I agree with @Senior Sea Kayaker on all counts.
Standard guidance for preserving fish and seafood requires pressure canning, even when starting with cooked items.
I think you could get a similar result by following this recipe, then heating the sealed jars in a sous vide set-up, storing in the fridge and consuming within a week or two.
I used 90 min @ 45°C (113°F) for 250 ml jars of tuna confit*. The fish was first brined, then packed in oil with seasonings and ended up nicely flavored from the herbs and spices in the oil so I think something shorter/hotter like that might be a good substitute for that 4-6 week aging time in that recipe.
* Just edited the time & temp. I got those values from a ChefSteps recipe. Modernist Cuisine at Home uses an hour @ 50°C in 500 ml jars.
I used a recipe for tuna confit from the Zuni Cafe Cookbook where she does the heating process on the stovetop over very low heat and adapted it for sous vide. You could go the stovetop route as well, though I’d advise the use of a functional thermometer.
