I am using a home made version of fish hydrolysate produced by first culturing a liquid EM and using that to ferment saltwater fish waste with added sugar. The result contains both the bacteria, sea minerals from fish and the usual NPK found in fish hydrolysate, approx 3-2-1. It took about 3-4 months using 200 lbs sugar, whey from 5 gallons milk, an EM starter culture, and 200 lbs fish guts/heads/etc from the local market (traded for mangoes).
Smell is fishy but sweet/sour, not the smell of rotten fish you might expect, there is some fish oil.
Yield was 40 gallons strained emulsion plus 20 gallons leftover bones and scales.
Cost was low and has been working well as soil drench and foliar, one cup with 5 gallons water.
I am considering adding ground papaya as a pre-digestion stage in my next batch.