NEWS • 2020-11-12
Healthy aquaculture for people and environment
“Fish is good for you”, parents tell their children, and while it is true that seafood is healthy, it is also true that just how nourishing it is varies considerably between species. People in many low-income countries are particularly dependent on seafood for their nutrition, so when overfishing diminish fish landings, these people are the most affected. Aquaculture is a way to meet local demand, but besides its environmental impacts, farmed seafood generally contains less valuable micronutrients than wild-caught fish. A new study published in Nature Food shows how aquaculture systems in Bangladesh can improve both nutritional content and environmental impact.
Although food security in Bangladesh has been improving in past decades, it continues to be a major public health concern, and as fish consumption in the country has shifted from wild-caught to farmed fish, the intake of key micronutrients has deteriorated. While the protein levels are similar, wild-caught seafood provide significantly higher levels of zink, iron, calcium and vitamin A, nutrients important for instance for the immune system, bone structure and cognitive development.
To see if there is a way to change this, the researchers, led by former Beijer Young Scholar Alon Shepon (Tel Aviv University), and including Beijer researcher Patrik Henriksson (also at Stockholm Resilience Centre), examined the combination of species of 14 types of aquaculture systems in Bangladesh and whether nutrient supply could be improved..
Finding the best fish and farming methods
A recent life cycle assessment (LCA) study of aquaculture systems in Bangladesh, led by Patrik Henriksson, and extensive research on the nutritional benefits of fisheries provided rich data sets to build on to explore solutions that benefit both the environment, concerning problems related to global warming, land use, freshwater consumption, eutrophication, acidification and freshwater ecotoxicity, as well as human health.
Of the twelve fish types farmed in these aquaculture systems, only one group had better nutritional values than wild-caught fish, the team found. This is a group of small indigenous fish species (SIS) that currently constitutes a very small share of the farmed fish. The researchers calculated that increasing the proportion of this fish group to 30%-50% of total production can leverage the nutritional densities of production to equal that of wild caught fish.
“These SIS are fatty fishes with a better nutrition profile than lean fish. They are also eaten whole, which means that all the valuable micronutrients, such as in for instance calcium in the bones and vitamin A in the heads, are not wasted”, Patrik Henriksson explains.
They also found that from an environmental perspective, aquaculture systems that combine seafood farming with growing rice, is the best system to minimize environmental harm. This is good news, since rice production and consumption in Bangladesh is widespread, integrating fish production into existing rice systems can be carried out with few interventions and investments. Moreover, the integration of aquaculture with agriculture avoids the expansion of food production into pristine habitats and increases the profit margins for farmers.
More is more when choosing species
Subsequently, as so often is the case with sustainable solutions, polyculture production systems are preferred over monocultures for several reasons. First, systems that culture different types of food can provide greater nutrition over a range of nutrients, reducing the risk of malnutrition. Moreover, polyculture systems are usually more resilient, they reduce the risk of economic loss from price fluctuations and disease outbreaks, and in many cases improve environmental performance.
Seeking solutions that people can accept
There are good reasons to target the aquaculture industry in Bangladesh to improve human and ecosystem health the authors claim:
“As fish are culturally accepted across all socioeconomic groups in Bangladesh, aligning food choices with best nutritional and environmental practices does not require drastic changes in consumption patterns, hence our results are easily acceptable from both policy and consumer standpoints.”
However, there are some obstacles for this transition as Patrik Henriksson points out:
“The economic forces favour species with both poorer environmental performance and nutrient content, such as shrimp and pangasius. Producers and authorities therefore need to try to find added value for the more nutritious indigenous species we point to in our study, in order to render them the economic value they deserve.”
Shepon, A., J. A. Gephart, P. J. G. Henriksson, R. Jones, K. Murshed-e-Jahan, G. Eshel and C. D. Golden . 2020. Reorientation of aquaculture production systems can reduce environmental impacts and improve nutrition security in Bangladesh. Nature Food (1):640–647.