Tasmiyyah On Fish
One way of understanding this point in Quran is to combine the negative and positive directions that would read something like “do nit mention names of false gods while slaughtering animals and (if you have to, better) mention Allah’s name (as He deserves it far more than the false gods). The other way to understand it to keep them separate and that would mean that the 6:118 verse is for pronouncing God’s name before eating anything and not (only) slaughtering animals. The bible supports this view as it requires mentioning of God’s name after eating but no requirement of tasmiyyah while slaughtering animals. In view of that the safest view would be to say God’d name while eating food no matter its meat fish or veggies. … “When you have eaten and are satisfied, bless (praise) the Lord your God for the good land He has given you.” … (Deuteronomy 8:10)
I agree if we read 6:118 -121 it’s clear we are not supposed to eat anything upon which God’s name has not been pronounced. I couldn’t find anything that would restrict it to slaughter meat only. This sounds more of a principle rather than a practice. If we restrict the application of this verse to meat it wont solve the question of fishing without tasmiyyah. If we take it as a principle applicable to all what we eat it solves all problems. When we say bismillah before eating, technically Allah’s name “has been pronounced”. Meaning no matter who pronounce Allah’s name as long as someone has done it we can eat it. This makes sense in case kids who have not learned to speak yet but need to be fed. Old people may not be able to speak sometimes but need to be fed by a caregiver.