As the biodiversity of fish species declines for a variety of reasons, ranging from toxic runoff to overfishing, researchers find that biomass compensation can harm the health of populations that depend on these fish for daily food intake.
Fish. Photo credit: Foxys Forest Manufacture / Shutterstock.com
The global decline in fish biodiversity
It is estimated that around 2 billion people around the world rely on wild-caught or harvested species such as fish, insects, fruits and other non-agricultural foods for their nutritional needs. Of these, fish are the most common and important wild food, as they are often rich in protein, zinc, iron, calcium and omega-3 fatty acids.
In the past few decades, various factors have resulted in the biodiversity of wild fish changing significantly. Some of these factors are overfishing, pollution, climate change and habitat degradation. Despite these changes in fish biodiversity, the fishery remains steadfastly supplied with fish, as small and fast-growing species often offset the decline in more vulnerable fish species.
How can a decline in fish biodiversity affect human nutrition?
While these fish species are more tolerant of these biodiversity changes, they often differ significantly in their nutritional content, which can have an impact on the health of people living in areas that rely primarily on fish for their nutrient uptake. In a recent Science Advances study, researchers from Columbia University in New York, NY, wanted to understand how this decline in wild fish biodiversity may affect the nutritional status of those who consume these fish.
In their work, the researchers studied people who live in the rural area of Loreto, a division of the Peruvian Amazon. For this population of approximately 800,000 people, the people of Loreto rely heavily on wild fish species for much of their daily nutrients.
Unfortunately, both the increase in local hydropower development and soil erosion and continued overfishing have significantly reduced the biodiversity of their freshwater fish population. It is estimated that the residents of Loreto consume fish at least once a day for a total of around 52 kilograms of fish per year. Despite this reduction in fish diversity, the number of fish available to fishermen in Loreto has remained sustainable for the local population.
To understand how declining fish biodiversity can affect the nutritional status of locals, Columbia University researchers first looked at how many people in Loreto met their Annual Reference Nutrient Intake (RNI) for the seven essential animal nutrients. These nutrients include protein, iron, zinc, calcium and the three omega-3 fatty acids linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
In the absence of biomass compensation, the researchers predicted that an average of 1.76% of all nutrients would result in a loss for the local population. In particular, when the current fish supply was replaced by smaller and less trophic fish, the nutrient supply changed significantly, especially the protein and calcium supply. While this may be true, replacing large-bodied and migratory species with smaller, sedentary, low-trophic species could actually improve nutrient uptake, as the smaller species have been found to provide more of the three omega-3s Compared to the larger fish.
Future effects of decreased fish biodiversity
Overall, the results of the current study were not purely hypothetical, as many of the stimulated changes in biodiversity were reported in many Amazon and other tropical inland fish communities. While the ability to predict the future of fish biodiversity in the Amazon is not easy, ongoing projects that continue to threaten fish biodiversity are likely to continue to transform the food intake of local people.
As with any other complex system, a compromise has been found. Some things go up while others go down. But that only lasts up to a point. “
While some potential pros and cons of biomass compensation have been identified, the researchers believe that the extinction or loss of 40 species of fish could significantly reduce the food intake of the remaining species available for consumption.
- Heilpern, SA, DeFries, R., Fiorella, K. et al. (2021). The decreasing diversity of wild-caught species is threatening the nutrient supply of food. Advances in Science 7 (22). doi: 10.1126 / sciadv.abf9967.