Not that it applies here, but there's an ecological evidence which is nothing short of a collection of anecdotes. Single observations or results from different sources are combined together to look for correlations between their common characteristics. For example, you search for all publications and reports on observations of intelligent behaviours in various fishes. Then you check if it's correlated with the brain size.
Oh and I had to add this, because it's about Jane Goodall: this kind of evidence is often used in ecological sciences and biology. She was one of those who came up with this approach when investigating the intelligence of non-human animals.