Still experiencing tech issues, so I’m bringing back another information post that was nuked – enjoy!
Something that a lot of people might not know about – fish bones. Well, to be more precise, fish ear bones. Different fish have different ear bones and they come in all types of shapes and sizes. They’re called otoliths, hard structures made of calcium carbonate that help a fish with balance and hearing. Unlike human ears that stick out, these are located in the head of the fish, pretty much directly behind the brain. How? It’s in a sac filled with hair cells, and moves along with the fish. If/When the bone hits one of the hairs, the fish’s brains gets a signal that the fish needs to figure out a better balance.
Here’s the awesome thing about fish ear bones. They record the fish’s life! Just like the rings of a tree trunk can tell a reader what types of weather patterns a tree has gone through, these serrated “ear stones” grow every year and leave behind a visible ring. The layers alternate light and dark, and that’s because of seasonal changes. In spring and summer, it’s easier for a fish to feed and grow, which leaves behind an opaque ring. When food’s not so plentiful however, growth is slow and the band darkens.
Okay, so it says if food was plentiful or not. Anything else? Why yes, there’s more! As an otolith grows it takes in metals and uses it in its structure. This means you’ll see naturally occurring metals, such as magnesium, barium, an strontium. And it also means polluting metals, like zinc, copper, nickel, cadmium, and vanadium may also appear. So now there’s a chemical history along with the fish’s personal history. (By the way, “it hurts, it hurts” disease in Toyama Prefecture was due to cadmium poisoning.)
Features of otoliths can be used (if read correctly), to identify: species, size, age, growth rate, seasons, chemical exposure, and at this rate, probably some other stuff as well about the fish (adding to the list, it can help with information about the water’s temperature and salinity levels too)!
They have another name along the beaches of the Great Lakes, specifically Lake Erie. “Lucky stones” area washed up frequently in those areas, and in other freshwater areas since these usually are the ear bones of freshwater drum (aka the sheephead fish). They’ve been found as far away as Utah and California, made into jewelry and worn. They look as though there is a “L” or “J” naturally carved into it.