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Study Reveals Plant Ingredients are not Sustainable Fishmeal Substitutes

Commercial fish feed manufacturers are progressively switching fishmeal – a powder made from fish – for crop-based ingredients in a move compelled by economic incentives and a desire to enhance the sustainability of aquafeed.

Wesley Malcorps, of the University of Stirling, studied the impact of substituting fishmeal with plant ingredients in shrimp feeds. (Image credit: University of Stirling’s Institute of Aquaculture)

While this method is commonly recognized as being more environmentally friendly, the new research – led by PhD researcher Wesley Malcorps, from the University of Stirling’s Institute of Aquaculture – challenges this prevalent theory.

The multidisciplinary team investigated the trade-offs between terrestrial and marine resources as a result of implementing this common practice in shrimp feeds. The scientists concentrated on the shrimp business, as it is one of the leading consumers of fishmeal in the aquaculture sector.

The study learned that the switching of fishmeal with plant ingredients simply moved pressures from limited marine resources to land-based food production systems, with environmental consequences. The professionals involved in the work are currently calling for a “paradigm shift” in thinking around the relative sustainability of aquafeed ingredients.

Substituting fishmeal for plant ingredients is considered by many to be environmentally sustainable, as it reduces dependency on finite marine resources. However, this would shift resource demand from the oceans onto the land, potentially adding pressure to the land-based food production systems, which are already under pressure to meet global demand for food, feed, biofuels, and bio-based materials. In turn, this would affect the environment and biodiversity, as well as the availability and prices of crops. In addition, the nutritional requirements of certain aquatic species may limit the amount of fishmeal substitution due to essential nutrients, which are variable or imbalanced in terrestrial plant ingredients. Furthermore, increased inclusion of plant ingredients in aquafeed could also affect the nutritional value of farmed seafood.

Wesley Malcorps, PhD researcher, Institute of Aquaculture, University of Stirling.

Fishmeal is produced mainly from small pelagic fish, as well as fish processing waste. At present, the waste element constitutes, on average, between 25 and 35% of the product; however, this portion is on the increase.

During the last few years, in reaction to fishmeal price rise, the product has been progressively switched for plant ingredients. In 2000, 19-40% fishmeal was included in shrimp feed, however, that dropped to 11-23% in 2014.

The research modeled incremental fishmeal substitution, from 20-30% to zero, by plant constituents – such as soybean meal concentrate, pea protein concentrate, rapeseed meal concentrate, and corn gluten meal – which are commonly included in current feeds for the two main shrimp species produced worldwide, black tiger shrimp (Penaeus monodon) and whiteleg shrimp (Litopenaeus vannamei).

The team then evaluated the impact this could have on terrestrial and marine resources, such as freshwater, fish, nitrogen, land, and phosphorus.

The study exposed that total substitution of 20-30% of fishmeal totals – subject to the species – could result in an increasing demand for freshwater, of up to 63%; land, of up to 81%; and phosphorus, of up to 83%.

These are significant increases, as only a small proportion of the feed is actually substituted. Our findings suggest this approach would lead to additional pressures on essential agricultural resources, with associated socio-economic and environmental effects as a trade-off to pressures on finite marine resources. It could lead to competition for land and other terrestrial resources, causing social and environmental conflicts that, in turn, may affect the resilience of the global food system.

Wesley Malcorps, PhD researcher, Institute of Aquaculture, University of Stirling.

Aquafeed usually utilizes only a small percentage of universal crop production, however, with aquaculture one of the fastest expanding food sectors, the experts warn extra pressures on vital terrestrial resources “may become more obvious” in the future.

Paradigm shift

Our model highlights the need for a paradigm shift in the definition of sustainable shrimp feed. Additionally, the model may be equally applicable to other intensively farmed species with similar scenarios of marine and terrestrial feed ingredient requirements. An excessive dependency on the use of plant ingredients for aquaculture could lead to deleterious effects on the environment and indirectly impact human health by altering the nutritional value of the aquaculture products.

Wesley Malcorps, PhD researcher, Institute of Aquaculture, University of Stirling.

Mr Malcorps proposes finding an “optimal balance” between terrestrial and marine resources in aquafeed; deliberately include superior quality fishmeal; enhancing the use of fish by-products and food waste in feeds; and exploring the potential for unique ingredients – such as algae, microbial biomass, and insect meals – to be included.

The multidisciplinary team included industry and academic professionals from around the world, including: MatureDevelopment BV (Netherlands); Research Institute for Agriculture, Fisheries and Food (Belgium); Mexico Aquaculture Research Inc; Association of International Seafood Professionals (Australia); Aquaculture without Frontiers (USA); Universidad Tecnológica del Mar de Tamaulipas (Mexico); IFFO, The Marine Ingredients Organisation (UK); Utrecht University (Netherlands); University of Zürich (Switzerland); and Harper Adams University (UK).

The research paper titled, “The Sustainability Conundrum of Fishmeal Substitution by Plant Ingredients in Shrimp Feeds”, has been published in Sustainability.

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