Percocypris Pingi Research Articles

Comparative study on the blood physiological, biochemical indexes and liver histology of Schizothorax wangchiachii (♀), Percocypris pingi (♂) and their hybrids

Comparative study on the blood physiological, biochemical indexes and liver histology of Schizothorax wangchiachii (♀), Percocypris pingi (♂) and their hybrids

Host habitats influence the gut microbial assembly mechanisms of cold-water fish

Due to factors such as overfishing, hydropower development, and water pollution, their wild populations have drastically declined, with many species being classified as endangered or vulnerable. Understanding the driving factors behind the gut microbiota of cold-water fish holds significant implications for conservation. Therefore, to investigate the influence of different factors on the gut microbes of cold-water fish, 112 gut samples from farmed and wild habitats were collected from Schizothorax wangchiachii (herbivorous), Schizothorax kozlovi (omnivorous) and Percocypris pingi (carnivorous), in the Jinping Dahewan range of lower reaches of the Yalong River. The results of 16 S rRNA gene sequencing of the gut contents showed that habitat was the major factor influencing the gut microbes of the three cold-water fishes. In terms of microbial composition, farmed cold-water fish exhibited a dominant bacterial phylum, Proteobacteria (82 %), while those in wild environment presented multiple dominant taxa, such as Proteobacteria (38 %), Fusobacteria (30 %), Firmicutes (11 %), and Cyanobacteria (11 %). Gut microbial diversity, both α diversity and β diversity, in wild cold-water fish was significantly higher than that in farmed individuals. Network complexity of gut microbiota was notably higher in wild cold-water fish than in farmed individuals. From farmed to wild environments, the relative influence of deterministic processes in the gut microbiota assembly mechanism of cold-water fish gradually diminishes, while the contribution of stochastic processes steadily increases. The gut microbiota construction mechanism in farmed cold-water fish was primarily influenced by deterministic processes of homogeneous selection, while in wild cold-water fish, it was mainly driven by stochastic processes of homogeneous dispersal. Overall, this study is an important reference for the study of the gut microbiota of cold-water fish and the conservation of their wild populations.

Changes in fish resources 5 years after implementation of the 10-year fishing ban in the Chishui River, the first river with a complete fishing ban in the Yangtze River Basin

BackgroundTo rehabilitate the depleted fish resources of the Yangtze River Basin, China, a 10-year fishing ban has been implemented. This national initiative has attracted worldwide attention. The present study aimed to explore the ecological process and recovery effectiveness of this complete fishing ban in the Chishui River, the first river where the fishing ban was enacted in the Yangtze River Basin. Changes in fish resources were analyzed based on investigations conducted 5 years before (2012–2016) and 5 years after (2017–2021) the implementation of the fishing ban in four reaches along the longitudinal gradient.ResultsA total of 140 fish species, including 127 native and 13 exotic species, were collected during the study period. The number of fish species as well as the diversity indices showed no significant temporal changes. However, 11 native species that had disappeared for many years appeared again after the fishing ban. The occurrence rates of some key protected species, Procypris rabaudi, Acipenser dabryanus, Euchiloglanis davidi and Myxocyprinus asiaticus, increased after the fishing ban, while Coreius guichenoti, Percocypris pingi, Onychostoma angustistomata and Leptobotia rubrilabris showed no obvious recovery. The fish assemblage structure in nearly all reaches (except the headwater) showed significant temporal changes with an increase in the relative abundance of larger body-sized species. The population structure of most dominant species improved greatly with the mean standard length and the mean body weight as well as the proportion of larger-sized individuals clearly increasing. In addition, the density of fishes changed dramatically with the catch per unit effort (CPUE) increasing by 140–210% for different study reaches.ConclusionsThe present study confirmed that the complete fishing closure is an effective measure to facilitate fish resources recovery. These results provide valuable references for evaluating the effectiveness of the 10-year fishing ban policy in the entire Yangtze River.

Fish entrainment model for decision support in ecosystem management: A case study from China's Maling Reservoir

Fish entrainment from reservoirs to downstream rivers by various water release structures may result in serious consequences for reservoir ecosystems. This study proposed an integrated modeling approach for determining fish entrainment risk zones and suitable reservoir regulations. The modeling approach combines hydrodynamic and fish risk assessment modeling with using fuzzy rules set defined by expert knowledge in fish ecology. We applied this modeling approach in the Maling Reservoir in China, where fish entrainment in the reservoir has been observed in the turbine, spillway, and irrigation system. Percocypris pingi (Tchang, 1930) and Onychostoma simum (Sauvage & Dabry de Thiersant, 1874), representing the main and protected fish species, were selected as target fish species. Five reservoir operation schemes were investigated under normal and designed water levels. The modeling results suggest that the fish entrainment risk for protected fish species (Onychostoma simum) is higher than that for the main fish species (Percocypris pingi). The results indicate a ranking of the fish entrainment risk from high to low in the following scenarios: with all spillways in operations, with one spillway in operation, with intakes in operation, with an irrigation system in operation, and with intakes and the irrigation system in combined operations. In addition, under normal and designed water levels, dead fish entrainment zone areas and percentages were extremely low compared to the entire forebay of the reservoir. These results indicate that the operation of the Maling Reservoir does not affect the ecological status of fish. These findings are generally applicable to any fish species in reservoirs that balance reservoir operations and ecological protection of fish, and could assist reservoir managers in making informed decisions on how to mitigate and compensate for fish entrainment.

Continuous flow stimulation had no significant effect on the growth rate but was conducive to the swimming performance, spontaneous behavior, and nonspecific immune parameter of juvenile Percocypris pingi.

Flow stimulation before release into the wild may contribute to improved survivability of farmed fish. However, the effects of flow stimulation on the survival rate of fish depend on the fish species and exercise regime, such as exercise type, duration, and intensity. In this study, juvenile Percocypris pingi swam for 18 h per day for 8 weeks under different water speeds, 3 cm s-1 (control) and 1, 2, and 4 body lengths (bl) s-1 , at 20°C. Then, parameters related to the growth rate, swimming capacity, spontaneous activity, and immune function were measured. We found that (1) continuous flow stimulation had no significant influence on the growth but was conducive to the increase in the relative carcass mass; (2) continuous flow stimulation at 2 or 4 bl s-1 enhanced the aerobic swimming capacity (Ucrit ), which may be due to an increase in anaerobic exercise capacity (endurance time) rather than to changes in maximum metabolic rate and aerobic scope; (3) continuous flow stimulation at 4 bl s-1 led to a significant increase in spontaneous activity, which was mainly due to the higherpercent time spent moving as compared with the controls; and (4) continuous flow stimulation at 2 bl s-1 may contribute to improving the nonspecific immune parameter (lysozyme activity) in juvenile P. pingi. Our findings suggest that continuous flow stimulation at 2 or 4 bl s-1 for 18 h per day for 56 days at 20°C before release in wild may be a suitable training regime for improving the survival rate of cultured juvenile P. pingi.

First report of a CMTV-like ranavirus in farmed Percocypris pingi in China

Ranaviruses were recognized as important pathogens from the late 1990s, which are global pathogens that have continued to severely threaten aquaculture and wildlife worldwide. In this study, we report an infection with a CMTV-like ranavirus in cultured Percocypris pingi (P. pingi), a rare fish species that originated in upper Yangtze River system of China. Naturally and experimentally infected fish exhibited body surface ulcers and enlarged spleen and kidney. Histological examination revealed intracytoplasmic inclusions in the liver, spleen and kidney. Meanwhile, hexagonal viral arrays were observed in cytoplasm of infected Epithelioma papulosum cyprini (EPC) cells. Animal experimental trials confirmed that this hexagonal virus, named P. pingi ranavirus (PPRV), was the causative agent. PPRV (Accession no. ON080858) contains a 106.7 kbp genome, with a GC content of 55.03% and 97 ORFs. The results of phylogenetic analysis of the complete genome and dot plot comparisons both confirmed that the virus was classified into the CMTV-like group. Phylogenetic analyses based on MCP, mMMP, DNA polymerase and ribonuclease III genes indicated that PPRV shared the nearest relationship to Triplophysa siluorides ranavirus (Accession no. FYL140220), Chinese giant salamander iridovirus (Accession no. KF512820) and Andrias davidianus ranavirus (Accession no. KF033124), which were from China. Amidst the expanding fish host range of CMTV-like ranaviruses, this is the first report of ranavirus infection in P. pingi.

Hybrids with heterosis possess a more diverse intestinal microbiome than that of carnivorous and herbivorous parental fishes in controlled conditions

The intestinal microbiome plays critical, interactive roles in host nutrition and metabolism and may be involved in the known growth advantage of hybrids. In a previous study, we obtained healthy F1 hybrids (PS) by crossing carnivorous Percocypris pingi (PP, male) and herbivorous Schizothorax wangchiachii (SW, female) and found that the PS hybrids exhibited a growth advantage and that their feeding traits were similar to those of omnivorous S. davidi (SD). In this study, we compared the intestinal histology and anatomy of four fish lines (PP, PS, SW, SD) and, using 16S rRNA gene sequencing, constructed a map of their intestinal microbiome to explore host-influenced intestinal microbiome community composition among them under the same diet. We found that the intestinal anatomical and histological traits of PS and SD were similar, and intermediate between PP and SW, but closer to SW. Although PS and SD have similar feeding traits, their intestinal microbiome composition varied remarkably and, notably, the SD microbiome was closer to that of SW, indicating that phylogenetic effects may play a stronger role in gut microbiome development than the effects of feeding traits. Cetobacterium and Aeromonas were the predominant components of the intestinal microbiome in the four fishes, the former was more abundant in PP, and the latter was more abundant in SW and SD. The relative abundances of Cetobacterium and Aeromonas were lower in PS than in the other three fish lines, but the relative abundances of other microorganisms were generally higher in the PS microbiome, which led to more OTUs and higher alpha diversity. In addition, trypsin activity and amylase activity were strongly positively correlated with the relative abundance of Cetobacterium and Aeromonas, respectively. Although the digestive enzyme activities of PS showed hybrid weakness, its intestinal microbial diversity was higher, which may be related to its growth advantage.

Implications of postzygotic ecological isolation for reducing the ecological risks of escaped hybrids: A case of hybridization between carnivorous and herbivorous cyprinid fishes

Distant hybridization is an important breeding method in aquaculture. However, hybrid escape is frequent in aquaculture and may have a negative impact on indigenous species. In addition to reducing the fertility of hybrids, inhibiting their wild viability can also play a role in avoiding the ecological risk of escaped hybrids. Postzygotic ecological isolation refers to the phenomenon of reduced adaptation of hybrids in the parent environment (wild), such as the incompatibility between their phenotypes and their behavior or food resources, which suggests that differences in parental feeding habits may also weaken the adaptability of the hybrids in the wild. In this study, we compared external and skeletal traits related to feeding habits in carnivorous Percocypris pingi (PP), herbivorous Schizothorax wangchiachii (SW), their F1 hybrids (PS), and omnivorous S. davidi (SD). Then, we selected fish, shrimp, chironomid larvae, and periphytic algae as food resources corresponding to different ecological niches and carried out a short-term single-food feeding experiment (sufficient food) under monoculture and a 60-day mixed-food feeding experiment (limited food) under polyculture. We found that PS and SD had similar traits, which were intermediate between those of PP and SW. In the single-food experiment, PS and SD had no significant difference in the foraging level of the four food resources, and they showed little foraging for fish and algae. However, SD showed stronger competitive ability than PS under polyculture (feeding chironomid larvae). In the 60-day ecological simulation experiment, PS could barely forage for fish and shrimp, and its ecological niche was close to that of SW. PS did not gain weight during the experiment, which indirectly reflected its low adaptability in the wild. In summary, the concept of postzygotic ecological isolation was introduced into aquaculture for the first time in this study. Moreover, this study also suggests that reducing the ecological risk caused by the escape of transgenic and genome edited varieties can not only by reducing their fertility, but also by reducing their ecological adaptability, which may lead to their elimination at the larval stage in the wild. This provides new insights for the genetic containment of genetically improved varieties.

Effects of Water Temperature on the Growth, Antioxidant Capacity, and Gut Microbiota of Percocypris pingi Juveniles

It is necessary to determine the optimal temperature for Percocypris pingi growth in recirculating aquaculture systems. To describe the effects of temperature, we evaluated the growth, antioxidant enzyme activity, and gut microbiota structure of P. pingi at different temperatures, including 14, 18, 22, and 26 °C. Results showed that increases in body weight of individuals of the groups subjected to 18 and 22 °C temperatures were considerably higher than those in the groups subjected to temperatures of 14 and 26 °C between 20 and 60 d after the experiment started. Acid phosphatase activity in the liver and kidneys of P. pingi did not differ significantly among the various temperature groups (p > 0.05). A gradual restoration of the alkaline phosphatase and superoxide dismutase activities to variations in the surrounding temperature was observed in the liver and kidney of P. pingi. Interestingly, the water temperature did not affect the α-diversity or composition of the gut microbiota of P. pingi. In conclusion, water temperatures between 14 and 26 °C significantly impacted the growth of P. pingi (p < 0.05) but not the liver and kidney antioxidant capacity or the gut microbiota within 60 d.

Hybridization with Percocypris pingi male can improve the cultivation characteristics of snow trout (Schizothorax wangchiachii), especially the resistance to white spot disease (Ichthyophthirius multifiliis)

Snow trout (Schizothorax) is an important cold-water economic fish in Asian aquaculture, but it has some disadvantages, such as slow growth rate, weak resistance to white spot disease (Ichthyophthirius multifiliis) and high temperature, etc. In contrast, their sister genus, Percocypris, has stronger resistance to white spot disease and high temperature. Distant hybridization can integrate the advantages of both parents, so we attempted to cross S. wangchiachii with P. pingi to obtain F1 hybrids combining the advantages of both parents. Hybridization between P. pingi males and S. wangchiachii females was successful, but backcrossing failed. To explore the cultivation characteristics of hybrid fish, the growth performance, digestive enzyme activity, nutrient composition, gonad development, high temperature tolerance, and white spot disease resistance of hybrid fish and their parents were compared. In growth, a total of 18-week culture experiment (20 °C) were carried out, and the body weight of hybrid fish at 18 weeks (26.13 ± 7.34 g) was significantly higher than that of P. pingi (16.65 ± 6.82 g) and S. wangchiachii (16.05 ± 5.93 g). In digestive enzyme activity, the hybrid fish showed hybrid weakness, but there was no correlation between the digestive enzyme activity and body weight of the hybrid fish and its parents, indicating that the digestive enzyme activity could not reflect the growth differences. In nutritional composition, P. pingi had a higher crude protein content, S. wangchiachii had a higher crude lipid content, and both contents of hybrid fish were closer to those of P. ping. The relative contents of amino acids of the three fishes were similar, while the relative contents of polyunsaturated fatty acids were higher in hybrid fish and P. ping, and their relative content of fishy substances was lower than that of S. wangchiachii. In high temperature tolerance, the mortality temperature of P. ping (33.48 ± 0.39 °C) and hybrid fish (33.00 ± 0.92 °C) was significantly higher than that of S. wangchiachii (31.24 ± 1.07 °C). In tolerance to white spot disease, the hybrid fish showed a significant increase in resistance compared to S. wangchiachii and was almost free of I. multifiliis. In gonad development, the spermatic cells of the pentaploid hybrid fish remained in the spermatocyte stage without spermatozoa, their ovarian cells were lowly differentiated, and these characteristics were sterile phenotypes. In conclusion, hybridization with male P. ping can improve the cultivation characteristics of S. wangchiachi through preliminary research, providing a new perspective and reference for snow trout breeding.

High resistance to Ichthyophthirius multifiliis in Percocypris pingi, an endemic fish in upper Yangtze River

Ichthyophthirius multifiliis is a ciliated ectoparasite that infects almost all freshwater fishes with low host specificity. However, an endemic fish in the upper Yangtze River, Percocypris pingi, was thought by aqua-culturists to be completely resistant to I. multifiliis. We therefore aimed to determine P. pingi resistance to I. multifiliis. We compared the survival, feed intake, infection intensity, relative number of I. multifiliis tomont and tomont diameter, and the short- (2 months) and long-term (7 months) effects of I. multifiliis on growth between P. pingi, southern catfish (Silurus meridionalis), grass carp (Ctenopharyngdon idella), Schizothorax prenanti and Culter alburnus post I. multifiliis infection at 20,000 theronts/fish under controlled laboratory conditions. We also tested serum and skin mucus immobilization activity to I. multifiliis in uninfected individuals of the five fish species. The results detected mild I. multifiliis infection in P. pingi reflected by significantly lower parasite density and no expression of parasite I-antigen gene IAG52A comparable to the four other species. The low total relative number of tomonts collected from P. pingi during almost the entire parasitic stage (from the third to sixth day post infection) and small tomont size during the later parasitic stage (the fifth and sixth day post infection) suggest that P. pingi was able to limit trophont settlement and/or development. When infected by I. multifiliis, P. pingi displayed almost no mortality compared to high mortality in the other four fish species (14 days post infection) and surviving individuals recovered from the initial appetite loss within seven days post infection and represented normal growth over the following two and seven months. Furthermore, P. pingi mucus and serum have strong immobilization activity to I. multifiliis. It appears that P. pingi is highly resistant to I. multifiliis and may be a good model to understand the underlying immune mechanism of fish to I. multifiliis.

Host Species Influence the Gut Microbiota of Endemic Cold-Water Fish in Upper Yangtze River

The fish gut microbiome plays an important role in nutrition absorption and energy metabolism. Studying the gut microbes of cold-water fish is important to understand the dietary adaptation strategies in extreme environments. In this study, the gut samples of Schizothorax wangchiachii (SW, herbivorous), Schizothorax kozlovi (SK, omnivorous), and Percocypris pingi (PP, carnivorous) in the upper Yangtze River were collected, and we sequenced 16S rRNA amplicon to study the potential relationship between gut microbes and host species. The results showed that gut microbial composition and diversity were significantly different between the three cold-water fishes. These fishes had different key taxa in their gut microbes, including bacteria involved in the breakdown of food (e.g., Cetobacterium, Aeromonas, and Clostridium sensu stricto 10). The highest alpha diversity indices (e.g., Chao 1 index) were identified in the herbivore (SW), followed by the carnivore (PP), and the lowest in the omnivore (SK). Non-metric multidimensional scaling (NMDS) results revealed that the gut microbial community of these species was different between host species. The neutral community model (NCM) showed that the microbial community structure of SW was shaped by stochastic processes, and the highest species dispersal was found in SW, followed by PP, and the lowest in SK. The results of niche breadth agreed with these findings. Our results demonstrated that host species influenced the gut microbiome composition, diversity, and microbial community assembly processes of the three cold-water fishes. These findings implied that the variation of gut microbiome composition and function plays a key role in digesting and absorbing nutrients from different foods in cold-water fish.

Examining differentiation of sympatricSchizothoraxfishes reveals low differentiation in internal compared to external feeding traits

AbstractIn the process of sympatric species differentiation, which feeding traits are most differentiated? The complete feeding process of capture, ingestion, and digestion requires certain external, as well as internal traits. Therefore, comprehensive comparisons are needed to study fish feeding habits. This study systematically investigated the adaptive radiation and parallel evolution ofSchizothoraxfishes, and quantified the external, frame, pharyngeal bone, and digestive traits of the systematically differentiated omnivorousSchizothorax davidiand herbivorousS. wangchiachii. A member of their sister genus, the carnivorousPercocypris pingi, was used as an outgroup control to explore the feeding differentiation of sympatricSchizothoraxfishes. The results showed that these species had highly differentiated external traits, while the internal traits (pharyngeal bone and digestive traits) showed low differentiation, indicating that predatory traits diverged first in the differentiation of sympatricSchizothoraxfishes, while chewing and digestive traits were slower to diverge. Furthermore, we screened 16 continuous feeding traits, and the quantified values of these traits progressively increased or decreased with increasing nutritional level of food. These findings provide a reference for the selection of quantitative indicators in future studies of sympatric species differentiation.

Effect of predation‐risk and foraging opportunities on substrate choice and strength of brightness preference inSchizothorax wangchiachiiandPercocypris pingijuveniles

Fish substrate preference may be largely influenced by genetics. However, does predator-experience training (hatchery-reared fish exposed to their natural predators while in captivity) or the presence of conspecifics, prey or predator affect this preference? We determined the effect of predation-risk and foraging opportunities on substrate choice of Schizothorax wangchiachii and Percocypris pingi when in the presence of a conspecific, predator or prey. We found that both S. wangchiachii and P. pingi juveniles preferred the large gravel substrate, regardless of prey/predator presence or previous training. When in the presence of a predator, wild and predator-trained hatchery-reared S. wangchiachii juveniles chose the white substrate over the black substrate as it was the furthest away from the predator (Silurus meridionalis), whereas the predator-naïve individuals preferred the black substrate. This suggests that predation stress training could improve the ability to recognize and avoid predators in hatchery-reared S. wangchiachii juveniles. Wild and hatchery-reared P. pingi juveniles continued to choose the black substrate even though it was distant from the potential prey (S. wangchiachii). The time spent by wild P. pingi juveniles over black substrate was significantly lower than hatchery-reared juveniles. It is possible that the wild P. pingi juveniles' ability to recognize prey resulted in their more frequent movement towards the prey. The findings in the present study may lead to better predator/prey-recognition training of hatchery-reared S. wangchiachii and P. pingi juveniles, potentially increasing their survival rate when released to the wild.

Contrasting\xa0ecological niches lead to great\xa0postzygotic ecological isolation: a case of hybridization between carnivorous and herbivorous cyprinid fishes

BackgroundPostzygote isolation is an important part of species isolation, especially for fish, and it can be divided into two aspects: genetic isolation and ecological isolation. With the increase in parental genetic distance, the intensity of genetic isolation between them also increases. Will the increase in parental ecological niche differences also lead to the increase in ecological isolation intensity between them? This question is difficult to answer based on the current literature due to the lack of hybridization cases of contrasting ecological niche parents.ResultsCyprinid fish parents (Schizothorax wangchiachii and Percocypris pingi) with contrasting ecological niches (herbivorous and carnivorous) and their F1 hybrids were used as research objects. Fish and periphytic algae were selected as food corresponding to different parental resources. The foraging-related traits of these hybrids are generally the same between parents; however, the intermediate foraging traits of hybrids did not result in intermediate foraging performance for parental resources, and these hybrids could hardly forage for parental resources. The poor foraging performance of these hybrids for parental resources was caused not only by the decline in the foraging ability of these hybrids but, more importantly, by the decrease in foraging activity. Interestingly, these hybrids initially showed a high interest in foraging small fishes; however, after the first successful capture, these hybrids had difficulty ingesting fish and spit them out, which led to the subsequent decrease in foraging activity. We designed a series of experiments to explore the mechanism of the fish spitting of these hybrids, excluding the taste and the size of prey, and found that the decrease in their pharyngeal tooth puncture ability may be the reason.ConclusionsThis study was the first to demonstrate that these parents with contrasting ecological niches will produce great postzygotic ecological isolation for parental resources. The poor foraging performance of these hybrids for parental resources is mainly due to the decrease in foraging activity. Interestingly, these hybrids have obvious fish-spitting behaviour, which is a typical example of the incompatibility between intermediate traits and genetic behaviors.

Length‐weight and length‐length relationships of three fish species from the lower Yalong River, China

Length-weight relationships (LWRs) and length-length relationships (LLRs) were evaluated for three endemic fish species sampled from the lower Yalong River and its biggest tributary (the Anning River), in China. Specimens were captured using set gillnet (mesh size 4 cm) and backpack electro-fishing (power output 400 W, depth fished 1 m, area covered 3 m2) from June to July 2018. LWRs and LLRs are presented for the following species (Sinogastromyzon sichangensis, Micropercops swinhonis and Percocypris pingi).

Length‐weight relationships of four fish species from the Yalong River, China

Parameters of the length-weight relationship (LWR) were estimated for four fish species [Beaufortia szechuanensis (Fang, 1930), Claea dabryi (Sauvage, 1874), Percocypris pingi (Tchang, 1930), and Yunnanilus sichuanensis Ding, 1995] from the Yalong River. Samples were collected seasonally from June 2018 to July 2019, using various fishing gears [set nets (mesh: 1.5 × 2.0 cm), hook, drift gill nets (three mesh sizes: 1.0; 2.0; 3.0 cm) and electro fishing]. Two new maximum standard length were recorded for C. dabryi and P. pingi.

Substrate type and brightness preference ofSchizothorax wangchiachiiandPercocypris pingijuveniles

It is advantageous for fish to choose different substrate types and brightness based on their current life cycle stage, foraging requirements, predator avoidance and water conditions. We determined the substrate type and brightness preference of hatchery-reared and wild juvenile Schizothorax wangchiachii and Percocypris pingi under laboratory conditions. Individuals and groups were exposed to four kinds of substrate types (sand: diameter < 1 mm, small gravel: diameter approximately 2–3 cm, large gravel: diameter approximately 10–15 cm, sand and medium gravel mix: diameter approximately 4–7 cm) and two kinds of substrate brightness (black and white). The results showed that hatchery-reared and wild S. wangchiachii and P. pingi significantly preferred large gravel and black substrates regardless of the number of fish (p < .05). P. pingi had a significantly higher preference for black substrate than S. wangchiachii both in hatchery-reared and wild individuals (p < .05). Hatchery-reared and wild individuals of the two species shared a preference for large gravel and black substrates suggesting that substrate preferences might be genetically based. The findings in the present study could be used to improve the rearing conditions for the two species in hatchery and thereafter to enhance its adaptability after releasing to the wild.

Rheotaxis and swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and application to design of fishway entrances

The objective of this research was to determine the effects of diel cycle and flow velocity on rheotaxis, measure the swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and use the results to recommend an appropriate fishway entrance velocity and fish lift operating schedule. PIT tagging was used to monitor fish rheotaxis for 48 h in four channels with differing flow characteristics. Swimming performance tests were conducted in a swimming respirometer and induced flow speed, critical swimming speed and critical burst speed were determined. The relationship between flow velocity and fish swimming behavior was analyzed to determine the optimal attraction flow velocity. There were three primary findings. (1) Test fish were active both day and night, but made more attempts, had longer retention times, and swam longer through-water distances in all channels during the day. (2) Entry, retention, and effort were maximum at a flow velocity of 0.2 m/s (26% of absolute critical swimming speed (m/s) and 29% of relative critical swimming speed (bl/s)). (3) Attempt number, retention time and through-water distance increased with body length in the channel with greatest activity. Collectively, these data suggest that passage of P. pingi will be optimized by fishways operating throughout the day and most of the night, although these conditions could lead to size-based selectivity in passage.

Genetic and morphology analysis among the pentaploid F1 hybrid fishes (Schizothorax wangchiachii ♀ × Percocypris pingi ♂) and their parents

Triploid and pentaploid breeding is of great importance in agricultural production, but it is not always easy to obtain double ploidy parents. However, in fishes, chromosome ploidy is diversiform, which may provide natural parental resources for triploid and pentaploid breeding. Both tetraploid and hexaploid exist in Schizothorax fishes, which were thought to belong to different subfamilies with tetraploid Percocypris fishes in morphology, but they are sister genera in molecule. Fortunately, the pentaploid hybrid fishes have been successfully obtained by hybridization of Schizothorax wangchiachii (♀, 2n = 6X = 148) × Percocypris pingi (♂, 2n = 4X = 98). To understand the genetic and morphological difference among the hybrid fishes and their parents, four methods were used in this study: morphology, karyotype, red blood cell (RBC) DNA content determination and inter-simple sequence repeat (ISSR). In morphology, the hybrid fishes were steady, and between their parents with no obvious preference. The chromosome numbers of P. pingi have been reported as 2n = 4X = 98. In this study, the karyotype of S. wangchiachii was 2n = 6X = 148 = 36m + 34sm + 12st + 66t, while that the hybrid fishes was 2n = 5X = 123 = 39m + 28sm + 5st + 51t. Similarly, the RBC DNA content of the hybrid fishes was intermediate among their parents. In ISSR, the within-group genetic diversity of hybrid fishes was higher than that of their parents. Moreover, the genetic distance of hybrid fishes between P. pingi and S.wangchiachii was closely related to that of their parental ploidy, suggesting that parental genetic material stably coexisted in the hybrid fishes. This is the first report to show a stable pentaploid F1 hybrids produced by hybridization of a hexaploid and a tetraploid in aquaculture.