Dive Dry with Dr. Bill

#215: Holy Mackerel, Batman... Fish Farts

As an internationally respected scientist, marine educator and dive bum, I try to maintain a certain decorum in my columns. Yes, I realize I rarely succeed... but I do try, really! After reading the title of this column, I'm sure even some of my most devoted readers will question my sanity. You're not alone... so does my shrink. However, I am very serious about this week's subject (tee hee, ha ha). Let me explain.

I was recently diving Blue Car Wreck located below the road near Avalon's solid waste treatment plant. My pony bottle was in the shop for repairs, and I was diving with a mainland buddy, so I kept my dive fairly shallow... for me. With winter approaching, the sun went over the main ridge as we entered the water... making this a dusk dive. When the light is dim, it is a bit harder to make out subjects, so I was just cruising with the large schools of jack mackerel in the vicinity.

As I filmed a small group from one of the schools, I noticed something even in my tiny camcorder viewfinder! A stream of "tiny bubbles" was being emitted from one of the jack mackerel as it swam with the school. This caught my attention, and I watched the rest of the school more closely than usual. Yep, several of these baitfish released streams of bubbles. I was too late to capture them as they were released, but did film them as they rose to the surface.

When I got home and started editing the footage, I checked the first sequence very carefully. My suspicions appeared to be confirmed... the jack mackerel I caught on film (er, videotape) apparently was releasing a fish "fart!" OK, you all know I love to focus on munching and mating in my filming and my column. And even an amateur biologist (or regular human being) knows that munching can lead to farting... just as farting can lead to no mating. However, recent scientific findings in respected international journals have put an interesting twist on this "fascination."

Research by Canadian and British scientists published in the well respected journal Proceedings of the Royal Society of London revealed in 2004 that herring not only fart, but that it may serve a purpose heretofore unconsidered. I should add that the Royal Society chose to replace the word fart with another, more stately term (and many reporters preferred to use the phrase "breaking wind"). I'm not that stuffy! Herring may indeed use "breaking wind" as a form of communication to other fish in their "schools." This is definitely something that was strongly discouraged in my school. These scientists suggested it was the sound of "breaking wind" that was used to communicate. Unfortunately my camcorder in its underwater housing was not sensitive enough to detect any sound coming from the jack mackerel "breaking wind."

Prior to their research, the scientists were aware of a high pitched sound of uncertain origin that sounded like someone giving the "raspberries." It was through their work that they realized how it was created. The sound is a series of rapid ticks which they named Fast Repetitive Tick or FRT (hmmmm? just missing the "A"). It appears to occur primarily at night. WHAT they are communicating remains to be deciphered. It is believed that these high pitched sounds cannot be heard by fish predators like salmon, which could zero in on a meal otherwise.

As Paul Harvey used to say, now on to "the rest of the story." As it turns out, the release of gas by herring was noticed decades earlier by other scientists. The researchers involved in the 2004 paper (Wilson, Dill and Batty) apparently later decided that the release of air may nor have originated from the digestive tract and then passed out the anus. Instead they recognized that the air bladder, which keeps a fish neutrally buoyant, has a duct near the anus which may be used to vent gas from the air bladder as a fish changes depth. This is similar to the way a SCUBA diver will vent air from a BCD as they descend at the beginning of their dive, or ascend at the end.

Now I am pleased to say that this research was awarded an "Ig Noble Award" in 2004 by the journal Annals of Improbable Research. This publication, formerly known as the Journal of Irreproducible Results, annually selects research considered highly improbable... or highly amusing... and gives these awards just before the Nobel Prizes are awarded. I'm proud to say the ceremony took place in Sanders Theater at Harvard University where I slept through many an undergraduate lecture!

So perhaps my jack mackerel were not actually farting, but simply releasing excess gas from their swim bladders to maintain a steady depth. Now I must admit that I greatly prefer the first explanation to the second. We all know that "breaking wind" is the source of much humor in everyday life... and I think scientific research should be funny... er, I mean fun... wait, no I mean serious business. Go ahead... give me the raspberries!

© 2006 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles" or "Gentle Giants: Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Small school of jack mackerel, mackerel farting (in circle);
released gas drifting up towards the ocean surface.

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia