure 8 and Figure 9). After correlation analysis, it was found that the R2 values were all greater than 0.78 and the average was higher than 0.81, showing a high correlation, and there was no significant difference in the fitting effect (p > 0.05). The correlations between body weight and otolith morphological indexes were higher for S. pseudaksaiensis than for standard length.

3.2.5. Growth Equation

The growth equations of the female and male populations of S. pseudaksaiensis were fitted, and the growth rate and growth acceleration equations were obtained by first and second differentiation, respectively (Table 5). The fitting results of the growth model are as follows in Figure 10 and Figure 11.

3.3. Reproductive Biology

The female to male ratio of 735 S. pseudaksaiensis samples was statistically analyzed, and the male to female ratio was 0.89:1. According to the characteristic section of gonad tissue of S. pseudaksaiensis (Figure 12 and Figure 13), the gonad maturity coefficient (GSI) (Figure 14), egg diameter distribution (Figure 15), and the proportion of stage IV to V gonad cells, the GSI and number of eggs increased gradually from February, peaked in June, and then gradually decreased until September. Phase V gonads were most abundant in June, followed by May and July, and there were more mature cells in the gonad sections from June, suggesting that S. pseudaksaiensis had a peak reproductive period from May to June.
The egg diameters of stage IV gonad eggs in 8 months of samples from March to June 2021 and from July to October 2022 were measured. The egg diameter distribution diagram (Figure 15) showed that the egg diameter distribution of S. pseudaksaiensis was unimodal, with an average egg diameter of 2.19 ± 0.26 mm. The mean egg diameter was smallest in October (mean egg diameter 1.80 ± 0.34 mm) and largest in June (mean egg diameter 2.49 ± 0.18 mm). The distribution of egg diameters in all months showed a single peak, which suggested that S. pseudaksaiensis is the synchronous spawning type. The number of eggs from female fish in stages IV to V was counted. The standard length was 499.44 ± 40.06 mm, ranging from 440.84 to 594.71 mm, and the body weight was 2229.06 ± 680.86 g, ranging from 1503.00 to 4200.00 g. The absolute fecundity was 55652.01 ± 25,468.78 grains/tail, ranging from 14,500.00 to 112,636.26 grains/tail. The relative fecundity was 25.92 ± 10.69 grains/g and ranged from 3.71 to 47.63 grains/g.
By selecting the model with the lowest AIC value as the optimal model, the results showed that there were linear relationships between fecundity and the body length and body weight of S. pseudaksaiensis (Table 6 and Figure 16). The fitting equations are as follows:
F = 624.14 L − 256868.74 (R2 = 0.9615)
F = 35.80 W − 24149.19 (R2 = 0.9113)

4. Discussion

This is the first time the age, growth, and reproduction of S. pseudaksaiensis in the Ili River system have been studied. Our results showed that S. pseudaksaiensis prefers to live in high-altitude cold water, its uniform growth pattern is closely related to aquatic organisms in the Ili River, and it is a slow-growing fish with a long life span. The formation of its reproductive characteristics reflects its adaptability to the habitat environment. Therefore, to enhance and sustain the reproduction and survival of S. pseudaksaiensis, strengthening water environment management and the multiplication and discharge of the Ili River is necessary.
The water replenishment sources of the Turks River are mostly glaciers and mountain snow. The altitude of the river basin is high (800–4600 m), the water temperature is low, there are many tributaries and abundant water energy resources. Water physical and chemical indexes such as water temperature, pH, conductivity, dissolved oxygen, major ions (Na+, K+, Cl−), and water chemical types are suitable for plateau fish survival [1,29,30]. In fish maturation, size, age, and growth are closely related to water temperature and food supply. Borwn et al. [31] found that in W = aLb, the power exponent b is used to judge fish growth. The total b value was 3.1095, with 3.0436 for females and 2.9759 for males, so it was determined to be an isometrically growing fish. In the Turks River, the seasonal variation in phytoplankton was obvious and consistent, and diatom biomass dominated in all seasons; the seasonal variation in zooplankton was not obvious, and spring rotifer biomass was dominant [1]. There are many organic debris types and benthic species in Turks River water, especially hookshrimp and Chironomidae [1,2], which provide effective food sources for indigenous fish and cause the growth trend of S. pseudaksaiensis to be stable and uniform. In this study, S. pseudaksaiensis preferred to live in cold water at high altitudes, and its adaptability varied with water temperature, resulting in slow growth, which was closely related to aquatic organisms in the Turks River, etc. These factors may be the major reasons for its uniform growth. The overall plumpness coefficient of S. pseudaksaiensis in the female group was slightly higher than in the male group. The plumpness of female fish was higher than that of male fish at 1–5 years of age, and the growth of female fish was faster than that of male fish before sexual maturity. The plumpness of female fish decreased at 6–10 years of age, increased again at 11–15 years of age, and then dropped to a stable level. This change may be closely related to sexual maturity age, reproductive energy consumption, water temperature, and food levels [1,7,32].
In fish age identification, the otolith radius is often used to infer the fish age change, with some researchers believing that otolith size and fish growth are controlled by the same metabolic process [33], and its strong correlation can be reflected by R2. Some scholars found that the R2 values of 16 Mediterranean deep-sea fish and European bass (Perca fluviatilis) were all greater than 0.8 [34,35]. In this study, the correlation of S. pseudaksaiensis was high (R2 > 0.8). Although the otolith had been growing, the growth on different axes was not uniform. Renones et al. [36] believe that with increasing fish age, the continuous deposition of otoliths to the distal surface results in unequal growth of otoliths and fish standard length. Therefore, for older fish or slow-growing fish, the accuracy of using otoliths to calculate the length of the fish body is not high.
During fish ontogeny, reproductive parameters are fitted with information from the animal phenotypic index measured in different growth periods using mathematical models [37], and their changes follow different strategies [38]. The female population of S. pseudaksaiensis showed L∞ = 737.7, W∞ = 6853.3, k = 0.05, t0 = −0.59, and ti = 22.28; and the male population showed L∞ = 667.0, W∞ = 4447.2, k = 0.05, t0 = −0.36, and ti = 19.55. At the turning point age, the male population was obviously smaller than the female population. Compared with S. oconnori [24] and S. waltoni [39], the ti of S. pseudaksaiensis in this study was higher, which was related to the difference in habitat, such as the habitat altitude of the fish species [40]. The growth coefficient k is a key parameter in the assessment of fish stock potential [41,42,43], and fish with a value of k between 0.05 and 0.10 are slow-growing fish. S. pseudaksaiensis had a low k value (0.05) and a high asymptotic standard length (L∞), indicating that it is a fish with slow growth and a long life. Comparing this with the previous study on S. pseudaksaiensis growth, it was found that the L∞ obtained in this study was 654.80 mm higher than that in the previous study, and the growth coefficient k (total 0.05, female group 0.05, male group 0.05) was lower than that in the previous study on S. pseudaksaiensis (total 0.06). The reasons may lie in the different distribution of standard length or the different composition of age.
Reproductive characteristics are not affected by only internal factors such as genetics but are also closely related to external factors such as the habitat water environment and nutrition, including spawning type and fish fecundity [44,45]. The sex ratio is usually related to the reproductive habits of fish, and a change in the sex ratio is always conducive to the maintenance of a certain population [46]. Having more females than males helps to increase the population [20]. The gonad index (GSI) reflects the variation in gonad development and the proportion of fish energy distribution [47,48]. The fecundity of fish reflects its investment in reproduction and its reproductive strategy [49,50]. The male/female ratio of the S. pseudaksaiensis population in this study was 0.89:1, which was not significantly different from the theoretical ratio (1:1) (p > 0.05), but the male population was larger than the female population, indicating that males were dominant in this reproductive population, which was similar to the S. yunnanensis [51] population. The gonadal index of S. pseudaksaiensis reached its peak in June, the egg diameter in June was close to the maximum, and the egg diameter distribution was “unimodal,” indicating that S. pseudaksaiensis belongs to the synchronous spawning type, breeds once a year, and the breeding period is short, concentrated in May to July. During this period, the Turks River has optimal external conditions (high water temperature, sufficient light, etc.), which are conducive to the development and normal growth of embryos and larvae [52]. However, S. pseudaksaiensis lays its eggs on the bottom, on gravel and other substrates during the breeding period, and the eggs sink [20]. Therefore, the biggest potential danger is hypoxia, as the eggs may be covered by silt and infected by microorganisms, etc. However, Schizothorax eggs are toxic and rarely eaten by predators [53]. Many Schizothoracinae species have the same spawning type as S. pseudaksaiensis, such as S. waltoni [39], S. oconnori [24], and Oxygymnocypris stewartii [54]. The fecundity of the S. pseudaksaiensis population was significantly higher than that of other Schizothoracinae species [24,39,54], and the relationships between absolute fecundity and the standard length and body weight were consistent with the results of studies on Oxygymnocypris stewartii [54]. The relationship between fecundity and body length of S. pseudaksaiensis was linear, which was similar to that of Oxygymnocypris stewartii and S. oonnori. The differences in nutrient intake and energy distribution of fish living in the plateau water environment with scarce food resources may lead to differences in their fertility. Therefore, comparative studies on fertility should be conducted on the basis of eliminating the effects of individual fish or weight [55].
Growth and reproduction constitute the processes of population growth and replenishment. The growth of fish tends to ensure that the species has the longest time to reproduce, and reproduction is linked to other life events to ensure reproduction of the population [20]. The growth of fish is divided into three stages: the rapid growth stage before sexual maturity, the stable growth stage after sexual maturity, and the growth aging stage [56]. The larger inflection point age of S. pseudaksaiensis indicates that the sexual maturity is older, growth is rapid before sexual maturity, and material and energy accumulation can ensure high fertility and maintain the population number. This study will be essential for the protection and reproduction of S. pseudaksaiensis resources in natural waters and their artificial reproduction.

5. Conclusions

Due to the particularities of the water environment, such as high habitat altitude, low habitat temperature, and food abundance, the number of S. pseudaksaiensis is not very large in the wild, showing certain evolutionary adaptation characteristics and possessing high scientific research, development, and utilization value. The protection of S. pseudaksaiensis should be strengthened in the future. The biodiversity protection of the Ili River Basin should also be strengthened to provide a scientific basis for the protection of plateau fish germplasm resources.

Author Contributions

Conceptualization, C.W. and N.Y.; Software, C.W. and L.X.; Validation, X.W. and Y.S.; Investigation, G.S. and F.Z.; Data curation, X.L. and J.Y.; Writing—original draft preparation, C.W. and N.Y.; Writing—review and editing, S.C. All authors have read and agreed to the published version of the manuscript.

Funding

The Special Financial Project of Ministry of Agriculture and Rural Affairs (Fishery Resources and Environment Survey in Key Waters of Northwest China); the Corps Science and Technology Bureau Key Areas of Science and Technology Public Relations Plan (2022DB019); and the Key Laboratory Project of Tarim Animal Science and Technology Corps (HS201902).

Institutional Review Board Statement

All experimental protocols were approved by the Ethics Committees of Tarim University of Technology (approval code: TDD-KYXF 20200426, approval date: 26 April 2020) and adhered to animal welfare laws, guidelines and policies.

Data Availability Statement

Because the project is not finalized, a link to the data has not been made public.

Acknowledgments

Thank you to our Fisheries Department colleagues and Yingcheng Studio.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The sampling area of S. pseudaksaiensis in the Turks River.
Figure 1. The sampling area of S. pseudaksaiensis in the Turks River.
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Figure 2. Morphological measurement of S. pseudaksaiensis. Note: 1. Total length; 2. Standard length; 3. Body depth; 4. Head length; 5. Snout length; 6. Eye diameter; 7. Length of caudal peduncle; 8. Depth of caudal peduncle.
Figure 2. Morphological measurement of S. pseudaksaiensis. Note: 1. Total length; 2. Standard length; 3. Body depth; 4. Head length; 5. Snout length; 6. Eye diameter; 7. Length of caudal peduncle; 8. Depth of caudal peduncle.
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Figure 3. Age identification material of S. pseudaksaiensis (6+) (circles represent annuli).
Figure 3. Age identification material of S. pseudaksaiensis (6+) (circles represent annuli).
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Figure 4. Standard length distribution of S. pseudaksaiensis.
Figure 4. Standard length distribution of S. pseudaksaiensis.
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Figure 5. Body weight distribution of S. pseudaksaiensis.
Figure 5. Body weight distribution of S. pseudaksaiensis.
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Figure 6. Length–weight relationship of S. pseudaksaiensis.
Figure 6. Length–weight relationship of S. pseudaksaiensis.
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Figure 7. Fulton’s condition factor of S. pseudaksaiensis among different age groups.
Figure 7. Fulton’s condition factor of S. pseudaksaiensis among different age groups.
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Figure 8. Relationship between otolith morphological index and standard length of S. pseudaksaiensis.
Figure 8. Relationship between otolith morphological index and standard length of S. pseudaksaiensis.
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Figure 9. Relationship between otolith morphological index and body weight of S. pseudaksaiensis.
Figure 9. Relationship between otolith morphological index and body weight of S. pseudaksaiensis.
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Figure 10. Growth model of the female population of S. pseudaksaiensis.
Figure 10. Growth model of the female population of S. pseudaksaiensis.
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Figure 11. Growth model of the male population of S. pseudaksaiensis.
Figure 11. Growth model of the male population of S. pseudaksaiensis.
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Figure 12. Ovarian development in S. pseudaksaiensis. Note: (a), Ovary at stage Ⅱ (50 μm); (b), Ovary at stage Ⅲ (100 μm); (c), Ovary at stage Ⅳ (100 μm); (d), Ovary at stage Ⅴ (50 μm); O2, Perinucleolar oocyte; O3, Cortical alveoli oocyte; O4, primary yolk oocyte; O5, Second yolk oocyte; O6, Tertiary yolk oocyte.
Figure 12. Ovarian development in S. pseudaksaiensis. Note: (a), Ovary at stage Ⅱ (50 μm); (b), Ovary at stage Ⅲ (100 μm); (c), Ovary at stage Ⅳ (100 μm); (d), Ovary at stage Ⅴ (50 μm); O2, Perinucleolar oocyte; O3, Cortical alveoli oocyte; O4, primary yolk oocyte; O5, Second yolk oocyte; O6, Tertiary yolk oocyte.
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Figure 13. Testis development in S. pseudaksaiensis. Note: (a), Testis at stage I (100 μm); (b), Testis at stage II (100 μm); (c), Testis at stage Ⅲ (50 μm); (d), Testis at stage IV (100 μm); (e), Testis at stage V (100 μm); (f), Testis at stage VI (50 μm); sg, spermatogonia; sc, spermatocytes; st, spermatids; sz, spermatozoa.
Figure 13. Testis development in S. pseudaksaiensis. Note: (a), Testis at stage I (100 μm); (b), Testis at stage II (100 μm); (c), Testis at stage Ⅲ (50 μm); (d), Testis at stage IV (100 μm); (e), Testis at stage V (100 μm); (f), Testis at stage VI (50 μm); sg, spermatogonia; sc, spermatocytes; st, spermatids; sz, spermatozoa.
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Figure 14. GSI in different months of S. pseudaksaiensis.
Figure 14. GSI in different months of S. pseudaksaiensis.
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Figure 15. Monthly size frequency of oocytes for S. pseudaksaiensis.
Figure 15. Monthly size frequency of oocytes for S. pseudaksaiensis.
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Figure 16. The relationship between absolute fecundity and standard length/body weight of S. pseudaksaiensis.
Figure 16. The relationship between absolute fecundity and standard length/body weight of S. pseudaksaiensis.
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Table 1. Information on S. pseudaksaiensis samples.
Table 1. Information on S. pseudaksaiensis samples.
TimeSiteNumberStandard Length/mmBody Weight/g
RangeMean ± S.D.RangeMean ± S.D.
Apr. 2021 (Spring)E 80°57′, N 42°57′—E 80°96′, N 42°95′19248.41~534.84244.01 ± 94.041.59~2500.00344.31 ± 452.61
Jun. 2021 (Summer)19647.30~532.60187.04 ± 112.131.83~2600.00228.12 ± 412.48
Oct. 2021 (Autumn)17369.82~538.60256.20 ± 110.455.00~2850.00422.50 ± 515.65
Jan. 2022 (Winter)17476.05~515.01247.96 ± 77.078.84~2450.00324.59 ± 349.15
Table 2. Age structure composition of S. pseudaksaiensis.
Table 2. Age structure composition of S. pseudaksaiensis.
AgeTurks River
NumberStandard Length/mmBody Weight/g
RangeMean ± S.D.RangeMean ± S.D.
12347.30~70.4461.03 ± 7.591.59~4.983.52 ± 1.09
28453.82~97.5779.348.16 ± 7.022.69~11.517.69 ± 1.86
33886.30~133.12110.39 ± 10.3210.00~27.4320.56 + 4.54
417126.33~166.84148.79 ± 10.5430.10~58.1146.97 ± 8.01
552155.17~198.44177.92 ± 9.1159.30~150.0083.61 ± 14.41
692167.61~235.00208.02 ± 13.3781.82~200.00131.37 ± 18.16
7124204.00~264.17231.28 ± 11.55137.82~250.00192.99 ± 24.58
868242.00~285.06256.38 ± 10.01237.47~350.00270.04 ± 27.77
957252.00~301.91278.71 ± 11.07211.42~501.98336.63 ± 47.11
1049284.06~324.45301.12 ± 11.80306.54~550.00423.04 ± 37.04
1126302.41~340.96322.30 ± 9.14450.00~650.00522.03 ± 41.32
1223320.00~359.73342.26 ± 10.80548.42~800.00652.01 ± 70.36
1320344.37~369.77358.67 ± 7.30449.94~848.00721.74 ± 76.78
149360.00~394.00378.08 ± 11.90500.00~1000.00817.65 ± 142.81
157378.00~406.82497.22 ± 10.35850.00~1300.001016.60 ± 141.39
162406.00~408.00407.00 ± 1.411300.00~1350.001325.00 ± 35.36
177418.18~432.18427.25 ± 5.751159.38~1700.001423.99 ± 197.10
187436.38~451.70445.11 ± 5.481224.95~1764.741552.97 ± 168.03
1910453.06~467.10459.97 ± 4.881403.16~1755.681614.93 ± 113.78
204466.50~475.00472.78 ± 4.191520.36~1850.001692.59 ± 157.640
216475.53~485.00479.81 ± 4.451750.00~2300.002041.67 ± 205.95
224503.67~515.01509.58 ± 4.691850.00~2450.002112.50 ± 268.87
236530.74~538.60533.89 ± 2.732200.00~2850.002475.00 ± 238.22
Total73547.30~538.60232.62 ± 103.321.59~2850.00327.06 ± 440.90
Table 3. Comparison of otolith morphological index with AIC values of standard length.
Table 3. Comparison of otolith morphological index with AIC values of standard length.
ParameterLinear EquationLogarithmic EquationPower EquationExponential Equation
OA−388.81959−326.00457−837.21834−727.98510
Rmin−988.28599−1010.62538−1188.16460−1100.23007
Rmax−818.08214−807.90184−1217.95391−1107.54899
OP−164.87986−150.30386−1141.61319−1065.05038
OL−1230.35127−1221.03375−1224.43525−1117.13393
OW−1363.38737−1387.88444−1195.11009−1104.32348
Table 4. Comparison of otolith morphological index with AIC values of body weight.
Table 4. Comparison of otolith morphological index with AIC values of body weight.
ParameterLinear EquationLogarithmic EquationPower EquationExponential Equation
OA−376.26244−376.26244−887.08062−452.85771
Rmin−758.20313−1060.49461−1233.47752−860.31769
Rmax−520.14663−869.60714−1274.17292−806.49466
OP72.37525−211.98641−1198.64829−806.26546
OL−930.36584−1274.79386−1273.24277−816.98914
OW−1130.29426−1434.92895−1238.52020−858.82629
Table 5. Growth equations of the female and male populations of S. pseudaksaiensis.
Table 5. Growth equations of the female and male populations of S. pseudaksaiensis.
PopulationFemale (n = 350)Male (n = 389)
Lt737.7 [1 − e−0.05(t + 0.59)] (R2 = 0.9924)667.0 [1 − e−0.05(t + 0.36)] (R2 = 0.9829)
Wt6853.3[1 − e−0.05(t + 0.59)]3.0436 (R2 = 0.9651)4447.2[1 − e−0.05(t + 0.36)]2.9759 (R2 = 0.9707)
dL/dt35.9 e−0.05(t + 0.59)36.7 e−0.05(t + 0.36)
dW/dt1015.8 e−0.05(t + 0.59) [1 − e−0.05(t + 0.59)]2.0436725.3 e−0.05(t + 0.36) [1 − e−0.05(t + 0.36)]1.9759
dL2/dt2−1.7 e−0.05(t + 0.59)−2.0 e−0.05(t + 0.36)
dW2/dt249.5 e−0.05(t + 0.59) [1 − e−0.05(t + 0.59)]1.0436 [3.0436 e−0.05(t + 0.59) − 1]39.7 e−0.05(t + 0.36) [1 − e−0.05(t + 0.36)]0.9759 [2.9759 e−0.05(t + 0.36) − 1]
ti22.2819.55
Standard length/mm corresponding to ti520.17507.26
Body weight/g corresponding to ti2366.321943.33
Table 6. Relationship between absolute fecundity and standard length/body weight of S. pseudaksaiensis.
Table 6. Relationship between absolute fecundity and standard length/body weight of S. pseudaksaiensis.
ParameterLinear EquationLogarithmic EquationPower EquationExponential Equation
L−63.14150848340.538227340.0967467−66.56823424
W−49.30208045357.2521667339.9725195−57.66593688
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Wang, C.; Yao, N.; Xia, L.; Wang, X.; Song, Y.; Serekbol, G.; Zi, F.; Lin, X.; Yan, J.; Chen, S. Age, Growth and Reproduction of Schizothorax pseudaksaiensis of the Turks River. Water 2023, 15, 4044. https://doi.org/10.3390/w15234044

AMA Style

Wang C, Yao N, Xia L, Wang X, Song Y, Serekbol G, Zi F, Lin X, Yan J, Chen S. Age, Growth and Reproduction of Schizothorax pseudaksaiensis of the Turks River. Water. 2023; 15(23):4044. https://doi.org/10.3390/w15234044

Chicago/Turabian Style

Wang, Chengxin, Na Yao, Liwei Xia, Xinyue Wang, Yong Song, Gulden Serekbol, Fangze Zi, Xuyuan Lin, Jin Yan, and Shengao Chen. 2023. "Age, Growth and Reproduction of Schizothorax pseudaksaiensis of the Turks River" Water 15, no. 23: 4044. https://doi.org/10.3390/w15234044

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