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Abstract One of the primary sustainability challenges in aquaculture is replacing fish meal with plant‐based ingredients in aquafeeds. Plants are not optimal due to low protein content and antinutritional factors which can cause gut dysbiosis. Duckweed (Lemnaceae) is a family of aquatic plants with high protein content and has been used successfully for various types of animal feeds. In this systematic review and meta‐analysis of 58 papers, we summarize the extent by which duckweed has been used in fish production including the species of fish tested, the grow‐out stage of fish, and method of application. Duckweed studies spanned a total of 18 species of fish (16 freshwater and two marine) that collectively are valued at 263 billion USD annually, and comprise 28% of total aquaculture production by mass. The average experiment length was 72 days (SD 42), primarily at the fingerling life stage. Duckweed was fed to the fish through live grazing, dried, and pelleted forms with 20% inclusion as the most common formulation. TheLemnaspp., dominated byL.minor,L.gibba, and unknownLemnaspecies, were the most commonly used for feeds.Spirodela polyrhizawas the second most common. Duckweed inclusion levels between 15% and 30% were associated with positive outcomes on fish growth and feed conversion ratio without any negative impact on survival rates. Most duckweed species, especially fromWollfiellahave not been tested as a fish feed but should be explored whereas most studies focused on freshwater fishes rather than marine.
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Four decades of nitrous oxide emission from Chinese aquaculture underscores the urgency and opportunity for climate change mitigation
Abstract As the fastest growing food production sector in the world, aquaculture may become an important source of nitrous oxide (N2O)—a potent greenhouse gas and the dominant source of ozone-depleting substances in the stratosphere. China is the largest aquaculture producer globally; however, the magnitude of N2O emission from Chinese aquaculture systems (CASs) has not yet been extensively investigated. Here, we quantified N2O emission from the CASs since the Reform and Opening-up (1979–2019) at the species-, provincial-, and national-levels using annual aquaculture production data, based on nitrogen (N) levels in feed type, feed amount, feed conversion ratio, and emission factor (EF). Our estimate indicates that over the past 41 years, N2O emission from CASs has increased approximately 25 times from 0.67 ± 0.04 GgN in 1979 to 16.69 ± 0.31 GgN in 2019. Freshwater fish farming, primarily in two provinces, namely, Guangdong and Hubei, where intensive freshwater fish farming has been adopted in the past decades, accounted for approximately 89% of this emission increase. We also calculated the EF for each species, ranging from 0.79 ± 0.23 g N2O kg−1animal to 2.41 ± 0.14 g N2O kg−1animal. The results of this study suggest that selecting low-EF species and improving feed use efficiency can help reduce aquaculture N2O emission for building a climate-resilient sustainable aquaculture.
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- Award ID(s):
- 1903722
- PAR ID:
- 10306050
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 16
- Issue:
- 11
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- Article No. 114038
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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