What about flash frozen?
.
cooked at low temperatures
I sous vide fish at 135F.
I’ve not found any studies whatsoever on instability of DHA/EPA at low temperatures, only marked structural changes (including unhealthy ones) at high temperatures, including prolonged temperature exposures.
Frankly, the mere question alone would prompt my own investigation if I had a laboratory since I’ve never cooked fish in that manner. My only concern is the lengthy cook time. Poaching achieves the same result with, IMHO, minimal loss. Likewise with low temperature baking (filets, rather than steaks) until ‘just done’.
But those results are solely anecdotal based upon my personal experience: The years-long course of health recovery mandated that I become a literal lab rat, one result being repeatable with tangible health benefits via consumption as-described vs. supplements & prior ignorant methods.