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Rebuttal to “a revisit to fishmeal usage and associated consequences
in Chinese aquaculture”
Ling Cao1,*, Rosamond Naylor1 , Patrik Henriksson2,3, Duncan Leadbitter4, Max Troell3, 5, Wenbo Zhang6
As authors of “China’s aquaculture and the world’s fisheries” (Cao et al., Science, 2015), we
would like to dispute several claims presented in “A revisit to fishmeal usage and associated
consequences in Chinese aquaculture” (Han et al.,§ Reviews in Aquaculture, 2016), as the latter
seriously misrepresents the intent and substance of our Science paper.
In their review, Han and colleagues argue that although China’s aquaculture volume continues to
grow, its fishmeal usage remains stable, and the sector will therefore indirectly reduce pressure
on wild fish stocks worldwide. In the process, they claim that we do not acknowledge the
important contribution of the Chinese aquaculture sector to global food supply. They also claim
that we criticize the sector’s excessive use of fishmeal and that we trot out the “Chinese
aquaculture threat” theory. We are aware of Han and colleagues’ comprehensive work on
substitution and sustainable sourcing of fishmeal and fish oil in aquaculture, which is clearly
aligned with our perspective. However, we believe that the underlying intention of our Science
paper has been seriously misinterpreted, and there are several inaccuracies in their review that
are important to clarify and correct.
Here, we emphasize and reiterate the key points in our paper: China’s impact on marine
ecosystems and global seafood supplies is unrivaled given its dominant role in fish production,
consumption, processing and trade. Its aquaculture sector, by far the world’s largest, is of
enormous global importance for meeting the rising demand for food and particularly for protein.
Understanding the implications of the industry’s past and current practices is important for
1Center on Food Security and the Environment, Stanford University, Stanford, CA 94035, USA. 2WorldFish, Penang, Malaysia
3Stockholm Resilience Centre, Stockholm University, 106 91 Stockholm, Sweden. 4University of Wollongong, Wollongong
NSW 2522, Australia. 5The Royal Swedish Academy of Sciences, 104 05 Stockholm, Sweden. 6Shanghai Ocean University,
Shanghai 201306, China. *Correspondence should be addressed to L. Cao (email: caoling@stanford.edu).
§Han, D., Shan, X., Zhang, W., Chen, Y., Wang, Q., Li, Z., Zhang, G., Xu, P., Li, J., Xie, S., Mai, K., Tang, Q., De Silva, S.
(2016), Reviews in Aquaculture. Article in Press.
managing its future impacts and improving its sustainability. The country’s nonspecific and
erroneous reporting of fish production and trade makes it especially difficult to access the impact
of China’s aquaculture and aquafeed use on global wild fisheries. We unraveled the complicated
nature of China’s expanding aquaculture sector and its multifaceted use of fish inputs in feeds, to
the best of our abilities. We also developed a roadmap for China’s aquaculture to become self-
supporting of fishmeal by recycling processing wastes from its farmed products as feed. We
showed that if food safety and supply chain constraints can be overcome, extensive use of fish
processing waste in feeds could help China meet one-half or more of its current fishmeal
demand, thus greatly reducing pressure on domestic and international fisheries. In addition, we
suggested China to commit to stricter enforcement of regulations on capture fisheries and to
responsible sourcing of fishmeal and fish oil, as well as to improve its data reporting and sharing
on the status of fisheries stocks, aquaculture practices, production, and trade.
We would like to respond specifically to the following points in Han et al (2016):
1. “Role of China’s aquaculture in meeting the rising demand for fish at home and abroad is not
acknowledged by Cao et al., 2015.”
Our response: Our paper conveys a clear message that China’s aquaculture industry is by far
the world’s largest and of great importance for meeting the rising domestic and global
demand for fish and protein.
2. “China contributes more than 60% to the global aquaculture output and is expected to
contribute 38% to the global food fish supply by 2030, however costs only 25-30% of the
world fishmeal. The above facts are contradictory to the views expressed that Chinese
aquaculture is a threat to the world’s wild fish resources (Cao et al., 2015). China’s
aquaculture and aquafeed industry have some special features leading to the steady fishmeal
usage, which consequently does not impose additional stressors on the world wild fish
stocks, drawing a conflicting conclusion to that found in Naylor et al. (2000, 2009) and Cao
et al. (2015).”
Our response: Our paper clearly indicates that China is a net contributor of fish (fed fish).
The table in our paper shows that from 5 million metric tons (mmt) forage fish equivalents,
14.4 mmt of finfish and shrimp were produced in 2012 (21 mmt is the total but with the non-
fed carp species having been subtracted). Moreover, we write: “If China is to increase its net
production of fish protein, its aquaculture industry will need to reduce FCRs and the
inclusion of fish ingredients in feeds and to improve fishmeal quality”. Thus, we are not
asserting that China consumes more fish than the fed fish it produces, but rather we are
challenging the industry to further increase its current net production of fish protein.
!
While China’s fishmeal import has been stable at a level of 1-1.5 mmt over the past decade,
it should be noted that the use of fishmeal for aquaculture has increasingly been diverted
from the livestock to aquaculture sector. There are no official statistics specifying in which
sector the fishmeal is used. One market trend study published in Chinese stated that the share
of fishmeal use for aquaculture in China has exceeded the share used by livestock since 2010,
growing from 38 percent (0.73 mmt) in 2005 to 64 percent (0.96 mmt) in 2011 (see Fig. 1).
Our observation is consistent with the literature that supports a trend of shifting in fishmeal
use from other sectors towards aquaculture (De Silva and Turchini, 2008).
We agree that China has made remarkable progress in identifying alternative ingredients for
substituting fishmeal and fish oil in aquafeeds, especially for low-trophic level species. We
are more concerned with the high inclusion rate of fishmeal in high-trophic carnivorous
species and using trash fish as feeds for aquaculture.
Figure 1. Fishmeal use in China (Chen 2012)
0.73 0.71 0.7 0.69
0.8 0.74
0.96
1.18
0.62 0.53
0.83 0.8
0.39
0.54
0
0.2
0.4
0.6
0.8
1
1.2
1.4
2005 2006 2007 2008 2009 2010 2011
Million metric tons
consumed by aquaculture consumed by livestock
3. “The observed trends reflect in the figures indirectly provides support to the notion that
Chinese aquaculture production increases could be well achieved with reduced fishmeal use.”
Our response: This statement is actually in line with what we observed. We believe that
China can increase its net production of fish protein with reduced fishmeal use by responsible
sourcing and substitution of fish ingredients in feeds. We explored the potential of recycling
fish-processing wastes as aquafeeds and show how this can further reduce China’s overall
dependence on capture fisheries while increasing net fish supplies. Performing this type of
analysis does not take away the overall positive characteristics of Chinese aquaculture sector
as a net producer of seafood.
4. “China is a leader in low trophic level aquaculture production that is sparsely acknowledged,
particularly by critiques of Chinese aquaculture.”
Our response: We acknowledge China’s leading role in low-trophic level aquaculture. We
wrote in our paper that in 2012, China produced more than 90% of the world’s carp. With
increased pressure on land and water resources associated with rapid economic growth,
aquaculture systems throughout China are intensifying. Producers are moving away from
traditional low-input carp systems into monoculture or polyculture systems that containing
high-valued species dependent on fish. We believe that the diversity and low-trophic level
base of China’s aquaculture provides substantial opportunity for positive change. We
encourage China to continue working on reducing FCRs and improve the inclusion rate of
fish ingredients in feeds.
5. “China’s domestic fishmeal production is based on processing waste and trash fish.”
Our response: Han and colleagues confirmed our observations. However, we are more
concerned with the impacts of harvesting low-value trash fish species on the structure and
functioning of marine ecosystems and global food security (Smith et al., 2011). Multi-species
(non-targeted) catch, commonly designated as “marine fish nei” (nei: not elsewhere included)
by FAO, surpasses the catch of any individual species in China’s ocean capture fisheries.
Combined with by-catch and other poor quality fish from targeted fisheries, it is a major
contributor to what the international research community often refers to as low-value “trash
fish”. Although these fish resources are considered to be “low-value” in the market, they are
derived from fisheries that have a higher social value for direct human consumption and
marine ecosystems (Tacon et al., 2006). Whilst it is true that trash fish includes naturally
small fish, it is also true that significant numbers of juvenile fish are also taken and, in
combination with poorly regulated fisheries, this take of juvenile fish undoubtedly
contributes to the poor status of many fish stocks. Virtually all of the fish hauled out of the
ocean by Chinese vessels are put to economic use, first for human consumption, and then for
feeds and other purposes. Large amounts of trash fish are being used for fishmeal production
and China’s high-value marine aquaculture uses around 3 mmt of trash fish each year for
direct feeding. Notwithstanding the improvements in feed efficiency demonstrated by Han et
al relieves the issue of overfishing, China’s increased use of trash fish for aquaculture
deserves further investigation.
6. Data quality issue: “Survey data in the studies of Chiu et al. (2013) and Cao et al. (2015)
from only four provinces of China, Guangdong, Shandong, Zhejiang, and Hainan don’t fully
represent the status of Chinese aquaculture, in particular freshwater aquaculture.”
Our response: We present data and analyses based on not only primary field surveys and
observations from the four major aquaculture producing regions in China, but also on
national production and trade statistics, and scientific papers from the Chinese and
international literature. We use the same national fisheries statistics databases as Han and
colleagues do. In terms of our field data collection, Guangdong and Shandong provinces are
the top two aquaculture producers in China. The four provinces together account for over one
third of China’s aquaculture production and one quarter of its freshwater aquaculture output
by volume. The field data were based on in-depth field surveys conducted by Stanford
University and the EU-FP7 Sustaining Ethical Aquaculture Trade (SEAT) project during the
year of 2010-2012. The surveys focused on carp, tilapia, and shrimp systems, which
represent three of the largest aquaculture sub-sectors in China along a spectrum of low- to
high-valued species and account for over 50% of the country’s aquaculture output by
volume. So we are confident that the provinces that we selected are representative for the
farming systems in focus.
As highlighted in both publications, obtaining this type of data from China is notoriously
difficult. Our reliance on information from only four provinces is due to the lack of publicly
available studies of trash fish catches in other studies and the lack of regular monitoring of
catches and stock status. Given the uncertainty involved and the difficulty in obtaining more
accurate data, we have endeavored to provide the best available data from primary and
secondary sources in order to demonstrate how dependence on fishmeal from targeted and
non-targeted fisheries can be substantially reduced. In order to bring as much rigor to the
analysis as possible, we have also incorporated uncertainty analysis via Monte Carlo
simulation. Many scientists agree that this is a fair approach and our analysis is valid.
Closing Remarks
There is no question that China’s aquaculture will remain a dominant industry domestically and
internationally in the future. At the global scale, the sector has expanded at an annual rate of
8.8% during the past three decades—faster than any other animal food sector—and it currently
accounts for about half of all fish produced for human consumption. Within this dynamic
context, China’s aquaculture sector remains an important “black box” for many scientists and
policy analysts with respect to farming practices, aquafeed demand, domestic fishmeal
production, trash fish consumption, and impacts on global capture fisheries. Our paper helps to
crack open this black box, and it provides an integrated and innovative perspective on the status
and trends of China’s aquaculture development. If Han and colleagues have more accurate data
to share, we would be more than happy to take these data into account in our attempt to map the
fishmeal use in China and steer China’s aquaculture industry towards best practice. To that end,
we recommend that China establishes a public process for data reporting and sharing on fisheries
stock status, aquaculture practices, production, and trade.
!
We hope these responses have clarified the misinterpretations of our paper by Han et al. (2016),
and that these points can be corrected accordingly. It is important to note that we, the study
authors, and Han et al. are clearly united in the recognition that China’s aquaculture industry is a
key component of meeting the country’s and the world’s growing protein needs. We also agree
on the importance of sustainable aquaculture practices in China that safeguard the health of wild
fisheries at home and abroad. We truly believe in China’s commitment to the development of
more sustainable and responsible aquaculture practices based on ecological principles. We look
forward to a more positive intellectual exchange with Han and colleagues in the future as we
strive for this common goal.
References
Cao, L., Naylor, R.L, Henriksson, P., Leadbitter, D., Metian, M., Troell, M., & Zhang, W.
(2015). China's aquaculture and the world's wild fisheries. Science, 347(6218), 133-135.
Chen, M. (2012). Fishmeal Market Analysis and Outsourcing Strategy in 2012 (in Chinese).
Fisheries Advance Magazine, (4), 95–97. Available at:
http://d.wanfangdata.com.cn/Periodical_hyyyy-scqy201204059.aspx.
Chiu, A., Li, L., Guo, S., Bai, J., Fedor, C., Naylor, R.L. (2013). Feed and fishmeal use in the
production of carp and tilapia in China. Aquaculture, 414, 127-134.
De Silva, S. S., and Turchini, G. M. (2008). Towards understanding the impacts of the pet food
industry on world fish and seafood supplies. Journal of agricultural and environmental
ethics, 21(5), 459-467.
Han, D., Shan, X., Zhang, W., Chen, Y., Wang, Q., Li, Z., Zhang, G., Xu, P., Li, J., Xie, S., Mai,
K., Tang, Q., De Silva, S. (2016). A revisit to fishmeal usage and associated
consequences in Chinese aquaculture. Reviews in Aquaculture. In press.
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Lubchenco, J., Mooney, H. and Troell, M. (2000). Effect of aquaculture on world fish
supplies. Nature, 405(6790), 1017-1024.
Naylor, R.L., Hardy, R.W., Bureau, D.P., Chiu, A., Elliott, M., Farrell, A.P., Forster, I., Gatlin,
D.M., Goldburg, R.J., Hua, K., Nichols, P.D. (2009). Feeding aquaculture in an era of
finite resources. Proceedings of the National Academy of Sciences, 106(36), 15103-
15110.
Smith, A.D., Brown, C.J., Bulman, C.M., Fulton, E.A., Johnson, P., Kaplan, I.C., Lozano-
Montes, H., Mackinson, S., Marzloff, M., Shannon, L.J., Shin, Y.J. (2011). Impacts of
fishing low–trophic level species on marine ecosystems. Science, 333(6046), 1147-1150.
Tacon, A.G.J, Hasan, M.R., Subasinghe, R.P. (2006). FAO Fisheries Circular. No.1018; FAO
2010. FAO Fisheries and Aquaculture Report. No. 949.!
