Maximising sustainable nutrient production from coupled fisheries-aquaculture systems

David F Willer,James P W Robinson,Karen Luyckx,Grace T Patterson,Semra Benzer

doi:10.1371/journal.pstr.0000005

Abstract

Aquaculture expansion is expected to meet growing demand for sustainable animal-source foods. Yet marine-fed species already require millions of tonnes of wild-caught fish for feed, over 90% of which are nutritious food-grade species. Allocating feed fish for human consumption could reduce pressure on marine resources while increasing seafood production. We examine micronutrient flows (the transfer of micronutrients from feed to fish) in Scotland’s farmed salmon industry, which is particularly reliant on marine feeds, to show that 1–49% of essential dietary minerals and fatty acids available in wild fish are retained in farmed salmon. Using three alternative production scenarios we show that reducing marine feeds in salmon production and allocating wild-caught feed fish for human consumption could produce more nutritious seafood and leave 66–82% of feed fish in the sea. Using global data on marine-fed aquaculture production, we show that removing wild-caught fish from salmonid production could leave 3.7 Mt fish in the sea while increasing global seafood production by 6.1 Mt.

Highlights

In this paper we demonstrate that marine-fed farmed salmon is an inefficient way to produce nutritious seafood, and that directing wild-caught ‘feed’ fish towards human consumption could maximise nutrient production while relieving pressure on fisheries stocks
We compile the latest publicly available data on fishmeal and fish oil (FMFO) inputs from wild-caught fish used in farmed Scottish salmon production, taking the form of FMFO composition data from 2014 (Fig 1)
Worldwide salmon production takes 60% of all fish oil and 23% of all fishmeal used in aquaculture [28], yet salmon only makes up 4.5% of global aquaculture production by volume [1]

Summary

Introduction

Growth in aquaculture is crucial to meet global animal-source food demands [1–3]. Our ability to increase production of land-derived foods is increasingly limited by scarce land and water resources [3], fish and seafood are rich in bioavailable nutrients not found in plantbased foods [2], and there are opportunities for aquaculture to provide all of the 177 Mt of additional animal-source food needed worldwide by 2050 [3]. Aquaculture can provide a lowcarbon, sustainable, affordable substitute for terrestrial meat sources, and demand is expected to continue to grow quickly [4–6]. With a large proportion of production—70% in 2018 [1] —reliant upon external sources of feed, further growth in fed aquaculture is unsustainable [7,8]. Fishmeal and fish oil are key components of fed aquaculture, comprising 76% and 71% of global resources used in aquafeeds, respectively [9]. There is an urgent need to optimise resource allocation in aquaculture [11,12]

Methods

Results

Discussion

Conclusion