Carp Densities Research Articles

Effects of Stocking Density of Filter-Feeding Fishes on Water Quality and Bacterial Community in Rice–Crayfish Polyculture System

To evaluate the effects of filter-feeding fishes on water quality and bacterial community in the rice–crayfish coculture system, four different stocking densities of bighead carp (0, 500, 1000, 1500 ind./200 m2) were set up in rice–crayfish coculture systems. Water samples in the systems were collected biweekly to detect dissolved oxygen (DO), temperature (T), potential of Hydrogen (pH), ammonia nitrogen (NH4+-N), nitrite nitrogen (NO2−-N), nitrate nitrogen (NO3−-N), total nitrogen (TN), total phosphorus (TP), and Chlorophyll-a (Chl-a); the bacterial community in the water was analyzed simultaneously, then the correlation between water quality and microorganisms were studied. The results showed that concentrations of TN, TP, NO2−-N, and NH4+-N decreased while DO and NO3−-N increased along with the breeding process. NO2−-N, NO3−-N, TN, and NH4+-N were important environmental factors affecting the bacterial community structure in water (p < 0.05). Bighead carp stocking had an impact on the diversity, richness, and evenness of the bacterial communities in the systems. The dominant bacteria in the four different carp density groups were Proteobacteria, Actinomycetes, Bacteroidetes, and Cyanobacteria. Bighead carp increased the abundance of Bacteroidea but reduced that of Actinomycetes, Cyanobacteria, and Proteobacteria. The introduction of bighead carp promoted the conversion of nitrogen and phosphorus, reducing the risk of cyanobacterial blooms. Group 1000 ind./200 m2 exhibited the best effect on the removal of nitrogen and phosphorus from the water body.

EVALUATION OF DIFFERENT STOCKING DENSITY OF SMALL INDIGENOUS FISH PABDA WITH CARP POLYCULTURE SYSTEM

An experiment on the polyculture of carps with high valued small indigenous fish species (SIS) Pabda (Ompok pabda) was carried out for 152 days to evaluate the production performances of carp and pabda in some on-farm pond conditions in three Upazila of Jhenaidah district. Three stocking densities of Pabda were T1500, T2600, and T3-700 fish per decimal where released, carp density was the same among the treatments at 246 nos/33 decimal. Fish was fed with commercial (sprectahexa, mega) pelleted feed at the same rate at the different stages of Pabda (0.66-50 gm BW @ 20%-4% twice a day respectively). The weight gain of Pabda was 40.965 ± 0.04, 35.17± 0.11 and 30.99 ± 1.17 g in T1, T2, and T3 treatments, respectively. The production levels showed significant difference (P<0.05) among the treatments. The SGR (%) of Pabda was 2.76 ± 0.0006, 2.66 ± 0.002 and 2.58 ± 0.024 in T1, T2, and T3, respectively that showed a significant difference (P<0.05) among the treatments. The weight gain of carp was 1177.24 ± 30.87, 1150± 0.001, 1154.85 ± 3.43 in T1, T2, and T3, respectively, which was also significantly different (P<0.05) when ANOVA was performed. The water quality parameters like transparency and dissolved oxygen in the treatments showed significant differences (P<0.05) except temperature, pH, and ammonia nitrogen. The results of the present study demonstrated that the fishes showed better growth, survival, and production in the low stocking density of Pabda in T1 treatment.

Technological parameters of carp growing (Cyprinus carpio) at different stocking densities

This article presents a study of the technology of growing carp (Cyprinus carpio) using different stocking densities in feeding ponds. Carp is one of the most common and essential freshwater fish species for commercial farming and consumption. The study was conducted over several months, with an assessment of carp's growth, survival, and productivity when using different stocking densities in feeding ponds. Different stocking densities included low (sparse), medium, and high (dense) carp individuals per unit area. To experiment, four groups of carp individuals were kept in feeding ponds at different stocking densities from 2,000 to 3,500 specimens per hectare of water area. Using extensive planting material of carp with an average weight of 55 g makes it possible to obtain commercial carp with an average weight of 485 g to 650 g during a two-year cycle of cultivation in the conditions of the second fish farming zone without reducing fish production. At the same time, the largest concentration of carp was obtained in a pond with sparse planting of annuals – 2.0 thousand specimens/ha. An increase in the planting density of yearlings of carp to 3.5 thousand units/ha led to a decrease in the average daily weight of two-year-old carp to 510 g while maintaining a high fish production of 1122 kg/ha. At the same time, a hydrochemical analysis was carried out in the ponds, and the amount and biomass of the natural feed base (phyto-, zooplankton, and zoobenthos) were determined. The analysis of the research results indicates that the stocking density of carp has a significant impact on its productivity. The sparse stocking conditions promoted more significant growth and better development of the fish, which may be due to less competition for food and space. On the other hand, high stocking density led to a slight decrease in growth and did not affect survival and fish productivity. The results of this study have practical applications for fish farms engaged in the cultivation of carp. They emphasize the importance of an optimal balance between the number of fish, the availability of natural feed, and the area of the feeding ponds in order to achieve maximum growth and productivity with minimum costs of keeping and feeding the fish. Such research will help improve fish farming technologies and optimize production processes to ensure sustainable and efficient development of the industry.

Effects of fentin acetate molluscicide on biological performance and haematological of the common carp, Cyprinus carpio cultivated at rice field water

Molluscicide of fentin acetate (C20H18O2Sn) is commonly used at the present due to effective in terms to control of molluscs in the rice field. The aims of this experiment is to determine toxicity effect of fentin acetate on growth, productivity, and blood glucose on the common carp, Cyprinus carpio cultured at rice field water. A 12 of rice field plots with size of 25m2 each were used. The stocking density of common carp was 25 fish/m2 for each rice plot. The culture period of the common carp was 21 days. The different fentin acetate concentration as treatments were as followed M0) without molluscicide; M1) 0.375 g/L of molluscicide; M2) 0.75 g/L of molluscicide); and M3) 1.5 g/L of molluscicide. Statistical analysis using one-way ANOVA with three replicates for each treatment was performed. The result showed that the treatment of molluscicide at 0.75 g/L was significantly different to the others on survival rate and productivity (p<0.05). Application of 0.75 g/L of molluscicide showed a positive correlation on blood glucose value.

Growth performance of different fish species during dry period in Chitwan, Nepal

In order to assess the growth and yield of different fish species during dry period, an experiment was conducted in the Aquaculture Farm of Agriculture and Forestry University, Rampur, Chitwan from 1 April to 10 July, 2021. The experiment included three treatments: T1 (Carp polyculture), T2 (Common carp Cyprinus carpio monoculture) and T3 (Nile tilapia Oreochromis niloticus monoculture), each with three replications. Silver carp (Hypophthalmichthys molitrix 7%), Bighead carp (Aristichthys nobilis 20%), Grass carp (Ctenopharyngodon idella 13%), Rohu (Labeo rohita 30%), Mrigal (Cirrhinus mrigala 10%) and Common carp (20%) were stocked at densities of 1,400, 4,000, 2,600, 4,000, 6,000 and 2,000 fish/ha, respectively. Stocking density of Common carp and Nile tilapia was 20,000 fish/ha. Fish were fed with sinking pellet (28% crude protein) at the rate of 3% of body weight. Gross and net fish yield was significantly higher in T3 (89.89±0.67 t/ha/yr,16±0.25 t/ha/ yr) than in T2 (4.88±0.38 t/ha/yr, 4.05±0.35 t/ha/yr) due to higher (p&lt;0.05) survival in T3 (72.5±11.3 %) than in T2 (40.6±4.5 %). Gross margin was significantly higher in T3 (1,257,482±186,600 NRs./ha/yr) than in T2 (434,250±124,753 NRs./ha/yr). Based on higher survival, yield and gross margin, Nile tilapia monoculture is suitable for dry season.

Validation of a Portable eDNA Detection Kit for Invasive Carps

Loop-mediated isothermal amplification (LAMP) is a rapid molecular detection technique that has been used as a diagnostic tool for detecting human and animal pathogens for over 20 years and is promising for detecting environmental DNA shed by invasive species. We designed a LAMP assay to detect the invasive carps, silver carp (Hypophthalmichthys molitrix), bighead carp (Hypophthalmichthys nobilis), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella). To determine the sensitivity of the LAMP assay, we determined limit of detection (LOD) for each invasive carp species and compared with the performance of a grass carp quantitative PCR (qPCR) assay in LOD and in a mesocosm study. We used two grass carp densities, 3 juvenile grass carp in one mesocosm and 33 juvenile grass carp in the other. Prior to adding grass carp to the mesocosms, we added 68 kg of fathead minnows (Pimephales promelas) to each mesocosm to simulate farm ponds used for raising bait fish. We filtered 500 mL of water per sample to compare LAMP and qPCR analysis, and we collected 50 mL grab samples that were only analyzed using qPCR to gain additional data using a higher-throughput method to monitor environmental DNA (eDNA) levels throughout the study period. No eDNA for any of the four invasive carp species was detected in water collected from the mesocosms during the three days prior to adding grass carp. Forty-eight hours after grass carp addition to mesocosms, we detected grass carp eDNA in the mesocosm containing 33 grass carp using the LAMP assay. However, we failed to detect any grass carp DNA in the mesocosm containing 3 grass carp with the LAMP assay throughout the study. We analyzed the data using an occupancy model and found that the 500 mL filter samples yielded a higher eDNA capture probability than 50 mL grab samples in the mesocosm containing three grass carp but had similar eDNA capture probability in the mesocosm containing 33 grass carp. Both LAMP and qPCR reliably detected grass carp eDNA 2 days after grass carp addition, but detections were more consistent with qPCR. The LAMP assay may have utility for certain niche uses because it can be used to rapidly analyze eDNA samples and is robust to inhibition, despite having some limitations.

Benthivorous fish cause a shift from a clear water state established by combining​ phosphorus immobilization and submerged macrophytes to a turbid state: A mesocosm study

Both chemical phosphorus (P) immobilization and submerged macrophytes are widely used in lake restorations to reduce internal phosphorus loading. Their combined effects seem much stronger than used alone. However, benthivorous fish populations recover fast and they may thus counteract the restoration effects. We conducted a mesocosm experiment with three densities of crucian carp ( Carassius auratus gibelio ) to study the effects of benthivorous fish on the combined effects of lanthanum (La) modified bentonite and submerged macrophyte Vallisneria denseserrulata in lake restoration: control (fish-free), low-density (45 g m −2 ) and high-density (83 g m −2 ). Crucian carp increased the concentrations of total phosphorus, total nitrogen, total suspended solids, and chlorophyll a and deteriorated the light climate in the water column compared with the controls. The porewater soluble reactive phosphorus concentrations in the deep sediment were two times higher in the high-density treatment than in the control group and the low-density treatment. Crucian carp increased the mobile phosphorus (mainly the NaOH-OP) in the 0–2 cm sediment, likely due to the dilution of La in the surface sediment as caused by accelerated downward transportation of La, and at the same time La-bound P (part of the HCl-P fraction) was mixed deeper into the sediment with increasing fish density. In the high-density mesocosms, plant biomass and density were reduced by 37% and 51%, respectively, which is another possible mechanism for the water quality deterioration. We conclude that it is important to control benthivorous fish when conducting lake restoration by combining phosphorus immobilization and submerged macrophytes. • Benthivorous fish dampened the combined effects of Phoslock® and macrophytes. • High-density benthivorous fish increased porewater SRP concentrations. • Benthivorous fish increased the mobile P (mainly NaOH-OP) in the surface sediment. • Benthivorous fish hampered the growth of submerged macrophytes.

Biocontrol of Oreochromis mossambicus Population by Chitala chitala (Hamilton, 1822) in a Composite Carp Culture System of Purulia District in West Bengal, India

Aims: Pond-based carp production in the Purulia district in West Bengal, India is confronted with several challenges. This study aimed to establish an alternative semi-intensive carp production method for the district by addressing an endemic challenge i.e. recruitment of O. mossambicus, through an endangered (EN) and native predatory fish, Chitala chitala.&#x0D; Study Design: Present study has been conducted on two numbers of perennial water resources with 1 ha effective area; where annual production of Indian Major Carps (IMC) and impact of O. mossambicus and C. chitala on the same culture system have been compared.&#x0D; Place and Duration of Study: This study was conducted in farm conditions from 2018 to 2020, in two freshwater earthen ponds, Gosai Bundh (N23.47737/E86.79032) and Bara Notun Bundh (N23°46439/E86°65080), at Uluberia village under Kashipur Block of Purulia district in West Bengal, India.&#x0D; Methodology: Stocking density of Indian Major Carp (IMC) fingerlings was maintained at 8000 numbers (4:3:3 ratio of catla : rohu : mrigala) per ha (T1). After getting contaminated by O. mossambicus, wild C. chitala juveniles have been introduced in the similar facility (T2). Results of T1 and T2 were compared with control pond (C) containing IMC only. Recruitment of O. mossambicus and growth performance of C. chitala and IMCs determined periodically and annually.&#x0D; Results: Increasing growth of C. chitala showed contrasting impact over O. mossambicus fry recruitment. Survival percentage of C. chitala remains high in T2. While, poorest growth performance of IMCs have been observed in T1. Among IMC’s C. catla showed best survivality in every experimental ponds.&#x0D; Conclusion: Excessive recruitment of the O. mossambicus population can be controlled by C. chitala in a pond-based IMC culture system.

Experimental observation on the effects of bighead carp (Hypophthalmichthys nobilis) on the plankton and water quality in ponds.

It is a common practice to improve the water environment of rivers and lakes in China by the enhancement and releasing (EAR) of silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) for biomanipulation. However, the quantity of bighead carp and its effect on water quality and plankton community have been the focus of debate among ecologists. Herein, in order to more accurately simulate the environmental conditions of lakes, we selected earthen ponds with large areas adjacent to Lake Qiandao from May to August in 2016 to study the responses of water quality condition and plankton community to a gradient of bighead carp stocked alone. Experimental groups with different densities of carp stocked were set as follows: 12.1 (LF), 23.5 (MF), and 32.5 g/m3 (HF), and a control group with no fish (NF). Results showed that total phosphorus (TP) in the fish-containing groups considerably decreased, and the lowest chlorophyll-a concentration (chl-a) was detected in the MF group. The biomass accumulation of the crustacean zooplankton was suppressed after carp was introduced, but the diversity, richness, and evenness of the crustacean zooplankton were weakly affected, except in the HF group. Phytoplankton biomass especially that of cyanobacteria was grazed rapidly by fish in the MF and HF groups and biodiversity indices were considerably increased in the fish-containing groups, especially in the late stages of the experiment. At a fish stocking density of 23.5-38.8 g/m3, the highest efficiency in controlling cyanobacteria and promoting water condition was achieved, and the impact on zooplankton diversity was weak. Our results indicated that bighead carp can be included in the EAR of lakes and reservoirs, but the optimal density of bighead carp stocking should be carefully considered.

Hyperstability in Electrofishing Catch Rates of Common Carp and Bigmouth Buffalo

AbstractElectrofishing catch per unit effort (CPUE) can be an effective index of relative abundance when CPUE is proportional to population density. However, the relationship between fish catch rates and density can be variable and not proportional because catchability may not be constant under a range of environmental conditions. Hyperstability occurs when catch rates change faster than population density, whereas hyperdepletion occurs when catch rates change slower than population density. We used capture–mark–recapture methods to estimate density of Common Carp Cyprinus carpio and Bigmouth Buffalo Ictiobus cyprinellus across 24 lake‐years. Next, we developed log‐linear mixed‐effects models to assess the relationship between catch rates and density to predict electrofishing CPUE based on density and environmental covariates. Common Carp and Bigmouth Buffalo electrofishing CPUE exhibited hyperstability; CPUE initially increased faster at low density but reached an asymptote as density continued to increase. Common Carp catch rates increased with water temperature and were negatively associated with season; highest catch rates occurred in the warmest temperatures of spring, whereas the lowest catch rates occurred in the coldest temperatures of fall. Bigmouth Buffalo electrofishing CPUE was negatively related to water temperature but had a quadratic relationship with season; catch rates were highest in the spring and fall when water temperatures were coldest. Secchi depth, shoreline length, and maximum depth did not influence our model predictions in either species. Electrofishing had little power to detect simulated changes in Bigmouth Buffalo density regardless of sampling effort, whereas power to detect changes in Common Carp density increase with population changes and sampling effort. At low population densities for both species, electrofishing CPUE is expected to increase or decrease faster than density and can obscure conclusions about population trajectories but may still be useful for monitoring population fluctuations if hyperstability is accounted for by a correction factor.

An in-pond tank culture system for high-intensive fish production: Effect of stocking density on growth of grass carp (Ctenopharyngodon idella Valenciennes, 1844) and blunt snout bream(Megalobrama amblycephala Yih, 1955)

Pond partitioned aquaculture system is developed in recent years, and it contributes to increasing yield and lowering land occupation. Based on the concept of partitioned aquaculture system, a new in-pond tank culture system (IPTCS) was constructed in this study. This system consists of culture tank, capture and aeration module, waste collection module, and vertical flow constructed wetland (VFCW), and the effective rearing area takes up about 10.05% of the pond area. In IPTCS, grass carp ( Ctenopharyngodon idella Valenciennes, 1844) and blunt snout bream ( Megalobrama amblycephala Yih, 1955) were reared at high and low stocking densities for 120 days. The initial density of grass carp in the high and low density groups was 15 kg m −3 and 7.5 kg m −3 , respectively, and that of blunt snout bream were 10 kg m −3 and 5 kg m −3 . During the experiment, the aeration module worked 6 h / day, and the waste collection module worked 5 min / day. The results showed that high stocking density had a negative impact on the growth performance and muscle quality of grass carp and blunt snout bream, and that the water quality in the culture tank gradually was deteriorated with the increasing stocking density. The economic benefits of different stocking densities in this system were investigated in this study, and grass carp high-density rearing failed to generate high benefits, but blunt snout bream high-density rearing leads to a higher income. The feasibility and rearing effect of the in-pond culture tank system were preliminarily confirmed. • A new type of in-pond tank culture system (IPTCS) was constructed. • The economic benefit of theIPTCS was analyzed.

Study of the growth of common carp CYprinus carpio L. 1758 In floating cages in the Gharraf River on a local bush north of Shatrah city

The current study dealt with the culture of three different densities of common carp, Cyprinus carpio.L. In floating cages in the Garraf River / north of Shatrah city, from 12/2/2020 to 7/7/2021 to obtain the best density of culture per cubic meter. To study the optimal growth, three densities (25-50-75 thickness/m3) were used: 1000 fish for the first treatment, 2000 fish for the second treatment, and 3000 fish for the third treatment, with an average weight ranging between 103 ± 2 and with two replicates for each treatment. One local diet was used for the three treatments, the first treatment recorded a survival rate of 96%, the second 93.3%, and the third 91.98%. The results of the experiment were evaluated according to the following criteria: total weight gain, daily weight gain .Feed conversion rate, feed conversion efficiency. The current study showed the superiority of fish from the first treatment with less significant density than the rest of the treatments, followed by the second treatment and outperformed the third treatment. The chemical analysis showed an increase in the protein contents of the fish body after the experiment for all the treatments in a row, and there were no significant differences for the fish components among the three treatments.

Cultivation of different densities of common carp ( Cyprinus carpio L.1758 ) in floating cages in the Euphrates River in Nasiriyah city

current study was conducted to show the effect of culturing common carp Cyprinus carpio with different densities in floating cages in the Euphrates River in Nasiriyah city, Dhi Qar governorate, on some growth indicators, for a period of (10/17) 2020 until 10/6/2021). Four different treatments were used in the density of culture (200, 300, 400, 500) respectively, and the average weight ranged between (42-55) g. Floating cages made of PVC were used, the same diet was used to feed fish for the four treatments. The results of the current study were evaluated according to growth criteria (total weight gain, daily weight gain, relative growth rate, specific growth rate, food conversion factor, food conversion efficiency, protein efficiency ratio). The results showed that the first treatment, followed by the second treatment, outperformed the third and fourth treatments. It was concluded from the current study that the lowest densities of common carb achieve the best rates of growth indicators.

Submerged macrophytes benefit from lanthanum modified bentonite treatment under juvenile omni‐benthivorous fish disturbance: Implications for shallow lake restoration

Abstract The re‐establishment of submerged macrophytes is crucial in shallow lake restoration transforming a turbid into a clear water system, but it might be inhibited by juvenile omni‐benthivorous fish. These fishes disturb the sediment, and even uproot new sprouts, creating turbid water through sediment resuspension and release of nutrients stored in the sediment. Lanthanum modified bentonite (LMB), an in‐situ capping material, can immobilise phosphate and consolidate sediments, potentially weakening the negative effects of juvenile omni‐benthivorous fish. We hypothesised that applying LMB would improve water quality and promote the growth of submerged macrophytes by eliminating or weakening the increase of suspended solids, nutrient concentration, and algal reproduction due to juvenile omni‐benthivorous fish disturbance. To test our hypothesis, a two‐by‐two factorial mesocosm experiment with two densities of juvenile crucian carp (absence and 10 g/m3) and two doses of LMB (absence and 800 g/m2) was conducted. Juvenile crucian carp significantly inhibited the growth and reproduction of the macrophyte Vallisneria natans by reducing the underwater light and direct effects such as uprooting. No significant inhibition or promotion by LMB on the growth of V. natans in the absence of juvenile crucian carp was observed. However, LMB significantly inhibited the fish‐induced sediment resuspension and nutrients increases. Consequently, algal production was reduced and underwater light conditions were improved, which promoted the growth and reproduction of V. natans, e.g., more ramets, biomass, and leaves of V. natans. Our results indicated that submerged macrophytes could benefit from LMB application under high intensity disturbance by juvenile omni‐benthivorous fish, thereby conducive to the maintenance of a clear water state in shallow lakes.

Of olives and carp: interactive effects of an aquatic and a terrestrial invader on a stream‐riparian ecosystem

AbstractMultiple invasive species may interact, influencing one another and generating synergistic effects on food webs and ecosystem processes. We investigated the interaction between two non‐native species widespread in the western USA: common carp (Cyprinus carpio) and Russian olive (Elaeagnus angustifolia), an invasive riparian tree associated with di‐nitrogen fixation. Deep Creek, Idaho, was an International Biological Program site in the early 1970s; at that time, carp were rare and Russian olive was absent. Subsequently, Russian olive was introduced and established a dense stand, increasing allochthonous inputs and nitrogen‐rich benthic organic matter. Since 1971, carp density has increased ~4× (an increase our bioenergetic analysis suggests could not have been sustained in the absence of Russian olive). Carp gut contents in 2013–2014 revealed, on average, ~40% olives, and, similarly, stable isotope analyses revealed ~58% of carp tissues were derived from olives. A small‐scale, short‐term experimental exclusion of these subsidized carp caused ~3× increases in macrophytes and chlorophyll‐a, suggesting they may limit algae and macrophyte biomass. Moreover, carp that consumed olives excreted more nitrogen (~2× more ammonium, ~2× more total dissolved nitrogen, and ~3× more total nitrogen) compared to those that had not, which may amplify recycling and export from streams invaded by both species. This scenario is characteristic of an “invasional meltdown,” with attendant changes in food webs and ecosystem processes.

Effects of Dietary Paper Mulberry (Broussonetia papyrifera) on Growth Performance and Muscle Quality of Grass Carp (Ctenopharyngodon idella).

Simple SummaryThe quality of muscle plays an important role in improving the economic benefit of aquatic products. The paper mulberry (Broussonetia papyrifera, BP) grows wildly in the south of Asia. In this experiment, grass carps (initial weight: 50.0 ± 0.5 g) were fed diets with the addition of 0%, 5%, 10%, 15% and 20% BP in a control diet (crude protein: 31%, crude fat: 3.8%) for 8 weeks. In conclusion, adding 5% BP did not affect the growth of grass carp. However, the supplementation of 10% BP could improve muscle quality through improving muscle hardness, reducing fat accumulation and muscle fiber diameter, at the cost of reducing growth performance.The present study investigated the effects of dietary paper mulberry (Broussonetia Papyrifera, BP) on growth performance, muscle quality and muscle growth-related mRNA expressions of grass carp. Fish (initial weight: 50.0 ± 0.5 g) were fed diets supplemented with 0% (control diet), 5%, 10%, 15% and 20% BP for 8 weeks. The results showed that increasing levels of paper mulberry linearly and quadratically decreased the special gain rate (SGR) and increased the feed conversion rate (FCR) of grass carp (p < 0.05). Significantly positive quadratic trends were found between paper mulberry levels and muscle crude fat or crude protein of grass carp (p < 0.05). In comparison to the control diet, the 10%BP and 15%BP groups had significantly decreased muscle crude fat and increased crude protein (p < 0.05). The levels of paper mulberry resulted in a linear and quadratic increase in water loss of grass carp muscle (p < 0.05), and all groups with paper mulberry supplementation were significantly higher than the control group (p < 0.05). Significant positive linear and quadratic trends were found between the paper mulberry levels and muscle fiber diameter or density of grass carp (p < 0.05). In comparison to the control diet, the significant differences were found in the 15%BP and 20%BP groups (p < 0.05). The muscle adhesiveness and hardness linearly and quadratically increased with the increasing levels of paper mulberry (p < 0.05), and both of which increased significantly when the level of paper mulberry reached 10% (p < 0.05). In addition, the increase in paper mulberry linearly and quadratically improved the expressions of myoblast determination protein (MyoD), myogenin (MyoG), paired box protein 7 (Pax7) and myostatin 1 (MSTN1) (p < 0.05). When the supplementation of paper mulberry reached 15%, the expressions of all these mRNAs were significantly higher than those of the control group (p < 0.05). In summary, adding 5% paper mulberry did not affect the growth of grass carp. However, the supplementation of 10% paper mulberry could improve muscle quality through improving muscle hardness, reducing fat accumulation and muscle fiber diameter, at the cost of reducing growth performance.

Density‐Dependent Changes in Grass Carp Growth and Mortality in Long‐Term Aquatic Plant Management

AbstractThe Grass Carp Ctenopharyngodon idella is an herbivorous fish that has been stocked throughout the United States for aquatic plant control, commonly to manage hydrilla Hydrilla verticillata. Triploid Grass Carp were purported to have a mean life span of about 11 years based on otolith‐assigned ages and mortality estimates for fish associated with large stocking efforts through which aquatic plants were eliminated. Recent studies in aquatic systems where preferred foods were not eliminated have found that Grass Carp may live up to 30 years or more, but information about growth and mortality is lacking. About 130,000 Grass Carp have been stocked since 1995 to manage hydrilla in combination with fluridone application in Lake Gaston, Virginia–North Carolina, USA. Hydrilla coverage peaked at about 1,300 ha in 2003 and was reduced to about 130 ha by 2014. Since 2006, a total of 419 Grass Carp have been collected for age and growth analysis. A Bayesian approach was used to estimate von Bertalanffy growth function parameters that incorporated the effects of a linear trend in year, hydrilla abundance, or Grass Carp density and to assess population changes. Fish that were stocked in 1995 persisted through 2017. Mean maximum length (L∞) of Grass Carp decreased by about 200 mm with an increasing number of Grass Carp per hectare of hydrilla, and fish reached maximum size earlier in life. Indirect mortality estimates derived from growth parameters increased with Grass Carp density. Because preferred food availability affects mortality rates, stocking numbers should vary accordingly to maximize the effectiveness of hydrilla control programs.

Continental threat: How many common carp (Cyprinus carpio) are there in Australia?

Common carp (Cyprinus carpio) are one of the world's most destructive vertebrate pests. In Australia, they dominate many aquatic ecosystems causing a severe threat to aquatic plants, invertebrates, water quality, native fish and social amenity. The Australian Government is considering release of cyprinid herpesvirus-3 (CyHV-3) as a control measure and consequently a robust, continental-scale estimate of the carp population and biomass is essential to inform planning and risk management. Here, we pioneer a novel model-based approach to provide the first estimate of carp density (no/ha) and biomass density (kg/ha) at river reach/waterbody, basin and continental scales. We built a spatial layer of rivers and waterbodies, classified aquatic habitats and calculated the area of each throughout the range of carp in Australia. We then developed a database of fishery-independent electrofishing catch-per-unit-effort (CPUE) for habitat types, containing catch information for 574,145 carp caught at 4831 sites. Eastern Australia accounted for 96% of carp biomass and 92% of the total available wetted habitat area (16,686 km2) was occupied. To correct these data for variable detection efficiencies, we used existing electrofishing data and undertook additional field experiments to establish relationships between relative and absolute abundances. We then scaled-up site-based estimates to habitat types to generate continental estimates. The number of carp was estimated at 199.2 M (95%Crl: 106 M to 357.6 M) for an ‘average’ hydrological scenario and 357.5 M (95%Crl: 178.9 M to 685.1 M) for a ‘wet’ hydrological scenario. In eastern Australia, these numbers correspond with biomasses of 205,774 t (95%Crl: 117,532–356,482 t) (average scenario) and 368,357 t (95%Crl: 184,234–705,630 t) (wet scenario). At a continental scale the total biomass was estimated at 215,456 t for an ‘average’ hydrological scenario. Perennial lowland rivers had the highest CPUE and greatest biomass density (up to 826 kg/ha) and the modelled biomass exceeded a density-impact threshold of 80–100 kg/ha in 54% of wetlands and 97% of stream area in large lowland rivers. The continental-scale biomass estimates provide a baseline for focusing national conservation strategies to reduce carp populations below thresholds needed to restore aquatic ecosystems at a range of spatial scales.

Cultivation of different densities of common carp ( Cyprinus carpio L.1758 ) in floating cages in the Euphrates River in Nasiriyah city

Cultivation of different densities of common carp ( Cyprinus carpio L.1758 ) in floating cages in the Euphrates River in Nasiriyah city

Case Studies Demonstrate That Common Carp Can Be Sustainably Reduced by Exploiting Source-Sink Dynamics in Midwestern Lakes

The common carp has been highly problematic in North American ecosystems since its introduction over a century ago. In many watersheds, its abundance appears to be driven by source-sink dynamics in which carp reproduce successfully in peripheral ponds that lack egg/larva micro-predators which then serve as sources of recruits for deeper lakes. This manuscript describes how carp were sustainably reduced in two chains of lakes by disrupting source-sink dynamics in three steps. First, we ascertained whether lakes had problematic densities of carp that could be explained by source-sink dynamics. Second, ways to control recruitment were developed and implemented including: (i) aerating source ponds to reduce hypoxia and increase micro-predator abundance, (ii) blocking carp migration, and (iii) locating and removing adults from sinks using targeted netting guided by Judas fish. Third, we monitored and adapted. Using this strategy, the density of carp in 3 lakes in one chain was reduced from 177 kg/ha to ~100 kg/ha in 3 years and held constant for a decade. Similarly, adult density was reduced from 300 kg carp/ha in 2 lakes in the other chain to 25 kg/ha. Once carp densities were low, aluminum sulfate treatments became reasonable and once conducted, water quality improved.