Mental Floss

2 Odd Things I Just Learned About Fish

Matt Soniak

When I'm not blogging for mental_floss, I can usually be found wearing bright orange rubber pants and gutting, cutting and selling fish at the local Whole Foods. Sometimes, these two worlds collide and I find some scientific research involving my finned friends that needs blogging about. Recently I learned two things about fish that may seem like throwaway trivia at first, but provide us with some useful information once you get past the "gee-whiz" stage. (Note: That's not me in the photo. But it is Charlize Theron. Picture courtesy of Hollywood Back Wash.)

1. Odd thing I learned #1:
Vulnerability to being caught by fishermen is a heritable trait in largemouth bass
After tracking catches during four years of experimental fishing, researchers at the University of Illinois segregated largemouth bass in a lake into groups of high and low vulnerability (HV and LV groups, respectively) to being caught. The offspring of these two groups were reared, tracked and segregated into HV and LV groups. Their offspring, the third generation of fish in the experiment, went through the same process (there's a slightly more detailed explanation of the study at my website). The researchers recently published the results of the 20-year experiment* and conclude that, one, vulnerability to being caught by fishermen is a heritable trait in the bass, and two, recreational fishing can cause evolutionary changes the same way commercial fishing can.

The takeaway:

Male largemouth bass are single dads, staying with the eggs and guarding their offspring for the first month after they hatch (the females leave the eggs after laying them). Aggressive HV males have more success mating and are great dads, protecting their fry from predators, but they're also more likely to go after fishermen's lures, get caught and leave their offspring vulnerable to predators. The combination of the bass' reproductive strategies and the pressure of recreational fishing during spawning season may affect the bass' reproductive success and continuation, so the researchers recommend that wildlife management agencies create bass spawning sanctuaries and limit or restrict bass fishing during spawning season.

Odd thing I learned #2:
Fish get seasick
German zoologist Reinhold Hilbig put an aquarium containing 49 fish on a plane, which, during its flight, went into a steep dive to simulating the loss of gravity. Eight of the fish began turning around in circles, and exhibited other signs of having lost their orientation and sense of balance. Hilbig told the Telegraph that the fish behaved "like humans who get seasick," and "looked as if they were about to vomit." (What that looks like I don't know.)

The takeaway: This was an experiment on the effects of weightlessness in water as part of Hilbig's research on how humans are affected in space. The eight seasick fish were later killed and their brains were examined, revealing that many of them had asymmetric inner ears. Some fish have an inner ear system that helps them stay upright, like the inner ear balance system in humans. Asymmetric inner ears in humans, and apparently, fish, make one more susceptible to motion sickness. Hilbig hopes to use the results of the experiment to draw conclusions about how humans might react in similar situations. (That's sort of vague, I know. I wish there were more, but the news stories on this are all short on info and no amount of Googling seems to turn up the name of a paper associated with the study or even background info on Hilbig. Alas.)

*Philipp, David P., Cooke, Steven J., Claussen, Julie E., Koppelman, Jeffrey B., Suski, Cory D., Burkett, Dale P. Selection for Vulnerability to Angling in Largemouth Bass. Transactions of the American Fisheries Society 2009;138:189"“199. DOI: 10.1577/T06-243.1