I'm almost ready to give up fish, as I gave up birds and mammals long ago. Fish is going to be a very difficult texture to replace.

Another alternative is insect protein which I am in big favour of. Mealworms for example make great meatless burgers:

https://www.wur.nl/en/project/insects-as-food-ingredients.ht...

I've happily eaten insects as a regular meal in the americas and other countries, and see it only as a cultural barrier for it to be introduced large scale in western markets.