Do fish vomit?

First written in October 2013. Guest blogger Lachy joins me to explore the fascinating world of fish. We wrote this piece for a science communication class.

Fish are friends, right? Yes they are. But unlike our human friends, we don’t know some basic things about them. So in order to get to know our aquatic acquaintances better, here’s three things we’ve wondered about recently.

1. Do fish vomit?

Inspired by this incredible Youtube video of cats puking to a techno soundtrack, we wondered, do fish vomit? With his usual “I know everything guys” approach, Lachy immediately claimed that vomiting is a function all vertebrates must have. Ellen, being skeptical of such a presumptuous claim, used her impressive googling skills to uncover the truth behind this piscine puzzle.

BLARGHARGHABLARG. Image by Maya/Flickr (CC BY-NC-SA 2.0).

BLARGHARGHABLARG. Image by Maya/Flickr (CC BY-NC-SA 2.0).

It turns out, fish can indeed upchuck their lunch. However, Lachy’s assertion that vomiting is a behaviour common to all vertebrates isn’t correct. Rats can’t spew!

2. What happens to fish in space? 

Image by Airport_Whiskey / Flickr (CC BY-NC 2.0).

Image by Airport_Whiskey / Flickr (CC BY-NC 2.0).

Living on Earth has its upsides. Literally. We (almost always) know which way is up or down. But in space, up or down doesn’t even exist! This can make life hard for creatures when they get sent to space by meddling astronauts. Lachy has seen a Youtube video of pigeons in zero gravity, and they really struggled. So what about fish in space? Would Dory be able to “just keep swimming?”

Hypothetically it could be very hard for fish. They stay upright in our oceans because of buoyancy: the force of gravity acts more strongly on the water around them than on themselves. So in space, they might just float around randomly, unable to control their movements or swim at all!

In 1973, this mystery was investigated in the Skylab. Two “mummichog” specimens were observed to dive incessantly, resulting in circular motions “as if stuck to the hands of a clock.” This phenomenon is called “looping.” But after a few days,  the mummichogs stopped such weird locomotion and began to swim normally, with their backs oriented towards the cabin’s light source.

3. Do fish feel pain?

If you’ve ever gone fishing, you’ve probably seen fish writhing as they are reeled from their watery homes, hook embedded in their mouth. Are these poor creatures in pain? Battles have raged in both the scientific literature and public court of opinion over whether fish can feel pain. But the most recent study, conducted by an interdisciplinary team of neurobiologists, fishery scientists and behavioural ecologists, concluded that fish do not feel pain the same way humans do.

Studies claiming fish can feel pain have relied on interpreting fish behaviour. But fish lack the part of the brain that perceives pain in humans, and administering painkillers, such as morphine, produces no effect on them. This suggests fish can’t feel pain, but either way it doesn’t make sense to decipher the meaning of fishy behaviour from a human perspective.