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Ctenopharyngodon idella (grass carp)
Abstract
This datasheet on Ctenopharyngodon idella covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Dispersal, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Management, Genetics and Breeding, Economics, Further Information.
Grass carp (Ctenopharyngodon idella) are globally important in aquaculture and aquatic vegetation control. However, escaped grass carp have established invasive populations. A targeted keyword search was performed on a carp (order: Cypriniformes) literature database maintained by the U.S. Geological Survey to identify literature relevant to grass carp. Additional sources cited in reviewed documents and provided by numerous reviewers were also included. There were three focus areas designed to provide support for invasive grass carp management: (1) diet and behavior; (2) physiological constraints, toxicity, and biology; and (3) gut physiology. Each focus area provides information to guide development of potential pathways for invasive grass carp control. Information from other carp species was used to fill in gaps where grass carp information was lacking and provide additional, potential research directions. Diet-related information included food selection and aquacultural diet formulations. Behavioral information included stimuli and non-physical barriers to attract, repel, or stop movement. Physiological constraints, toxicology, reproductive control, and biological control provide a research review for control options. Gut physiology and related control pathways provide knowledge to improve toxin or pathogen delivery. This review provides a basis for developing approaches and research for controlling invasive grass carp populations, aquaculture, and native population management.
In the present study we tested the effects of translocations from aquaculture facilities of grass carp, one of the most commonly used species in aquaculture globally, to constructed ponds in the Auckland region, New Zealand. Primarily, we were interested in whether zooplankton assemblages in recipient ponds are affected by the concomitant introduction of ‘hitchhikers’ with fish releases. Zooplankton community composition was quantified in 34 ponds that had been subject to grass carp release and 31 that had no grass carp introductions. A significant difference in zooplankton community composition was observed between ponds that had received grass carp translocations and those that had not. Differences in community composition between ponds with and without carp releases could be attributed to both the: (1) effects of activity of grass carp through habitat modification; and (2) establishment of hitchhiking zooplankton species originating from aquaculture ponds, including non-native species. Effective measures to curb the proliferation of non-native taxa within aquaculture facilities, and to mitigate the accidental movement of non-native taxa with translocations from these facilities, are required to reduce future zooplankton introductions.
Grass Carp (Ctenopharyngodon idella) has been introduced worldwide from its native range in
Eastern Asia. This species was first introduced in the United States in the early 1960s and has
since established reproducing populations in several major rivers of the United States. Impacts
associated with Grass Carp introductions include changes to aquatic vegetation and habitat,
community structure and processes, and water quality. Given its potential to invade Canadian
watersheds via waterways connected to the Mississippi River basin, live trade, or other
pathways, there is considerable concern for their potential ecological impacts if introduced to
Canada. Using information on Grass Carp biology, a risk assessment conducted by Fisheries
and Oceans Canada (DFO) in 2004 identified Grass Carp to be a high ecological risk to Canada
if introduced. Such risk assessments need to be adaptive, taking into account new approaches
and data. This biological synopsis is intended to update information on Grass Carp, specifically
focusing on the literature published between 2003 and early 2015, and will be used to inform a
binational Grass Carp risk assessment. Current knowledge on the distribution, taxonomy,
ecology and impacts of Grass Carp are outlined in this report, and includes details on the
longevity, physiological tolerance, diet, fecundity, adaptability, and dispersal potential of Grass
Carp where it has been studied.
The freshwater fish fauna of the Neotropics comprises one of the most diverse ichthyofaunas globally. The Iguaçu ecoregion of the Neotropics includes about 100 described species, of which ≈70% are endemic and the majority of these are considered to be threatened with extinction. As is the case in freshwaters worldwide, the Iguaçu ecoregion has been strongly impacted by a variety of factors, including urbanization, agriculture, the construction of dams and the introduction of non-native species. There is, however, a paucity of information on fish invasions and their impacts in the Iguaçu ecoregion. To address this knowledge gap an exhaustive literature review was conducted to determine the extent of introductions, the main vectors of introductions and the major risks associated with the introduction of non-native fish into the Iguaçu ecoregion. A total of 41 studies concerning non-native fish in the Iguaçu ecoregion were found, the majority (56.1%) from lists of species and first records of non-native species; while 29.3% of the studies only mentioned possible negative impacts of non-native species and 14.6% of studies evaluated, indirectly, the impacts of non-native species. The Iguaçu ecoregion has a long history of fish introductions, beginning with the first record of the “common carp” Cyprinus carpio in 1944, and continuing to the recent record, in 2012, of Steindachnerina brevipinna. Since 1944, 29 non-native species have been introduced, 19 from different ecoregions of the Neotropics, and 10 introduced from other zoogeographic regions (Ctenopharyngodon idella, C. carpio, Hypophthalmichthys molitrix, H. nobilis and Misgurnus anguillicaudatus from Palearctic region; Clarias gariepinus, Oreochromis niloticus and Tilapia rendalli introduced from Ethiopian region, and Ictalurus punctatus and Micropterus salmoides from Nearctic region). The main vector of introduction was aquaculture, with the aquarium trade, baiting, sport fishing and stocking also playing roles. Studies indirectly investigating the establishment and spread of the introduced species in the Iguaçu ecoregion found nine non-native species which were considered established. Moreover, studies evaluating the impact of non-native species have investigated changes in the feeding habits of non-native species, suggesting competition with native species for food resources, and the increase in the number of fish species introduced over time. The impacts of non-native fishes, often associated with other environmental changes, such as the construction of dams and pollution in the Iguaçu ecoregion, may have severe consequences for the endemic fish fauna, resulting in the further decline and potential extinction of native species.
Introductions of aquatic organisms into Japan are controlled only on the basis of the Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora and the quarantine acts. Up to 1986 more than 120 exotic species have been introduced, of which only 36 were made prior to 1945. Introductions are classified into four basic categories. In this paper of those in two categories, (i) species which have spread widely over Japan and are self reproducing, and (ii) those which have been maintained for generations through artificial propagation or in confined natural waters are dealt with.
Grass carp fry (0.04±0.01 g avg wt; 1.48±0.03 cm total length) were stocked into an earthen pond in June. Every week for twelve weeks, fifteen fish were sacrificed and the content of their guts was examined. At the first week, animal material represented 74% of the gut contents. From the second week onwards, plant material was higher (mean value 79%). In the seventh week, when grass carp reached 4.83±0.09 cm, filamentous algae were replaced by macrophyte fragments. Besides the macrophytes, animal material such as the rotifers Monostyla and Lecane and the cladoceran Bosmina were found and the proportion of animal material in the gut varied 11-26%.
This study presents the history of the introduction of fish species into the freshwater system of Israel. Forty fish species, subspecies and hybrids were either stocked directly into freshwater bodies or raised in commercial fishponds and had access to escape routes into the natural freshwater system. Included in this study are escapees from hobbyists' aquariums but not species that were examined but did not pass the experimental stage. Of these, only five species succeeded in establishing populations, usually in local and limited areas. To minimize risks involved in the introduction of new species, Israeli policy makers must implement a clear course of action which balances the demand of local aquaculturists for new species with the need to protect the vulnerable freshwater ecosystem.
Three hydrilla (Hydrilla verticillata) biotypes are resistant to fluridone, the principal herbicide used in Florida. Be-cause of an anticipated demand for triploid grass carp (Ctenopharyngodon idella), a risk analysis was conducted to ex-amine the use of triploid grass carp to control hydrilla in large (>200 ha), open systems in Florida. An expert panel utilized the Generic Nonindigenous Aquatic Organisms Risk Analysis Review Process developed by the Aquatic Nuisance Species Task Force to assess five hydrilla management op-tions. Specifically, the panel assessed the risk of (1) eliminat-ing all vegetation for three years or more; or (2) vegetation coverage exceeding 50% for five consecutive years. Herbi-cide application, followed by stocking low levels of triploid grass carp and subsequent herbicide treatment, was consid-ered to be a lower risk option to achieve hydrilla manage-ment objectives. The expert panel emphasized the necessity of implementing well-supported system management and monitoring and determining stocking rates on a lake-by-lake basis.
Diploid and triploid hybrids with 48 and 72 chromosomes, respectively, occurred when female grass carp, Ctenopharyngodon idella, were artificially crossed with male bighead carp, Hypophthalmichthys nobilis. Diploid hybrids had a higher frequency of morphological abnormalities and were generally smaller than triploids. Lactate dehydrogenase and esterase isozymes of both parental species were expressed in the hybrids. LDH isozymes were encoded by three genetic loci, A, B and C. The C locus was active only in liver tissue. The C4 isozyme had a higher isoelectric point than the A4 or B4 isozymes.
The exotic grass carp ( Ctenopharyngodon idella ) has been used for almost a half a century in the United States as a bi- ological agent to control and manage aquatic plants. This long-lived generalist herbivore consumes large amounts of vegetation and can considerably alter habitat and impact aquatic communities. We conducted a literature review to determine whether previous studies adequately addressed ecological impacts of grass carp and their underlying mech- anisms. Our goal was to identify strengths and limitations of ecological assessment in the literature and suggest a trajec- tory of future research. The review yielded 1,924 citations on grass carp; however, data on ecological interactions were limited, and most research emphasized the biology of grass carp or eradication of aquatic plants rather than ecological mechanisms responsible for ecosystem-wide impacts. Very few studies addressed effects on habitat complexity or com- munity-structuring processes. We provide a comprehensive tabulated overview of feeding preferences and environmen- tal impacts of grass carp. We argue that ecology is para- mount to evaluating grass carp impacts and thorough understanding of these impacts is essential for the appro- priate management of aquatic communities. Current knowledge is not sufficient to accurately predict long-term effects of grass carp on freshwater ecosystems. We advise a more cautious approach to developing guidelines for grass
In Uzbekistan, female grass carp mature at age 3-4 years when they reach 54-67 cm in length. Absolute fecundity of 3-5 year old females was recorded to produce 100,000-1,000,000 eggs. The relative fecundity as 3-164 eggs per g of gutted fish. The gonadosomatic index of the mature females before ovulation was 9-20%. The diameter of ripe eggs in the gonads was 0.9-1.8 mm. Males mature at age 3 years when they reach 50-60 cm.
The herbivorous grass carp (Ctenopharyngodon idella V. and C.) is an important species for controlling nuisance aquatic vegetation. In the present study, chromosome-set manipulation and hormonal sex inversion were integrated to produce monosex females and males and sterile female triploids. The albino grass carp (AGC) served as a recessive genetic marker for induction of gyno-genesis and androgenesis. Sperm of common carp (Cyprinus carpio L.) or golden tench (Tinca tinca L.) were examined as activators of albino eggs for gynogenesis. Eggs of common carp and wild-type colored grass carp were tested for androgenesis of AGC. Early shocks (0.15-0.2t0) were applied to obtain the desired ploidy level in meiotic gynogenesis and triploidy and late shocks (1.6-2.2t0) in mitotic gynogenesis, androgenesis and tetraploidy. Pressure, heat, and cold shocks at several intensities were examined. Meiotic gynogenotes were obtained (200-600 individuals) in all experiments using UV-irradiated (800 J/m2) sperm of common carp. The highest survival of gynogenotes was obtained from eggs shocked by heat (40 ± 1 °C/2 min). In 1994, a group of fish was hormonally sex-inversed with androgen implants. Sex-inversed females (neomales) served as donors of X-bearing spermatozoa for the production of female monosex populations. The timing of late shock, required for induction of androgenesis and tetraploidy, was defined through induction of mitotic gynogenesis. Mitotic gynogenotes were produced by exposing activated AGC eggs to cold shock for different durations (10, 20 and 30 min). The survival and hatching of mitogynotes were inversely related to the duration of the shock. Androgenesis was induced in UV-treated eggs of common carp and wild-type colored grass carp, fertilized with intact AGC sperm. Only two diploid albino androgenetic fish survived more than one year. Female (XXX) triploids were produced by fertilizing AGC eggs with sperm of AGC neomales, then shocking them early to retain the second meiotic polar body. The use of neomales provided a mechanism for commercial-scale production of sterile (XXX) all-female AGC. So far, trials to induce tetraploid AGC using cold shocks have failed. Fluorocytometric examination was applied to assess the DNA contents in samples of ploidy-manipulated larvae and fish. Due to the highly applicative importance of tetraploid brood-stock, we intend to continue our study on tetraploidy.
Fingerling grass carp (Ctenopharyngodon idella), averaging 4.8 g (SD, 0.21), were stocked in 16 earthen ponds (0.04 hectare) at a rate of 11,875 fish/hectare and were fed a commercial crumbled trout feed for 41 d, followed by a floating catfish starter feed for 23 d. Subsequently, the fish were assigned to four feeding regimes (each treatment replicated in four ponds) and fed for 108 d. The treatments were (1) a commercial-type catfish floating feed fed twice daily; (2) a grass carp floating feed fed twice daily; (3) the grass carp floating feed fed once daily; and (4) the grass carp feed in a sinking pellet fed twice daily. The grass carp feed contained 15% dehydrated alfalfa meal (Medicago sativa). The catfish and grass carp feeds were designed to be similar in crude protein (35%) and estimated digestible energy (3.1 kcal!kg). During the 64-d conditioning period, when all fish were treated similarly, mean fish weight increased rapidly, from 4.8 to 68.4 g (SD, 4.2). During the 108-d experimental period, growth was slower, with a final average weight of 174.9 g (SD, 18.3). There was no significant (P > 0.05) treatment effect on fish size, but fish fed twice daily had a higher condition factor (K = 102[weight, g]/[length, cm]3) than those fed once daily. Feeding activity of the fish decreased when daytime water temperature exceeded 30°C in summer and again when the temperature dropped below 26°C in fall. These results indicate that grass carp will accept and utilize formulated feeds satisfactorily in growing from small fingerlings to a size capable of avoiding predation (175 g in weight and 24 cm in length).
Twenty-six morphological and meristic characters of diploid and triploid hybrids between female grass carp, Ctenopharyngodon idella and bighead carp Hypophthalmichthys nobilis were analyzed by discriminant-function analysis. Twelve characters were useful in distinguishing between diploids and triploids. When these 12 characters were subjected to discriminant-function analysis, 97% of the hybrids were correctly classified as either diploid or triploid. No single character allowed diploids to be distinguished from triploids. Triploid hybrids had fewer morphological abnormalities than did diploid hybrids, possibly because triploid hybrids had two sets of chromosomes from the same species.
Moribund golden shiners Notemigonus crysoleucas sampled during winter and spring and moribund grass carp Ctenopharyngodon idella sampled during summer were necropsied and cultured on cyprinid cell lines. In all cases, a syncytial cytopathic effect occurred and viruses were successfully passaged. Characterization by electron microscopy, diethyl ether resistance, iododeoxyuridine resistance, and acid resistance confirmed that the isolates were aquareoviruses. We used polymerase chain reaction to test all isolates; primer sets were based on a published sequence for segments 1, 2, 3, and 10 of the grass carp reovirus (GCRV). Products of the expected sizes were amplified, then cloned and sequenced. The isolates were about 97-100% identical to each other and to a published sequence for golden shiner virus (GSV) and were 90-93% identical to GCRV. At the amino acid level, our isolates were 96-100% identical to each other and to GCRV. The similarity among our isolates and the published GCRV sequence was equivalent to the similarity among published GCRV sequences; we therefore conclude that GSV and GCRV are the same virus. This conclusion is confirmed by our isolation of this virus from both moribund golden shiners and moribund grass carp. Based on our work, we conclude that GSV is synonymous with GCRV, and that GSV was probably imported into the USA concurrently with the introduction of grass carp by federal agencies in 1963.
The increasing numbers of otters (Lutralutra L.), which are protected by the CzechAct of Nature and Landscape Protection, arecausing serious problems for fishpondmanagement. The diet of otters on pond farmsconsists predominantly (80%) of common carp,Cyprinus carpio, and to a lesser extentother pond fish species (perch, Percafluviatilis, zander, Stizostedionlucioperca and grass carp, Ctenopharyngodon idella). The size of carpcaptured by otters ranged between 376–683 mmTL (500 88 mm) and 1,049–11,768 g(3,478 2,867 g). Reconstructed originalweight and length of captured grass carp andperch were 599 and 182 mm TL, and 2,665 and163 g, respectively. In most of prey fishcorpses left by otters, only viscera andassociated parts were consumed. The weight ofindividual common carp corpses was estimated as73.0 24.6 (26.3–95.9)% of theoriginal reconstructed weight, which means thatonly 27.0 17.2 (4.1–73.7)% of fishbody mass was consumed by otters. In perch,62.8% of fish body mass was left unconsumed.Heavy losses have been reported also on fishstocks in ice-covered ponds during the winterperiod, when shoals of resting fish have beendisturbed and stressed due to otter hunting.
The Asian fish tapeworm, Schyzocotyle acheilognathi (syn. Bothriocephalus acheilognathi) represents a threat to freshwater fish, mainly cyprinids, across the globe. This tapeworm possesses an extraordinary ability to adapt to different environmental conditions and, because of that, from its natural geographical origin in mainland Asia, it has colonized every continent except Antarctica. It is thought that this pathogenic tapeworm was first co-introduced into Mexico in 1965 from China, with the grass carp Ctenopharyngodon idella, although the first formal record of its presence was published in 1981. Over the past 35 years, the Asian fish tapeworm has invaded about 22% of the freshwater fish in Mexico. Because fish communities in Mexico are characterized by high species richness and levels of endemism, S. acheilognathi is considered as a co-introduced and co-invasive species. In this review, we update the geographic distribution and host spectrum of the Asian fish tapeworm in Mexico. Up until December 2016, the tapeworm had been recorded in 110 freshwater fish species (96 native and 14 introduced), included in 51 genera, 11 families and 4 orders; it was also widely distributed in all types of aquatic environments, and has been found in 214 localities. We present novel data from a survey aimed at establishing the distribution pattern of the tapeworm in native freshwater fishes of two rivers in north-central Mexico, and the genetic variation among individuals of this co-invasive species collected from different host species and localities. We discuss briefly the factors that have determined the remarkable invasive success of this parasite in freshwater systems in Mexico.
Grass carp, Ctenopharyngodon idellus, harbours complex intestinal bacterial communities, which are important in several physiological processes of their host. Intestinal microbiota of grass carp have been previously described in numerous studies. However, an overview on the bacterial community diversity, including their establishment, their functions in host's nutritional processes and immune-related responses, and use as probiotics, is absent. This study aimed to summarize the current understanding of the grass carp intestinal microbiota. In this review, we provide general information on the establishment and composition of intestinal microbial communities and factors influencing the diversity of gut microbiota. Also, this review covers the dietary effects of probiotics, prebiotics and/or synbiotics on the grass carp intestinal microbial communities and physiological characteristics. Although our knowledge of the grass carp intestinal microbiota is expanding rapidly, further studies on the factors affecting the diversity of intestinal microbes, interactions between intestinal microbiota and their hosts and application of probiotics/prebiotics/synbiotics in aquaculture industry, are needed.
Is concerned with the identity, distribution, feeding rates and growth of herbivorous freshwater fishes, as well as with the identity and nutritional quality of plants fed upon by these fishes. -from Author
This experiment was intended to identify the vitamin E (VE)-deficiency symptoms and to determine the requirement of grass carp Ctenopharyngodon idella for α-tocopherol. For this purpose grass carp fingerlings weighing 4.5g on average were fed diets with various levels of α-tocopherol. Fish fed an α-tocopherol deficient diet showed the so-called 'sekoke disease', a similar symptom to the apparent muscular dystrophy of carp, characterized by a marked loss of flesh in the back, while also revealing high moisture and low protein contents in muscles, and the reduction of α-tocopherol content in hepatopancreas and muscle. Lordsis was also observed in fish fed the α-tocopherol deficient diet. Symptoms such as the apparent muscular dystrophy with or without lordsis started appearing from the 9th week of feeding (the 16th week from the pre-feeding experi-ment). Even though fish fed 5 and 10mg of α-tocopherol showed good growth and feed ef-ficienecy, high incidences of the apparent muscular dystrophy and lordsis were also noted. Taking into consideration the incidence of the apparent muscular dystrophy and lordsis as well as the tissue levels of α-tocopherol, it is suggested that the requirement of grass carp fingerlings for α-tocopherol is about 20mg per 100g diet.
Part 1 deals with the Principles of aquaculture, including 15 Chapters (Basis of aquaculture, History of aquaculture and present state, National planning of aquaculture, Selection of sites, Selection of species, Design and construction of aquafarms, Nutrition and feeds, Reproduction and genetic selection, Health and diseases, Control of weeds, pests and predators, Economic and finacing of aquaculture, and farm management;
Part 2 deals with Aquaculture practices, including chapters on Carps, Trouts and salmons, Catfishes, Eels, Tilapias, Grey mullets and milkfish, Yellowtail, Sea-basses and sea-breams, Other finfishes, Shrimps and prawns, Crayfishes and crabs, Oysters and mussels, Clams, scallops and abalones, Integration of aquaculture with crop and livestock farming and Stocking of open waters and ranching.
Genetic improvement efforts in Israel have focused mainly on common carp (Cyprinus carpio) and tilapias and, only recently, on marine fish species. Genetic improvement of tilapias has focused on the all-male inter-specific hybrid Nile tilapia (Oreochromis niloticus) × Jordan tilapia (O. aureus). Since realized heritability for growth rate in the gilthead sea bream (Sparus aurata) was estimated to be 0.45, a mass selection program was initiated. Some efforts are being devoted to testing the benefits of crossbreeding and inter-specific hybridization with Diplodus sargus and red sea bream (Pagrus major). Genetic engineering efforts are currently directed mainly towards developing methods of producing transgenic carp and gilthead sea bream carrying exogenous GH genes. -from Author
Feeding intensities (number of bites per minute) were recorded each hour over a 24-h diel cycle for young grass carp fed three diets. The grass carp did not show distinct meals. Grass carp receiving plant diets (duckweed or elodea) fed almost continuously throughout the 24 h, while fish fed the animal diet (tubificids) ceased feeding or had very low feeding intensities for about a quarter of the diel cycle. The average feeding intensity in fish fed duckweed was three times higher than that in fish fed elodea and tubificids. Average dry matter intake per bite was much higher in fish fed the animal diet than in those fed the plant diets. In most individuals, there was no significant difference in feeding intensity between daytime and nighttime.
An electrophoretic survey was conducted to estimate the amount of genetic variation that was detectable in proteins of grass carp stocks being artifically propagated in the United States. Staining procedures for nonspecific protein and 18 specific enzymes revealed an estimated 49 loci among the five tissues that were examined. The three polymorphic loci identified included the enzymes phosphoglucose isomerase (PGI) and esterase (Est), and the serum protein haptoglobin (Hp). The somewhat low average heterozygosity per locus (0.021) was partially attributed to the fact that four of the five stocks examined were derived from progeny of a single mating. This small common gene pool indicates that these stocks are inbred relative to wild populations and are therefore probably less capable of adapting to suboptimal spawning conditions. The intentional breeding of different homozygous combinations of variant alleles in hatchery stocks is recommended as an effective means of monitoring the spread and the relative contributions of these stocks.
In the Ivory Coast, grass carp (Ctenopharyngodon idella) have been integrated in the tilapia-based polyculture in order to increase pond productivity. In the tropical conditions prevailing there, female cycles seemed disrupted. We describe oogenesis in these conditions using histological observations, monitoring of individual cycles with intraovarian biopsies, endocrinal monitoring (development of a specific enzyme-linked immunosorbent assay (ELISA) for vitellogenin (Vg), measurement of plasma oestradiol-17β (E2) and testosterone (T)) and comparison with grass carp raised in Poland. We noted that oogenesis was blocked in all females at the migrating germinal vesicle stage, precluding ovulation or spawning without artificial induction. High rates of atypical post-vitellogenic oocytes (translucent, not filled with yolk granules) were observed in many females. Female individual cycles also displayed atypical features: cycles were sometimes (10% of females) blocked at the beginning of vitellogenesis (BV), for females displaying abnormally low E2 (0.5 ng/ml) and Vg (30 μg/ml) levels compared to “normal” females (1.4 ng/ml and 223 μg/ml, respectively). The duration of the cycles was highly variable among females (a few days to several weeks). Sexual cycles were unsynchronised (all the ovarian stages could be found for all seasons) and the number of females at the end of vitellogenesis (EV) was low (
An automated system for egg collection, hatching, and transfer of larvae of several cultured freshwater finfish has been developed. The system consists of a spawning tank, a filter, an incubation tank, hatching nets, and larviculture ponds. Using this system, grass carp (Ctenopharyngodon idellus), bighead carp (Aristichtys nobilis), silver perch (Bidyanus bidyanus), palmetto bass (Morone saxatilis×M. chrysops) and black carp (Mylopharyngodon piceus) were successfully induced to spawn with a single hormone injection (LHRH-a at 15 μg/kg for grass carp and bighead carp; HCG at 200, 400 and 600 IU/kg for silver perch, palmetto bass and black carp, respectively). Using this system, fertilized eggs flowed freely into nets for normal hatching, and the hatched larvae were conveyed automatically into larviculture ponds. The new automated system reduces labor. It achieved relatively high rates of spawning, fertilization and hatching. The filtration and reuse of culture water conserves water. This system offers an improvement to the existing finfish hatchery technology.
The structure of the BIOCAT database, which contains records of the introductions of insect natural enemies for the control of insect pests worldwide, and is now available online, is explained. It is a useful summary of biological control effort and a guide to factors which may influence the success of introduction programmes, but is not detailed enough for making firm predictions.
The study was aimed at determining the optimal level of protein in a casein diet for grass carp. There was a linear relationship between the percentage of protein in the diet and the increase in fish protein and weight up to optimal levels of 41 and 43%, respectively. No further increase in fish protein or weight was noted with diets containing up to 64% of protein. However, if the optimal level was defined by the parabolic curve with the formula y = 36.21 + 6.238x − 0.0593x2, it would equal 52.6 ± 1.93%. Net protein utilization (NPU) values for experimental diets were obtained using a formula which took the maintenance nitrogen metabolism on a non-protein diet into consideration. This NPU formula was related to the length of the experiment, difference in the weight of fish at the beginning of the experiment, and growth of fish fed protein diets. Both protein efficiency ratio (PER) and NPU decreased with the increase in protein content of the diets according to the formulae y = 1.966−0.018x and , respectively.
Twoyear classes of grass carp and F, hybrids resulting from bighead carp male x grass carp female were compared at various stocking densitiesforaquatic plant control. One and two year old grass carp exhibited higher survivalrates and better growth rates than the same age hybrid grass carp. The presence of grass carp or hybrid grass carp decreased both Secchi disc transparencies and dissolved oxygen values. Grass carp had a greater negative effect upon these measurements because they removedthe vegeta- tion quicker than the hybrid grass carp. These apparent detrimentaleffects on water quality are necessary trade-offs for vegetation removal by any method. Grass carp and hybrid grass carp utilized Charasp., Potamogeton pectinatus, Hydrodicton sp., Rhizocloniasp., and Pithophora sp. Two year old hybrid grass carp required approximately twice as much time as the same age grass carp to eliminate dense growths of the vegetation listed above. One year old hybrid grass carp were slightly less effective than one year old grass carp at controlling these same plant species. However, it was extremely difficultfor one or two year old hybrid grass carp to total- ly eliminate dense growths of these plant species except at high stocking densities. Theuse of mean vegetation heights to indirectly measure totalplant biomass was unacceptable whenever unpreferred floating plant species were present. The hybrid grass carp appeared to be a poor alternative biological control for nuisanceaquatic vegetation whencompared directly to the grass carp.
Thirty feeding trials were conducted using triploid grass carp (Ctenopharyngodon idella Val.) fed hydrilla (Hydrilla verticillata Royle) to establish feeding and growth rates as a function of fish size and water temperature. Size of fish ranged from 0.2 to 9.1 kg and water temperatures ranged from 17 to 27 C. Feeding trials consisted of fish and hydrilla housed in 4 m wire mesh cages suspended at weekly intervals in an experimental pond. Utilizing pre- and post-weights of fish and hydrilla, weight gain, relative and absolute feeding rates, and feeding efficiency were found to increase with increasing water temperatures. Relative and absolute feeding rates for 0.2—0.4 kg fish at 17 C were approximately 25% of that for similar sized fish at 27 C. Above 25 C, these small fish consumed their body weight per day of hydrilla. While relative feeding rates (gm hydrilla/gm fish/day) declined with increase in fish size (at constant temperature), this was not the pattern for absolute feeding rates (gm hydrilla/fish/day) where consumption rates ranged from 750 to 1200 gm hydrilla/day for fish weighing more than 1 kg.
Young grass carp held under laboratory conditions were fed either duckweed or tubificid worms. Food consumption (C), faecal production (F), excretion (U), metabolism (R) and growth (G) were estimated for fish fed both diets. Fish fed tubificid worms had higher growth rates than those fed duckweed, in terms of wet weight, dry matter, protein, lipid and energy. Fish fed duckweed consumed more wet and dry matter than did the fish fed tubificids, but rates of protein and lipid consumption were lower. The energy budget was estimated to be 100C = 9F+ 8U+ 61R+ 22G for fish fed tubificids, and 100C = 35F+ 5U+ 51R+ 9G for fish fed duckweed. Linear relationships existed between specific growth rate in wet weight and rate of food absorption (consumption minus faecal production) in dry matter, protein or energy. Food type did not have a significant effect on these relationships. It was concluded that differences in growth rate between grass carp fed different diets were mainly caused by differences in absorption rate.
Ovulation was stimulated in females of grass carp Ctenopharyngodon idella (Valenciennes) and silver carp Hypophthalmichthys molitrix (Valenciennes) using LHRH-a with pimozide at doses of 15 μg kg− 1 and 5 mg kg− 1 body weight respectively. The results of reproduction after the LHRH-a stimulation were compared with the results of spawning recorded in the case of hypophysation. In the case of grass carp treated with LHRH-a, the percentage of stripped females was higher than that recorded after hypophysation, while the female of silver carp yielded eggs irrespective of the type of applied ovulation stimulator. The average weight of eggs (in grams and as a percentage of female body weight) obtained from both grass carp and silver carp did not differ significantly in the groups treated with LHRH-a and carp pituitary. Average percentages of fertilization and of live embryos did not differ significantly in the groups treated with the two ovulation stimulators. This statement concerns the two species investigated. Statistically significant differences (P≤ 0.05) were calculated with respect to the mean percentage of deformed larvae. This percentage was distinctly higher after an LHRH-a treatment in both grass carp and silver carp. Irrespective of the applied ovulation stimulator, a greater weight of eggs of better quality was obtained from silver carp females.
Electrophoretic analysis of six types of tissue (serum, erythrocyte, liver, kidney, muscle and eye) and seven different isoenzymes (LDH, MDH, Est, ADH, IDH, α-GPDH and SOD) from both healthy grass carp, Ctenopharyngodon idellus Cuvier & Valenciennes, and carp affected by haemorrhagic disease was performed. It was found that: (1) Enzymes from diseased grass carp showed the most drastic changes within each tissue. The absolute activity of LDH in serum from the diseased fish increased to approximately twice that of the healthy fish; whereas the relative activity of A4 and A3B1, the main components of A sub-base in both serum and erythrocytes, was accelerated. (2) The isoenzymic changes in the control groups, diseased fish, artificially infected fish and healthy fish from diseased ponds indicated that biochemical changes occurred in the tissues before pathological change.
Comparative karyological studies on Chinese carps (Ctenopharyngodon idella, Aristichthys nobilis, Hypophthalmichthys molitrix) were carried out to determine the possiblities of hybridization. The diploid chromosome number, the morphological distribution of chromosomes, the arm ratio, the total and relative lengths of chromosomes, the total length of chromosome sets, and the number of arms were determined. Cross-breeding of grass carp and bighead was tested, and resulted in viable progeny. Karyological analyses of the F1 hybrid generation were made. The hybrid proved to be triploid.
Young grass carp (12–13 g) were kept at five ration levels ranging from starvation to ad libitum feeding at 30°C. They were fed duckweed. Food consumption, absorption efficiency and growth were determined directly, and metabolism and nitrogenous excretion calculated indirectly from energy and nitrogen budgets, respectively. The relationship between specific growth rate and ration size was linear. Absorption efficiency for energy was not affected by ration size and averaged 50.6±0.57% (mean±s.e.). Depending on ration size, energy lost in excretion accounted for 4.5–5.9% of the food energy, energy channelled to metabolism accounted for 34.4–48.3% of the food energy, and energy retained as growth accounted for 6.7–11.9% of the food energy. Regardless of ration, a constant proportion of food energy (30.7%) was accounted for by feeding metabolism (total metabolism minus fasting metabolism). The energy budget at the maximum ration was: 100C=49.1F+4.5U+3.6Rfa+30.9Rfe+11.9G, where C, F, U, Rfa, Rfe and G represent food consumption, faecal production, excretion, fasting metabolism, feeding metabolism and growth, respectively.
The Linpe method of induced ovulations and/or spawning of cultured fish consists of treatment with an analogue of gonadotropin-releasing hormone (GnRH) plus a dopamine antagonist. Initial experiments on common carp, silver carp, mud carp, bream, grass carp, bighead carp, black carp and loach confirm that ovulation can be induced in each of these species by injection of pimozide or domperidone plus [D-Ala6, Pro9 NEt]-luteinizing hormone-releasing hormone (LHRH-A) or [D-Arg6, Trp7, Leu8, Pro9 NEt-]-LHRH (sGnRH-A). Domperidone and sGnRH-A are preferred because of higher potencies in several species, allowing for their use at low dosages. For most species one set of simultaneous injections of the two drugs has proven sufficient to induce a high rate of ovulation within a predictable period of time. Ovulations are complete and ovulated eggs have been shown to be fertile. Hatching rates and fry survival are as high as high as with traditional methods of induced spawning. Subsequent reproductive cycles appear not to be altered by induced ovulation with the Linpe method. Although some refinement of dosages of drugs is required, the Linpe method has proven to be a highly successful procedure for induced ovulation and/or spawning of cultured freshwater fish in China.
High percentage triploidy was induced by means of hydrostatic pressure and heat shock treatments of fertilized grass carp eggs. Estimates of triploidy exceeded 98% in 9 of 10 treatments involving hydrostatic pressures of 7000 or 8000 PSI for a duration of 1 or 2 min, applied 4 min after egg-sperm activation. Estimated hatch relative to the controls averaged 69.1%, ranging from 21.9 to 100%. The best heat shock parameters were 42°C for a duration of 1 min starting 4 min after egg-sperm activation resulting in an average of 66.7% (0-est. 100%) triploidy. Percent hatch relative to the controls averaged 72.5%, ranging from 43.9 to 100%. Delaying fertilization of ovulated grass carp eggs for up to 30 min did not have a negative effect on triploid conversion or survival compared to controls.
Grass carp (Ctenopharyngodonidella Val.) stocked at a low density (29 kg ha−1) to one of two small ponds significantly reduced the biomass of aquatic macrophytes (especially of the filamentous alga Cladophoraglobulina Kütz.) and changed the species composition of the higher aquatic plant community. After grass carp stocking (in 1999), Myriophyllumspicatum L., Ceratophyllumdemersum L. and Lemnaceae species replaced the species present originally: Eleocharisacicularis (L.) Roem. et Schult., Potamogetonpusillus L. and P.pectinatus L., which were dominant in 1998.
Fingerling and juvenile grass carp (Ctenopharyngodon idella) were fed elodea (Elodea densa), coontail (Ceratophyllum demersum), eurasian water milfoil (Myriophyllum sp.) or a commercial catfish feed at 26°C or 20°C, respectively. Diet significantly affected consumption, digestion, growth and muscular fatty acid composition of grass carp. Fingerling grass carp fed Elodea at 26°C consumed a ration (wet weight) higher than their body weight, with a digestion efficiency around 50%, and achieved excellent growth. Fish fed other diets in this study grew more slowly and the growth rates were positively related to the daily intake of protein. Grass carp readily elongated and desaturated dietary linolenic acid into long chain polyunsaturated fatty acids. Dorsal muscle lipids from fish fed Elodea at 26°C contained 35% n−3 fatty acids and the n−3 fatty acid content in Elodea-fed fish was 7- or 4-fold more than in those fed catfish feed at 26°C or 20°C, respectively. Among the plant-fed fish, muscle docosahexaenoic (22:6n−3) levels were very similar at 26°C while linolenic and eicosapentaenoic (20:5n−3) acid levels varied. Grass carp selectively deposited dietary n−6 fatty acids in their muscle. Total n−6 fatty acid levels in all groups of fish were very similar at 26°C or 20°C regardless of the great differences in linoleic level among the experimental diets. The ratio of saturates to unsaturates in grass carp muscle fell in a narrow range (0.31–0.36) irrespective of large differences in this ratio among the diets (0.27–0.66).
Edible fish stocked in rice fields at a density of 600-800 fry per mu (1 mu = 1/15 hectare) for 150-170 days may act as an effective mosquito biocontrol agent. Common carp (Cyprinus carpio), grass carp Ctenopharyngodon idella) and Tilopia spp. killed late stage larvae and pupae of Anopheles sinensis and Culex tritaeniorrhyncus in laboratory and field trials. Stocking of fish in experimental rice fields decreased larval numbers significantly in comparison with control areas. Expansion of fish stocking in rice fields on a large scale over several years correlated with a marked decrease in malaria transmission. The addition of fish to the rice fields also resulted in increased yields. A ditch-ridge system of field arrangements is described for optimization of fish handling. Preliminary cost-benefit analysis indicates that this approach to mosquito control conveys considerable economic advantage and thus provides incentive to the community to participate in vector control programs. Farmers' experience in Guangxi over a number of years indicates that the use of edible fish for this purpose can be carried on a large, commercially viable scale.