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Aquaculture and Sustainability
Where is the rapidly expanding aquaculture sector heading? Out of the 462 identified species available for cultivation, only 20 species account for 70 percent of the total global volumes of farmed fish and shellfish. Besides making you wonder what you are missing out on in terms of healthy and culinary discoveries, this may have implications for the industry’s long-term sustainability. The current diversity has actually not been properly mapped out, and if you do not know where you stand, it is hard to know where to go.
In a new study in Reviews in Aquaculture, centre researcher Max Troell and colleagues develops a method for quantifying and mapping species diversity in the global aquaculture industry.
Establishing a benchmark is needed given the rapid expansion of aquaculture and the increased calls for diversification as part of strategies to sustainably grow the sector. Our results can be used to inform policy development and technological innovation.
Max Troell, co-author
The researchers collected statistics from the UN Food and Agriculture Organization (FAO) and applied a diversity index popular in ecology to measure the species diversity in different countries. They looked both at number of species and the spread of these species in the overall production, that is, if one or few species dominates the production. Not so surprisingly they found that nine of the ten most diverse aquaculture productions are found in Asia with China in the very top of the list.
"An important but troublesome finding was that of the 74 million tonnes of farmed seafood almost a third was not classified down to species level – something that could have implications for sustainability," argues Marc Metian, lead author of the study.
Currently, there is a trend towards more species being cultivated, however, very few ‘new’ introductions last more than a couple of years. Almost one quarter of all the species farmed since the 1950s have been in production for five years or less. Failure to introduce new species are often due to premature attempts to scale up or misjudgement of the market demand. The recipe for success in the aquaculture industry has instead been to focus on either nutritionally superior species or low cost fast-growing species that are well-known and in demand by consumers.
"Focusing on fewer species have meant higher productivity and profitability in the short-term, for better or worse in terms of environmental sustainability in the long-term," says Metian.
FAO and other international organizations are calling for diversification in order to improve the sustainability record of the sector.
The study by Troell and his colleagues found that higher diversity generally means higher production and a better outlook for long-term profitability. Productions that rely on one or a few species are more exposed to changes in market demand and environmental conditions.
For instance, the Chilean salmon industry have long struggled with infectious disease outbreaks, at times bringing the production to a near full stop. This vulnerability to unforeseen events is all the bigger of a problem if the country or region in question is heavily dependent on single-specie aquaculture sector.
So how can aquaculture be diversified? To increase species diversity by introducing non-native species is a risky strategy as non-indigenous species poses a threat to wild fish populations.
Much aquaculture is still in the form of open-net pens and land based ponds and farmed fish can, and do, escape. Other options are to cultivate previously unused native species or to genetically improve species. Today, it is estimated that only 10% of the global production is based on genetically improved individuals.
Diversification on the genetic level can be achieved through traditional selective breeding or genetic modification (e.g., the latter exemplified by the recently introduced AquaBounty salmon which is genetically engineered to grow faster).
The researchers advocate for a mixed box of tools to diversify global aquaculture. Policies are needed on both national and international level have the industry ‘de-specializing’ their business models. Policy should support the development and sharing of technologies, material equipment, and fish farming skills. In addition, we consumers might need an educational push to explore new species.
China stood out in the analysis; the country not only has the highest aquaculture production but also cultivates the highest number of species in the most diverse production systems. This is no great surprise given China’s long history of aquaculture and natural abundance of species and sites suitable for fish farming.
“Importantly, species diversity has also been a major goal of the Chinese government’s aquaculture development programmes”, explains Troell.
Similar strategies have been employed by other fish producing Asian countries, and in several instances the diversification have provided socioeconomic benefits to small-scale farmers. China is a case in point.
The researchers applied the Shannon Diversity Index onto the most recent FAO statistics. The Shannon Diversity Index measures species diversity (i.e., number of species) and evenness (i.e., how these species are distributed in the total population of farmed fish and shellfish). There are several challenges with attempting to accurately access the diversity in the global aquaculture; data is often lacking or of poor quality due to misreporting on country level. Across countries, there are variations in how species are classified and some productive operations are not captured by national statistics (e.g., backyard farming). In addition, in 2017, 34 percent of total production was in the so called “not elsewhere indicated” (nei) category. These are farmed organisms that have not been ascribed to a specific specie category. This group covers many taxonomic levels and may limit the analysis of species diversity due to overlaps and gaps in the species count.
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