Regarding intelligence and instinct divide I don’t subscribe to the idea that the two should be separated, to me intelligence is a function of instinct,
our knowledge is derived from our instinct to learn (or to “play” I suppose) and our application of those knowledge is functionally to satisfy certain instinctive goals.
Parrots as intelligent as they are, often fail mirror test (though they learn quickly afterward that it is just their own reflection) Archer fishes which see their own reflection in nature are going to perform much better than birds that mostly avoid standing water on the ground does that means Archerfish are smarter or just that their natural instinct is more suitable to such test ?
When it come to intelligence of non human animals I am not aware of any standardized definition so for now I am going with
“complexity of behavior and flexibility of certain behavior”
As in how many components are required for animals perform their natural behavior
And how many of those aspects can be modify to function under different context (or to take completely different behavior and use it for different purpose)
it is hardly a precise definition though I feel it is on the right track, for me animal intelligence (or rather my perception of it) is simply one of the aspect I factored in when deciding which animals I would like to keep or observe, maybe eventually scientist would come up with more precise definition.
Whether fishes can have emotions or not is much simpler, Fishes have mostly the same hormones or at least analog that induce the similar behavior, So fishes likelt can have emotions, Tetrapod are fishes as well and fishes are such a diverse group that is more different from each other as we are from them so I feels null hypothesis should be that as long as they have hormones and behavior induced by those hormones we could say they have emotion whether that is complex or not is different matter.
(Regarding prosocial hormones they share the same ones as birds do so if birds are emotional and social then fishes can be, although just because they can be doesn’t mean they are though maybe they are just using it for the original purpose of reducing water loss or other reasons, we need observation to prove that for each group of fishes)
