The dominance of algal-based food webs in fish ponds receiving chemical fertilizers plus organic manures
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Polyculture
Grass carp
Detritus
Bighead carp
Polyculture
Grass carp
Common carp
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Aquaculture has become a primary method to produce various aquatic products, and intensive aquaculture technologies have become commercially important. To improve the efficiency of intensive aquaculture per unit area without reducing the growth rate of cultured fish, the present study explored the potential of artificial substrata in ponds. Our results showed that the concentrations of total nitrogen (TN) and total phosphorous (TP) in the ponds with different stocking densities of grass carp were lower than those in the control group in most cases. Further, the feed conversion rate of grass carp was significantly reduced by introducing these artificial substrata, and the culture density could be significantly increased without reducing the growth rates of these fish. Artificial substrata also significantly enriched specific bacteria and changed the structure of the microbiota in pond water. The relative abundance of Proteobacteria was significantly increased, and bacteria closely related to N and P cycles, such as Hyphomicrobium , Chitinimonas , Legionella , Shewanella , Roseiflexus , and Planktothrix were significantly enhanced. These results showed that the artificial substratum could increase TN and TP removal in aquaculture pond water by enriching N and P cycle-related bacteria, thus significantly increasing the specific growth rate of grass carp and significantly reducing their feed conversion rate. Finally, the stocking density of grass carp and the yield per unit area of pond could be increased without reducing the growth rate.
Grass carp
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Polyculture
Grass carp
Common carp
Commercial fish feed
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Polyculture
Common carp
Grass carp
Hypophthalmichthys
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Abstract In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T‐I) (control treatment); 2) 6‐wk delay of feeding after fish stocking (T‐II); 3) 13‐wk delay of feeding after fish stocking (T‐III), and 4) no supplemental feed application (T‐IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T‐I, T‐II, and T‐III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T‐II showed weight gain, growth rates, and yields significantly higher than fish in T‐III or T‐IV. Also, the total fish production and net profit in T‐II were significantly higher than in T‐III or T‐IV. Fish species in T‐II showed weight gain, growth rates, survival rates, and yields similar to those of T‐I (control treatment) with no significant differences. The amount of feed consumed by fish in T‐II was reduced by approximately 7.3% compared to that consumed by fish at T‐I. Moreover, there was increase in th net profit in T‐II by 4.8% over that achieved in T‐I. Therefore, T‐II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.
Polyculture
Nile tilapia
Common carp
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Bighead carp
Grass carp
Polyculture
Common carp
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It is shown that the leading role in the aquaculture of Iraq belongs to Cyprinids, which account for over 80 % of all fish farming production. The most widespread in the country are four main world species of carp aquaculture: common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis). Basically, the traditional technology of growing Cyprinids in ponds is used, which includes the main fish farming processes: care of broodstock to prepare them for spawning, collecting eggs and milt, eggs fertilization and incubation of embryos, raising juveniles and marketable fish. Currently, there are about 2 thousand private fish farms, which have ponds of various sizes from 4 to 100 hectares. Cultivation of Cyprinids in Iraq is carried out mainly by extensive methods: the use of the natural food base of reservoirs with low fish stocking density in polyculture. The fish productivity of ponds varies greatly in different fish farms from 1,5 to 6 t/ha, which is due to economic reasons. The data on changes in the temperature of pond water during the year and hydrochemical indicators are given, which shows favorable conditions for Cyprinids rearing. Information on the use of compound feeds for growing carp in ponds is provided, and data on the composition and nutritional value of the feed used. The fish culture indicators for the main biotechnical processes of the rearing of four Cyprinid species in Iraq are described in detail. In the conclusion, it is indicated that for the effective development of aquaculture in Iraq, government support is needed in the form of a developed long-term program and legislative acts.
Polyculture
Broodstock
Bighead carp
Common carp
Hypophthalmichthys
Grass carp
Commercial fish feed
Milt
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Polyculture
Common carp
Catla
Grass carp
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The experiment was conducted to determine the effects of fish population density on the growth and production of carps fries (Silver carp, Mirror carp and Rui) in polyculture for a period of 90 days in earthen ponds. Mean individual stocking weight (wt) (g) of the fry of silver carp, mirror carp and rui were 0.10, 0.103 and 0.08 under treatment-I and were 0.17, 0.142 and 0.11 under treatment-II. In the ponds under both treatments, inorganic and supplementary balanced feed (50% per body weight) was used to the cultured ponds for spawn to fish fingerlings. During the experimental period, the ranges of water temperature (26 to 34 0 C), transparency (28 to 41 cm), dissolved oxygen (2.45 to 5.5 mg/L), pH (7.0 to 8.5), total alkalinity (130 to 182 mg/L), and ammonia nitrogen (0.12 to 0.3 mg/L) found were within the productive limit and more or less similar in all the ponds under treatment-I and II. The survival rate of silver carp was 38.60 and 66.48 under treatments I and II. The survival rate of mirror carp was 31.20% and 45.50% under treatment I and II and the survival rate of rui was 31.51% and 53.35% under treatment I and II, respectively. The calculated net fish production of the ponds under treatment-I was 1905.13±141.95 kg ha -1 90d -1 and that of the ponds under treatment-II was 3831.74±411.35 kg ha -1 90d -1 . It was found that net fish growth, survival rate and productions was better in treatment-II than treatmentI. Finally it is concluded that the growth, survival rate and production of fry up to fingerlings would be better by intervention of proper stocking density of various fish species in pond fish culture.
Hypophthalmichthys
Polyculture
Alkalinity
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Fish farming is the only type of aquaculture in Serbia. Fish farming is mostly carried out in cyprinid and salmonid (trout) fishponds (over 95% of the total fish produced), with considerably lower ichthyoproduction being practiced in cages and some bodies of open water such as reservoirs and channels. Serbian aquaculture currently includes 12 fish species, 4 of which are allochthonous (non-native). With the exception of the rainbow trout (Oncorhynchus mykiss) and, to a certain extent, grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), allochthonous fish species have no economic importance. The presence and abundance of certain allochthonous species in fishponds and open waters have a negative effect on the total ichthyoproduction.
Hypophthalmichthys
Polyculture
Bighead carp
Grass carp
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