Since I haven't seen anything regarding this I'm gonna share another useful tip:

I know the filled fishbasket is a nuisance with both weight and the need to refresh it once in a while. What you can do is after you've caught a fish, throw it out again, cryo it and you can preserve it this way as long as you like. Just craft some more baskets when you are going to tame a shadowmane just bring out the fish from your cryopod, use baskets to fill it up again and then use them on the shadowmane. Up soother ppl can see it too