Fishy Business
Fish have long delivered fertility to the soil, via both natural and human-driven processes. Soil food webbers use fish byproducts to increase fungi in compost piles (those of us without wildlife pressure) and – more often – to increase fungal biomass in compost teas. But these days, sourcing commercial fish products raises some serious ethical questions. What are the ecological consequences related to where the fish came from and how it was caught? Christina Cook of the Organic Gardener’s Pantry in Victoria recently wrote an excellent overview of the dilemma (see https://www.gardenerspantry.ca/blogs/news/where-have-all-the-fishes-gone).
One way to steer clear of supporting destructive ecological practices is to make your own fish amendment. It is important to understand the two different products on the market when you are trying to create an effective do-it-yourself version. Fish hydrolysate is what you are looking for if the goal is to increase fungal biomass. Commercial fish hydrolysate is enzymatically cold processed, keeping all the oily bits intact (it is these complex molecules that the fungi so love to break down and feast upon). Commercial fish emulsion, which has had the oils removed and has been heat-treated, will feed bacteria. After years of microscopically analyzing soils in the valley I can confidently tell you that increasing fungi, not bacteria, is what we need to be focusing on!
The first step to making your own fish hydrolysate is to source the fish ethically by either catching it yourself, knowing the person who caught it responsibly, or through something like the Michele Rose Community Supported Fishery in Cowichan Bay. You will need all of the filleted raw carcass, or at very least the raw skin and some meat, ensuring you have the oily bits. Chop roughly, put through a blender (thrift store shopping trip, anyone?), strain if you like, and freeze in ice-cube trays. No enzymes or anti-microbial preservatives required! Thaw and dilute as needed. Use very little in compost teas or for feeding your plants.
So if you come across some ethically caught raw fish carcasses during your summer adventures – even if you just freeze and deal with them later – I encourage you to put them to very good purpose. Or offer to a gardener friend. Long live fungi!
