I am not an expert, but in terms of phraseology I can see the concern: given the use of "fish" and other more specific words for squid, krill, etc, I would assume "animal protein of marine origin" to mean "non-fish animal of marine origin."
But, looking into it, I assume the difference in phrasing is a specific product patent issue, and that ingredient has been labeled and patented as such specifically. In which case it would be a shorthand for a particular combination of ingredients.
Here is a patent for "Hydrolysates of animal proteins of marine origin" that may not be the exact same thing, but here's its breakdown:
"These hydrolysates are prepared from a protein source selected from mackerel, salmon, green crab and white fish, and at least 70% (preferentially at least 80%) of the total weight of peptides of these hydrolysates correspond to peptides having a molecular weight of less than 1000 Da."
Whether shark or other questionable ingredients are included in the food you're looking at, I couldn't say. A company not emailing back, though, is not comforting.