Filter-feeding Carp Research Articles

Nontraditional biomanipulation: A powerful ecotechnology to combat cyanobacterial blooms in eutrophic freshwaters

<p>Cyanobacterial blooms, occurring frequently in eutrophic freshwaters worldwide, are considered as potential hazards to ecosystems and human health, and it is often difficult and expensive to control their outbreaks in large lakes through reduction of nutrient loadings. Biomanipulation, launched as an ecology-based solution in the 1970s, was once believed to be an effective way to counteract cyanobacterial blooms. It is divided into traditional biomanipulation (TB) and nontraditional biomanipulation (NTB) that use filter-feeding <i>Daphnia</i> and filter-feeding fish, respectively. There have been numerous reviews on the former, yet few on the latter. Here, we first revisit the debate on the digestibility of cyanobacteria in silver and bighead carp. Then, we review 42 experiments that clearly mention cyanobacterial changes and reveal substantial reductions in cyanobacterial abundance by filter-feeding carp in 88% of the cases. In particular, in a whole-lake experiment in Lake Donghu, increased stock of silver and bighead carp effectively decreased <i>Microcystis</i> blooms from a coverage of 87% in 2021 to 0% in 2022. Finally, we discuss possible factors related to NTB��s effectiveness that depends not only on standing stock, niche divergence and shape preference of the fish but also on trophic status of the waterbodies. Particularly, silver and bighead carp feed more effectively on colony-forming <i>Microcystis</i> than on filamentous cyanobacteria, but are capable of increasing small-sized algae. NTB can be used to prevent or diminish cyanobacterial blooms that are poorly grazed by <i>Daphnia</i>, providing an effective and sustainable in-lake ecotechnology to combat heavy cyanobacterial blooms in eutrophic waterbodies.</p>

Comparative analysis of bacterial communities of water and intestines of silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) reared in aquaculture pond systems

Silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) are the most common filter-feeding fish species. Distinct niches of these two species lead to differences in their ecological function. Here, high-throughput sequencing of 16S rRNA gene was employed to investigate and compare the bacterial community and potential function of silver carp and bighead carp reared in aquaculture pond systems. We found no significant difference in alpha diversity between microbial community of water body and intestinal microbiota of silver carp and bighead carp. Bacterial community richness of bighead carp, however, was higher than that of silver carp. A significant separation between microbial community of water body and of two fish species was observed. The Norank_o__PeM15, norank_f__Alcaligenaceae and unclassified_p__Firmicutes were higher for bighead carp but only Pseudomonas was higher for silver carp. Compared with bighead carp, intestinal microbiota of silver carp also had less typical planktonic bacteria. A separation but non-significant of bacterial community between silver carp and bighead carp was observed. In terms of predicted community function for water body, except for the lower abundance of cell motility than silver carp, the other pathways were generally more enriched than the two fish species. For the comparison between silver carp and bighead carp, most metabolic pathways, e.g., nutrients transport and metabolism, were generally more enriched for silver carp. The results of this study gain a better appreciation of gut microbiome ecology relating to pond culture of two species of microphagic filter-feeding carps, which could be effectively used in the management of these two species to enhance production and health.

Biological manipulation of eutrophication in West Yangchen Lake

This paper aims to share findings on nonclassical biomanipulation from a field study on eutrophic West Yangcheng (WY) Lake. In the forty years before 2009, cyanobacteria frequently bloomed in WY Lake, an event which has not occurred since 2009. The stocking density of filter-feeding carp was estimated to be more than 50 g/m3 in July after 2009, approximately double the amount observed before 2009, and the ratio of silver carp to bighead carp (SBR) increased from 0.8 to more than 1.6. Compared with the water quality between 2004 and 2007, the total nitrogen (TN) and the chlorophyll-a (Chl-a) concentration decreased while total phosphorus (TP) and transparency (SD) increased significantly after 2009 (P < 0.05). The decreasing Chl-a concentration was observed in Jul, Jun, May, Jul, and Mar in 2009, 2010, 2011, 2016, and 2017, respectively. The Chl-a concentration was significantly negatively correlated with TP (P < 0.05), and no significant correlation with TN was observed (P > 0.05). A significant negative correlation was observed between fish yield and SD (P < 0.05). The results also showed that filter-feeding carp more effectively restrained algae growth when SD was low. These results indicated that a high density of filter-feeding fish with increased SBR interfered with the driving effects of nutrients and temperature on the growth of algal biomass and then restrained bloom of algae. It may be necessary to take SD into consideration for determining the appropriate fish stocking density for the biomanipulation of algae.

Intra-annual variation of zooplankton community structure and dynamics in response to the changing strength of bio-manipulation with two planktivorous fishes

Zooplankton is widely used in indicating environmental changes and energy flow efficiency in aquatic ecosystems. Species composition and body size spectrum of zooplankton assemblage are sensitive to the changes of physico-chemical variability and fish feeding stress, and thus have in turn a prime bearing on water quality and cultured fishes. To study the response of zooplankton community to the introduction of planktivorous carps, monthly surveys were conducted in 2015 at six traditionally monitored locations in Miyun Reservoir, the unique surface drinking water of Beijing. There was a decrease in species richness, diversity, density and biomass, suggesting simplification of the community structure. Species diversity, density, and biomass declined significantly through the growth season, illustrating the great pressure imposed on the zooplankton. Regression and canonical correspondence analysis (CCA) showed low relationships between community traits and environmental variables. Zooplankton biomass had a significantly negative relationship with the stocking intensity of the filter-feeding carp. The different responses of the subgroups of Protozoa, Rotifera, Cladocera and Copepoda indicated that they responded differently to environmental stress. Seasonal variations in the density and biomass of the four subgroups and biomass size spectrum (BSS) indicated that planktons with medium and large body sizes were more sensitive and suffered more stress from the filter-feeding carp. The filter feeding by the silver and bighead carp disrupted the natural equilibrium of the zooplankton community, decreased diversity and stocks, altered the seasonal dynamics of all quantitative traits and suppressed the dominance of medium- and large-sized species or functional groups. The impacts of the fishery mode and the responses of different functional groups of zooplankton must be considered in ecological assessments and biomanipulation studies based on the zooplankton community structure and dynamics.

Effects of organic carbon addition on water quality and growth performance of bottom- and filter-feeding carp in a minimum-water-exchange pond polyculture system

A 120-day evaluation was performed to determine the impacts of various carbon source supplements on the water grade and production of bottom- and filter-feeding carp inside a minimum-water-exchange system. The outcomes revealed that the overall ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total inorganic nitrogen, and orthophosphate concentrations in every one of the carbon source treatments were significantly less (P < 0.05) than the control. The net production of silver carp and bighead carp in the molasses treatment was significantly higher (P < 0.05) than that in the control. The total feed conversion rates of the fish in the molasses and the mixed carbon source treatments were significantly lower (P < 0.05) than in the control, while the total protein efficiency ratio values in the corn starch, molasses, and mixed carbon source treatments were significantly higher (P < 0.05) than those in the control. The bioflocs significantly (P < 0.05) impacted the muscle makeup of crude protein, crude fat, and ash of mirror carp. The current examination showed that the increased generation and feed used in mirror, silver, and bighead carp may be reached with an enhanced water grade when different carbon sources were added, while the use of molasses, an organic carbon source, was optimal compared to the other carbon sources due to its low price and good effect.

An improved methodology for calculating the nitrogen footprint of seafood

Human activities create more reactive nitrogen than is created through natural processes every year. The excess reactive nitrogen in the environment causes various negative effects including eutrophication, climate change, acidification, and human health problems. The sources of the excess nitrogen are mainly fertilizers and animal and human waste generated by food production and consumption. Therefore, our food choices have major effects on the nitrogen load to the environment. To quantify the load, a consumption-based accounting tool, called the nitrogen footprint, has been recently developed. In current nitrogen footprint models, seafood is calculated as a single category using the same simple assumptions as livestock. However, there is a variety of types and methods of production of seafood. In addition, world per capita consumption of seafood is projected to continue expanding. In this paper, we propose a new nitrogen footprint model to evaluate the impact of seafood in detail, present the results of the model applied to Japan as a case study, and explain the important parameters that are needed to accurately evaluate the load of seafood consumption. Our model tracks the feeding steps in detail, considering differences among fed aquacultured seafood, non-fed aquacultured seafood (mainly bivalves and filter-feeding carp), and captured seafood. Our model evaluates the Japanese food nitrogen footprint of fed aquacultured seafood as 0.7kg-N/capita/year, ca. 45% of that of all seafood, whereas the previous model evaluates it as 3.36kg-N/capita/year. Our results demonstrate that the key factors for assessing the nitrogen load of seafood are the proportions of fed aquaculture and of plant protein in feed. In order to enable food choices that will effectively reduce nitrogen release, we provide the virtual N factors (per intake nitrogen release during production) for different seafood as 0.2 (non-fed aquacultured and captured), 4.8 (freshwater and diadromous fish), 3.9 (demersal fish), 3.4 (pelagic fish and other marine fish), and 8.2 (crustaceans). Our results show that eating more non-fed aquacultured and captured seafood and less fed-aquacultured shrimps and prawns could reduce our nitrogen load from food consumption as effectively as choosing poultry instead of beef. Although its evaluation is limited to nitrogen load related to food itself and not including the load from energy use, etc., our detailed nitrogen footprint model for different seafood categories and production sources can quantify the effectiveness of policies and actions that link sustainable consumption and sustainable fisheries and aquaculture, contributing toward the Aichi Biodiversity Targets.

Do physicochemical variables regulate the distribution of zooplankton communities in reservoirs dominated by filter-feeding carp?

The temporal and spatial distributions of zooplankton communities in the upper, middle, and lower reaches of the Xin’anjiang Reservoir, Zhejiang, China, were investigated monthly, between 2009 and 2010. Silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) dominated the pelagic fish community of this large, deep reservoir. Cladocerans were distributed evenly throughout the reservoir. Rotifers were mainly found in the upper reaches, while copepods tended to assemble in the lower reaches. The Pearson correlation analysis and stepwise multiple regression were used to identify the major physicochemical gradients influencing community variations. Zooplankton community distributions were influenced by water temperature, dissolved oxygen, phosphorus, nitrogen, and silicon. Excess nutrients, in particular silicon, stimulated rotifer growth. Based on these findings, it is possible to use rotifer density as a bioindicator of eutrophic status in deep reservoir ecosystems.

The food web structure and ecosystem properties of a filter-feeding carps dominated deep reservoir ecosystem

An Ecopath model was constructed to describe the ecosystem of Lake Qiandaohu, a stock-enhanced large deep Chinese reservoir with silver carp ( Hypophthalmichthys molitrix) and bighead carp ( Aristichthys nobilis) dominated in its pelagic community. The food web structure and ecosystem property of the reservoir were analyzed and evaluated. The results showed that there were seven trophic levels (TLs) in the system, with the trophic flows primarily occurring through the first four TLs. The food web structure of this ecosystem was characterized with a bulged intermediate trophic level, which was contrary to the wasp-waist food web structure occurred in most natural aquatic ecosystems. The corresponding trophic flow pattern showing by transfer efficiencies (TEs) between TLs indicated that the trophic flows primarily went through from TL I to II with a high TE (of over 50%) and through a flow loop or short cut between detritus and TL II but greatly reduced from TL II to III with a lowest TE of 2.5% due to the bulged biomass at TL II. The trophic flow loop greatly increased the throughput recycled, which, together with high connectance index (CI), system omnivory index (SOI), Finn's cycled index (FCI) and Finn's mean path length (FML), might be beneficial to the maintaining of ecosystem stability. Finally, ecosystem property indices showed that this reservoir had a high value of P p/ R and P p/ B, indicating this ecosystem of short history was immature, but highly productive. This silver carp and bighead carp dominated deep reservoir ecosystem had both the characteristics of high productivity of an immature ecosystem and the feature of high stability of a mature ecosystem.

Ingestion of bacteria in suspension Indian major carps (Catla catla, Labeo rohita) and Chinese carps (Hypophthalmichthys molitrix, Aristichthys nobilis)

Single-species groups of fry of the planktivorous, filter-feeding carps (silver carp Hypophthalmichthys molitrix, bighead carp Aristichthys nobilis, rohu Labeo rohita and catla Catla catla) were exposed to the bacterium Chromobacterium violaceum to assess if they could detect or ingest unattached bacteria. The results indicate that planktivorous carp fry are able to ingest unattached bacteria and that the numbers ingested increase with time and with bacterial concentration in the media, although probably by passive means. It is also suggested that unattached bacteria are of little nutritional significance to carps.