Elise Chalcraft

Tasting before wasting

Optimizing our African Catfish feed

My project for the past 8 weeks has been to look at how we could use waste streams from both the aquaponics greenhouse and the kitchen to feed our catfish to make the system as circular as possible. Fish feed is one of the three largest inputs currently for aquaponics systems, the other two being water and electricity inputs (Love et al., 2014; in Robaina et al., 2019).

I have been experimenting with feeding various plants to the catfish and documenting their reactions to the change in diet.

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Aquaponics plants as fish food try-outs - Using aquaponics waste streams as potential fish feed alternatives These were the fish feed alternatives used in my 8 week experiment with using waste streams at MediaMatic to close the fish feed input in our semi-closed aquaponics system.  Elise Chalcraft

But why bother?

Let’s start with some fun facts about the current situation:

  • Global population numbers expected to increase between 20% and 30% by 2050 (Calone et al., 2019).
  • 60% of fish feed production is held by the top 10 producing countries which means that key ingredients traditionally used within feed formulas are internationally traded commodities and therefore subject to global market volatility and rising prices (Robaina et al., 2019).
  • Three million additional tons of fish feed will be needed to sustain current aquaculture growth rates annually by 2030, along with the 70% price increase of fish oil which is essential ingredient in current fish feed production (Robaina et al., 2019).
  • Protein within fish feed is mostly imported (Smárason et al., 2019) which is not only expensive but the supply is also based upon over-exploitation of natural resources (Raji et al., 2018).

With these facts in mind, it seems like a good option to look into other local and alternative feeding options…

 

Flying fish: their diet of poultry proteins

The current fish feed used contains fishmeal, fish oils, and proteins derived from poultry (Skretting, 2021) which are internationally transported and not naturally found in African catfishes diets (poultry).

As seen in previous experiments in the Aquaponics Greenhouse, using local protein sources such as black solider flies is a good alternative but not economically viable long-term.

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Black Soldier flies - pre-pupae, pupae, flies different states in the live of a Black Soldier Fly pre-pupae, pupae, flies Amy Claire Elizabeth Galbraith

Vegan option for the vegan restaurant?

There are vegan catfish fish food where the proteins are plant based including: dried dandelions, soy bean, parsley, corn, garlic, sage, coconut, horseradish and even juniper berries! (Sawyer, 2015).

Whilst these plant-based proteins seem like a sustainably sound solution, we must make sure to look at all aspects of them such as soil degradation processes, water usage, and transportation.

It also seems silly to grow these crops only for them to be mashed up to be used for the fish, therefore using agricultural waste streams which include these ingredients would solve this problem for the time being.

 

Follow along for further research and insight into fish feed territory!

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fish feed comparison glasses - the different kind of feed we're using at mediamatic

References:

Calone, R., Pennisi, G., Morgenstern, R., Sanyé-Mengual, E., Lorleberg, W., Dapprich, P., Winkler, P., Orsini, F. and Gianquinto, G. (2019). Improving water management in European catfish recirculating aquaculture systems through catfish-lettuce aquaponics. Science of The Total Environment, [online] 687, pp.759–767. Available at: https://www.sciencedirect.com/science/article/pii/S004896971932738X [Accessed 21 Apr. 2021].

Raji, A.A., Alaba, P.A., Yusuf, H., Abu Bakar, N.H., Mohd Taufek, N., Muin, H., Alias, Z., Milow, P. and Abdul Razak, S. (2018). Fishmeal replacement with Spirulina Platensis and Chlorella vulgaris in African catfish (Clarias gariepinus) diet: Effect on antioxidant enzyme activities and haematological parameters. Research in Veterinary Science, [online] 119, pp.67–75.

Robaina, L., Pirhonen, J., Mente, E., Sánchez, J. and Goosen, N. (2019). Fish diets in aquaponics. Aquaponics Food Production Systems, pp. 333-352. Springer, Cham.

Sawyer, J. (2015). AquaOrganic Fish Feed. [online] The Aquaponic Source. Available at: https://www.theaquaponicsource.com/shop/fish-care/fish-food/aquaorganic-fish-feed/ [Accessed 15 Jun. 2021].

Smárason, B.Ö., Alriksson, B. and Jóhannsson, R. (2019). Safe and sustainable protein sources from the forest industry–The case of fish feed. Trends in Food Science & Technology84, pp.12-14.

Skretting. 2021. Innovative feed solutions for fish and shrimp - Skretting. [online] Available at: https://www.skretting.com/en-us/feed-and-services-for-aquaculture/?filter=Species.eq.Catfish&page=1&page_size=10. [Accessed 23 April 2021].