Effects of sediment burial on grass carp,Ctenopharyngodon idella (Valenciennes, 1844), eggs

It is thought that grass carp (Ctenopharyngodon idella) eggs must remain suspended in the water column in order to hatch successfully. Using sand, the effects of varying sediment levels on grass carp eggs were tested at different developmental states and temperatures. Survival was high (15–35%, depending on temperature and trial) in the unburied treatment where eggs rested on a sand bed but were not covered by sediment. Survival was lower in the partial burial (5–10%) and very low (0–4%) in the full burial treatment. In all treatments, delayed hatching (organisms remaining in membranes past the stage of hatching competence) was noted. Deformities such as missing heads and pericardial edema occurred at high rates in the partial and full burials. Eggs that come in contact with the benthos and are resuspended in the water column should be considered in embryonic drift models.     

Morphology of androgenetic and gynogenetic grass carp, Ctenopharyngodon idella (Valenciennes)

Crosses between female carp x male grass carp resulted in androgenetic grass carp and hybrids. Fertilizing grass carp eggs with carp milt that had been irradiated with ultraviolet light for 15 min at 1.0 mW/cm² produced gynogenetic grass carp. We compared the morphology of experimental progeny with that of the parental species to determine if inheritance was strictly matroclinous in gynogenesis and strictly patroclinous in andro-genesis. Dorsal and anal fin rays, lateral line scales, gill rakers, pharyngeal teeth, and the relative length of the dorsal fin all suggested that gynogenetic grass carp were identical with the maternal species and androgenetic grass carp with the paternal species. Hybrids were intermediate between the parents except that the number of anal rays was identical with that in carp. The number of dorsal rays, the body depth, and the pharyngeal teeth in hybrids were more like those in carp than in grass carp, whereas the number of gill rakers was more similar to that in the paternal species.     

Temperature preference and heat resistance of grass carp, Ctenopharyngodon idella (Valenciennes), bighead carp, Hypophthalmichthys nobilis (Gray), and their F1 hybrid

Acute temperature preferenda and critical thermal maxima were determined for 23°C-acclimated stocks of grass carp, bighead carp and their F, triploid hybrid. Preferred temperature and critical thermal maximum of the hybrid were significantly higher than those of the grass carp (female parent), which is consistent with prior field observations. The hybrid's values for both parameters also were significantly higher than those of the bighead carp. These results comprise experimental evidence for substantial heterosis in the thermal physiology of fishes.     

Digestion of duckweed (Lemna spp.) by the grass carp (Ctenopharyngodon idella)

A feeding trial was conducted in 55-1 aquaria indoors with the grass carp ( Ctenopharyngodon idella Val.) using fresh duckweed ( Lemna spp.) as food. Faeces dry weight was closely correlated with dry weight of duckweed consumed based upon a linear regression. From this regression, the estimated true digestibility of dry matter was 65%. Samples of duckweed and fish faeces were analysed for crude protein and gross energy. Van Soest's Analysis was conducted on composite samples of duckweed and faeces. Apparent digestibilities were 80% for crude protein, 61% for gross energy, 72% for organic cell contents, and 30% for organic cell wall constituents.     

Effect of probiotic Bacillus subtilis Ch9 for grass carp,Ctenopharyngodon idella (Valenciennes, 1844), on growth performance,digestive enzyme activities and intestinal microflora

In the present study, Bacillus subtilis Ch9 was evaluated as a probiotic in grass carp, Ctenopharyngodon idella (Valenciennes, 1844). For 56 days the grass carp (50 ± 2.5 g) were given a feed containing B. subtilis Ch9 in three concentrations: 1.0 × 10⁹ (T₁), 3.0 × 10⁹ (T₂) and 5.0 × 10⁹ (T₃) CFU kg^?1 feed in triplicate treatments. The control group (T₀) was given feed without B. subtilis Ch9 for the same period. Determined were the specific growth rate (SGR), feed conversion ratio (FCR), and digestive enzyme activities in the intestine and hepatopancreas as well as the intestinal microflora. After 56 days, fish receiving the diets supplemented with B. subtilis Ch9 showed significantly higher SGR and lower FCR (P < 0.05) than those fed the control diet. There was no significant different in SGR and FCR among T₁, T₂ and T₃ nor was the survival rate affected (P > 0.05) by the dietary treatments. From days 14 to 56 of the experiment, higher protease, amylase and lipase activities in the foregut, midgut hindgut and hepatopancreas were observed in T₁, T₂ and T₃ (P < 0.05) compared with the control over a short‐term (14–28 days). Enzyme activity did not increase after long‐term feeding with B. subtilis Ch9 (56 days), but was still higher than that of control fish (P < 0.05). Fish fed the probiotic had an increase in trend of total aerobic and facultative anaerobic bacterial quantity (P > 0.05), but the ratio of Bacillus was significantly higher (P < 0.05) than in control fish. The total anaerobic bacterial quantity, Bifidobacterium and Lactobacillus were significantly higher (P < 0.05) in fish fed B. subtilis Ch9 compared with fish fed control feed. In conclusion, an optimum dose of B. subtilis Ch9 could modulate intestinal microflora, induce digestive enzyme activity and potentially promote the digestion and absorption of nutrients, as well as improve the growth performance of grass carp significantly.     

Intensive culture of grass carp, Ctenopharyngodon idella, in circular tanks

Fingerling grass carp ( Ctenopharyngodon idella ) were cultured in 380 1 circular fiberglass tanks at stocking densities of 0.53, 1.06, 1.59 and 2.11 fish/1. Fish were fed duckweed ( Lemna minima ) to satiation. Fish grew from 2.7 g to a maximum mean weight of 72.7 g in 88 days. Fish stocked at 0.53 fish/1 grow more rapidly than those stocked at higher densities. Mean daily consumption rates were strongly correlated with oxygen levels and when oxygen levels dropped below 4 mg/1 consumption was reduced approximately 40%. High biomass, growth, and survival rates obtained during this study indicate grass carp are well suited for intensive tank culture.     

Olfactory sensitivity of the herbivorous grass carp, Ctenopharyngodon idella, to amino acids

The olfactory sensitivity of a herbivore, the grass carp, Ctenopharyngodon idella , to ten amino acids was investigated using electrophysiological recording techniques. Underwater electroolfactogram recordings increased exponentially with logarithmic increases of stimulus concentration from threshold to 1 × 10⁻³ m. Calculated detection thresholds ranged from 1 × 10^−7.15 m to 1 × 10^−8.7 M and are similar to those previously reported for carnivorous fish species. The relative stimulatory efficacy (RSE) of the ten amino acids determined at 1 × 10⁻⁴ M revealed five groups of stimuli, with cysteine the most stimulatory and proline the least. Measures of amino acid RSE did not differ significantly from those of previously studied carnivores, except for arginine. Grass carp showed strong responses to this compound, whereas it has produced only limited responses in carnivores. Differences in the responsiveness of herbivores and carnivores were not observed, suggesting that feeding niche segregation is probably not facilitated by differential olfactory sensitivities to feeding stimuli.     

A note on the effect of lowered temperatures on the survival of eggs and fry of the grass carp Ctenopharyngodon idella (Valenciennes)

The grass carp has been introduced into many countries and yet self-sustaining populations are known at four sites only outside its natural range. While the hydrological conditions apparently necessary for spawning are unlikely to occur in the U.K. the requirements of temperature and perhaps water speed occur locally in heated effluents from power stations. Since most heated effluents tend to layer on the water surface, grass carp eggs laid in effluents would quickly be exposed to falls in temperature of up to about 9°C. Experiments carried out in Austria with newly fertilized eggs show that incubation temperatures below 20°C result in large scale deaths, and deformities which lead to death, although 20 h old fry are not adversely affected. Because summer river temperatures seldom exceed 20°C it is concluded that if spawning did occur it would be unsuccessful at most power station sites. At sites where the power station uses a considerable proportion of the available river flow and where the effluent mixes completely downstream, eggs could possibly survive if temperature were the major criterion for successful development.     

Morphological comparisons of diploid and triploid hybrid grass carp, Ctenopharyngodon idella♀×Hypophthalmichthys nobilis♂

Morphological and karyological comparisons of 25–28 hybrid grass carp from each of 3 year-classes (1979–1981) indicated that diploid fish resulted during 1979 (82.1%) and 1980 (76.0%) the others being triploid. All of the fish tested from the 1981 year-class were triploid. Most triploid fish differed from diploid fish by having a faster growth rate, fewer scales in the lateral line and transverse series below the lateral line, a relatively longer gut, and fewer deformities.     

The tolerance of grass carp, Ctenopharyngodon idella Val., to aquatic herbicides

Because grass carp may feed selectively on water plants, additional conventional methods may be necessary for effective control of aquatic vegetation. For economic reasons aquatic herbicides are most likely to be used in conjunction with grass carp within an integrated aquatic weed control programme. The acutely lethal toxicities of ten herbicides to grass carp were measured. A preliminary evaluation of the risk to these fish showed that, when used at the recommended rate, the maximum herbicide concentration likely to be found in water should cause little harm to the fish, although attention should be given to the possible inhibition of feeding.     

Relationship between the chemical composition of aquatic macrophytes and their consumption by grass carp, Ctenopharyngodon idella

The rate at which triploid grass carp, Ctenopharyngodon idella , consumed two plant species from different locations was measured and compared to the chemical composition of the plants. Grass carp fed on Elodea canadensis from three lakes at significantly different rates ( P > 0.001), but did not eat Elodea densa from two of the sites at different rates. Feeding rate of the grass carp was positively correlated to the concentration of calcium ( r = 0.976) and lignin ( r = 0.946), but negatively correlated to the content of iron ( r =−0.808), silica (r=-0.934) and cellulose ( r =−0.922). Multiple regression analysis revealed that calcium and cellulose content were the most important predictors of consumption rate. These experiments demonstrate that water chemistry may affect palatability and could in part be responsible for some of the discrepancies in grass carp consumption rate and preference studies.     

Characterization of oligopeptide transporter (PepT1) in grass carp (Ctenopharyngodon idella)

The oligopeptide transporter (PepT1) is located on the brush-border membrane of the intestinal epithelium, and plays an important role in dipeptide and tripeptide absorptions from protein digestion. In this study, we cloned the PepT1 cDNA from grass carp and characterized its expression profile in response to dietary protein and feed additives (sodium butyrate) treatments. The PepT1 gene encodes a protein of 714 amino acids with high sequence similarity with other vertebrate homologues. Expression analysis revealed highest levels of PepT1 mRNA expression in the foregut of grass carp. In addition, PepT1 mRNA expression exhibited diurnal variation in all three bowel segments of intestine with lower levels of expression in daytime than nighttime. During embryonic development, PepT1 showed a dynamic pattern of expression reaching maximal levels of expression in the gastrula stage and minimal levels in the organ stage. The PepT1 expression showed constant levels from 14 to 34 day post-hatch. To determine whether fish diet of different protein contents may have any effect on PepT1 expression, we extended our research to dietary regulation of PepT1 expression. We found that dietary protein levels had a significant effect on PepT1 gene expression. In addition, PepT1 mRNA levels were higher after feeding with fish meal than with soybean meal. Moreover, in vitro and in vivo sodium butyrate treatments increased PepT1 expression in the intestine of grass carp. The results demonstrate for the first time that PepT1 mRNA expression is regulated in a temporal and spatial pattern during development, and dietary protein and feed additives had a significant effects on PepT1 gene expression in grass carp.     

草鱼胶原凝集素基因的克隆及其功能分析

从草鱼Ctenopharyngodon idella肝肾cDNA文库中克隆得到胶原凝集素基因。草鱼胶原凝集素全长cDNA为1128bp,其中5′非编码区229bp,3′非翻译区104bp,最大开放阅读框为795bp,编码264个氨基酸。系统进化分析表明草鱼胶原凝集素与斑马鱼的亲缘关系最近。根据草鱼胶原凝集素序列特征,克隆了包含糖基识别域(CRD)的cDNA,并进行原核表达、纯化获得其重组蛋白PCRD。进行PCRD与6种细菌的凝集和糖抑制实验,结果表明半乳糖、葡萄糖、甘露糖和麦芽糖4种糖都会使PCRD与嗜水气单胞菌的凝集明显下降甚至极大地干扰凝集;麦芽糖使金黄色葡萄球菌的凝集明显下降,而肽聚糖和甘露糖会使凝集受到抑制;此外,PCRD的凝集反应不依赖Ca2+。     

The tolerance of grass carp Ctenopharyngodon idella (Val.) to seawatert†

Laboratory tests were conducted to determine the tolerance of 2+ grass carp to an oceanic water. It was found that at a temperature of 20.1°C±0.4°C the maximum survival times of the fish in concentrations of seawater equivalent to 17.5 and 10.5 g/1 sodium chloride were 5 h and approximately 24 days respectively. The importance of these results lies in the consideration of the possibility of grass carp migrating through brackish or seawater from one river system to another. Such a migration would seem to be impossible through seawater but may be possible through brackish water.     

Temperature preference and tolerance of hybrid carp (female grass carp,Ctenopharyngodon idella x male bighead,Aristichthys nobilis)

Synopsis This study examined the effects of various pH values on sperm motility times of white suckers,Catostomus commersoni, from two artificially acidified lakes in the Experimental Lakes Area (ELA), northwestern Ontario. White sucker sperm were active (motile) in water at all pH values tested (3.0–7.0). The maximum sperm motility time was 76.9 seconds and the minimum time was 51.9 seconds. Sperm motility times of fish from Lake 302N were similar to those of fish from Lake 223 at all pH values except pH 5.0 and 5.5. At these two pH values, sperm motility times of Lake 223 fish were longer than those of Lake 302N fish. In both lakes sperm motility at ambient lake pH levels (Lake 223 + 5.1, Lake 302N + 6.3) were similar to those at pH 7.0. Motility times of all fish tested were within the range of time during which fertilization normally occurs, indicating that reproductive failures in Lake 223 were probably not caused by impairment of sperm motility times.     

Comparison of early developmental stages and adults of grass carp, Ctenopharyngodon idella, and hybrid carp (female grass carp × male bighead Aristichthys nobilis)

Hybrid carp and grass carp from the zygote to the prolarval stage and adults were compared to establish distinguishing characteristics. Zygote diameter, yolk sac and embryo length were not different between the fishes. Body pigmentation patterns showed distinct separation among the prolarvae of the hybrids and grass carp. Total and preanal myomeres were higher in grass carp larvae than in the hybrids. The grass carp and hybrid larvae also differed in 38% of the proportional morphometric characters.
Average meristic counts of adults were significantly higher in hybrids compared with grass carp. Adults of the two fishes showed significant differences in 63% of the proportional morphometric measurements. Gill raker counts showed no overlap and lateral line scales were smaller and more numerous in the hybrid adults.     

How the grass carp (Ctenopharyngodon idella) chooses and chews its food—some clues

Grass carp were allowed to feed on a variety of plants, presented one species at a time. They were filmed and their faeces collected. Canadian pondweed, a grass and a filamentous alga were readily taken; greater duckweed, shining pondweed and the leaves of reedmace were not so acceptable. Limiting factors in feeding seem to vary: with the two pondweeds foraging is limiting, probably because the leaves make it difficult for the fish to extract a single, manageable stem. Transport is limiting with the grass—the fish cannot swallow it quickly enough. Chewing is limiting with reedmace leaves (they are too tough) and the filamentous alga (for no apparent reason). Duckweed is rejected, probably because it has an unpleasant taste. All plants are chewed at the same frequency of jaw movement, independent of the texture of the plant.