Exploiting insects as feed for sustainable salmon farming - identifying the risks of pathogen transfer within the production chain

Isobel Swinscoea, David Olivera, Andre Gilburna, Robin Ørnsrudb, Richard Quilliama

Environmental Sustainability and Human Health Research Group, Biological and Environmental Sciences, University of Stirlinga

and the National Institute of Nutrition and Seafood Research (NIFES, Norway)b

isobel.swinscoe@stir.ac.uk, isobel.swinscoe@wordpress.com, @Isobel_Swinscoe

The global aquaculture industry relieson environmentally and economicallyunsustainable levels of wild fish catch, andgrain cultivation, to feed farmed fish.

Insects have long been reared on a relativelysmall scale to feed fish in less economicallydeveloped countries. However, massproduction of insects as feed for fish in the EUis currently limited because of the majorknowledge gaps relating to potentialpathogen contamination acquired from theenvironment (Figure 1), and whether thesepathogens pose a risk to the fish and,ultimately, to human consumers of the fish.

Traditional fish feed production is associatedwith significant greenhouse gas emissions andextensive land usage. By comparison, massinsect rearing produces a small carbonfootprint, can utilise organic waste streams asfeedstuff, and insect nutritional value for fishis at least equal to that of commercial feed.Marine macroalgae- both stranded onbeaches and cultivated- represents anabundant and cost-effective nutritious,organic waste material upon which theinsects could be sustainably reared. The useof macroalgae would also circumvent currentEU restrictions on feeding animal manure orfood waste to farmed insects.

The Aquafly project led by NIFES is exploringthe commercial feasibility of rearing the BlackSoldier Fly (Hermetia illucens) (BSF) and thekelp fly (Coelopidae) on marine macroalgaeand feeding the larvae to sustainably farmedAtlantic Salmon.

Figure 1. Potential mechanical and biological contamination of flies

Fly life cycle

Microbes on exoskeletons acquired from environment, including from fly vomit and faeces. Gut microflora acquired parentally and from food.

Contamination can come from the surface on

which eggs are laid.

BSF larvae can reduce

pathogens in feedstock, and kelp

fly larvae can suppress bacterial growth on seaweed,

but fly larvae can become contaminated by pathogens both internally and externally.

Few pathogens can survive Pupation but emerging adults will rapidly reacquire pathogens from their environment.

Harvest and process seaweed

Rear insects

Process larvae

Feed to fish

Humans consume fish

Public health risk?

Methods

• Pathogenic microorganisms can externally and internally colonisedifferent seaweed species to varying degrees, and seaweedprocessing techniques may eradicate only some pathogens.• The different biology and ecologies of BSF and kelp flies, combinedwith rearing techniques and strategies for processing of larvae intofish feed, may result in differential pathogen persistence duringmass insect production.• The results of this multi - stakeholder partnership will inform goodpractice guidelines for management of microbiological hazards in anovel feed production industry.

Predicted outcomes and conclusion

Harvesting of the seaweed and processing

it into insect feed in Ireland

Pathogen screening of harvested seaweed, and at

each processing stage

Production of a risk map for harvesting areas and

seaweed species

Rearing the flies on the seaweed, and harvesting

and processing the prepupae into fish feed in

the Netherlands

Microbiological sampling of each stage of process to

identify possible pathogen transmission modes

through insect life cycles, and environmental factors

facilitating pathogen survival

Feeding trials with Atlantic Salmon at

EWOS Research station, Norway.

Microbiological sampling of feed and fish to identify

their possible contamination via infected

insect larvae

Harvesting and processing of fish at GIFAS research

station, Norway

Sampling to assess pathogen presence in

microbial biofilms which can contaminate seafood

This research aims to identify andunderstand the potential risks ofenvironmental pathogen transfer andsurvival via the use of insects as feedingredients for sustainable salmonfarming.

Specifically, the objectives are:

1) To assess the extent to which the levelof seaweed contamination bypathogens is determined by seaweedspecies and the environment fromwhich the seaweed is sourced.

2) To understand how the methods usedto process the seaweed into insectfeed affects pathogen survival andtransfer.

3) To elucidate how insects mightfacilitate pathogen survival andincrease contamination within theproduction chain.

Aims

Adult Eggs

LarvaePupae

Introduction