Or can you truly be a vegan on this diet? If necessary, which fish in particular is absolutely necessary and exactly how much?
I think it’s ok not to if you are getting enough of the good things (that can be found in fish.)
These I believe are protein and omega3.
You would have to eat a lot of the plant based equivalent to achieve what a small amount of fish does.
The fish to Achieve obtaining the health benniefts from are Salmon, mackerel, sardines etc oily fish for their omega 3 but go easy on the tuna due to the possible mercury build up. ( I have have it just once a week. )
Other fish are great too I’d recommend for you is Snapper ( it’s less fishy than other fish )
I’m not sure we all have the same kind of fish in their country though.
( btw I bake it in the oven and like it with chutney )
Hope you can stomach trying some.
Salmon is definite one I’d try first. ( just a small amount as it’s quite rich ) goes well in wraps, with rice on crackers etc.
Others may have more to add as I’m reciting from memory I may have missed some points.
Good luck.