Everyone likes an underdog fish and, sure, animated features about anthropomorphized talking fish aren’t the proper place for cinéma vérité, but the entire premise of Finding Dory, the latest exercise in extreme competence from Pixar, is scientifically questionable. If this sort of piscine drama played out in real life, we might call the story Chum. Dory would make it about three minutes in open water before meeting a grisly end.
Dory is a Paracanthurus hepatus, what most snorkelers refer to as a Surgeonfish. Her species lives in reefs all over the Indo-Pacific, but they stick to reefs because they know what’s good for them. Reef fish are generally small and built to sprint over short distances and around obstacles. Placed in the open ocean, they’d fare about as well as a running back in the New York Marathon, which is to say that they’d make some headway but definitely lose ground to those better suited to go the distance. The problem is that the marathoners at sea, pelagic fish, are not only faster over distance — and often over short distances as well — but also a lot bigger and generally pretty hungry. Dory is in no way equipped to escape from or defend herself against pelagic fish, and thus would be snacked upon real quick.
Despite Finding Nemo’s attention to sharks (even the “fish are friends, not food” type), it would likely be a tuna (mahimahi, yellowtail, or skipjack) that would off our real-life protagonist. Though a hammerhead or blue shark shouldn’t be ruled out, those animals are more likely to attack schools of fish. As for Dory’s Whale Shark friend, she’d most likely pose little intentional threat. Whale Sharks eat fish even smaller than Paracanthurus hepatus. But they do slip up from time to time and, out in the open water, Dory has no natural defense mechanisms to draw on — nowhere to hide.
Dory’s also not really designed to dive deeper than around 130 feet, which means that in that Finding Nemo scene where they go all the way down to the deep ocean where this freaky-looking Black Seadevil hangs out should have also featured her lifeless body being eviscerated by sharp-toothed, blind deep sea predators.
Also, a big part of Dory’s diet is algae, which means she needs to live where there are things for algae to grow on or she’ll starve to death.
The moral of the story? Finding family is important, but doing dumbass things that will get you killed is a bad idea. Another solid message from Pixar!