What the Heck is an Otolith?

One of the many posts I have made about my fishing adventures on my Urban Fly Fishing DFW Facebook page was a photo of a freshwater drum (Aplodinotus grunniens) I had caught. This fish is known by many names, with a local favorite being “gaspergou” (GAS-per-goo), which is a corruption of the Cajun/Creole French casse-burgot, roughly meaning “mussel breaker.” Mussels and other mollusks comprise a substantial part of the freshwater drum’s diet, so the name makes perfect sense. If you speak Cajun/Creole French.

Of course, there was the normal discussion on the page about where I caught the beast, what fly did I use, are they hard fighters, are they good to eat, etc., but one guy chimed in out of left field with something along the lines of “Those are the fish with pearls in their head, right?”

Huh?

I literally cocked my head to one side and read it again. I had never heard of such a thing. Pearls in the head of a fish? I had to know more.

I was instantly on a Google quest, and searching for “freshwater drum head pearls” yielded some interesting results. These “head pearls” are actually bones in the head of the fish called otoliths that enable the fish to sense both direction and orientation in the water, and operate much like the bones of the inner ear in humans. In fact, the word otolith literally translates to “ear stone.”

As it turns out, the freshwater drum has some of the largest otoliths of all freshwater fish. Analysis of the structural and mineral content of these bones can tell us things such as the age of the fish and the climate and location in which the fish grew. Otoliths are also part of the fossil record dating back at least 150 million years. Present day, these relatively durable fish bones can be found along the edges of lakes and rivers inhabited by freshwater drum.

But the most interesting thing about otoliths (to me, at least) is their cultural history. These bones have been collected for millennia by Native Americans and used as good luck charms, currency, and jewelry. One of the colloquial expressions for these head pearls is “lucky stones.” Folklore suggests that carrying one or more of these lucky stones in your pocket, perhaps stitched into a small chamois leather or flannel pouch with coins, incense, pepper, perfume, or other items to increase their power, will imbue the holder with good luck. And according to this folklore, the people most likely to benefit from this good luck are job seekers, gamblers, businessmen, and prostitutes.

In keeping with the musical theme of Urban Fly Fishing Dallas–-Fort Worth, there’s even a song about lucky stones, recorded by blues legend Gertrude “Ma” Rainey in 1924 entitled Lucky Rock Blues.

SOURCES:
Lucky Mojo Curio Company
wikipedia.org
NeoNaturalist.com
fisheries.noaa.gov