Male midshipman fish have a unique way of finding a female in the cloudy waters of the Pacific Ocean, they hum and hum and hum.
They can hum for a really long time — up to an hour — without stopping to take a breath. See how long you can hum. Or listen to their loud hum in a YouTube video that can be found at www.youtube.com/watch?v=BwUT778RovI.
To make their attractive noise, the fish are able to use the muscles around their swimbladder. A swimbladder is a pouch in their body that is filled with gas. The pouch lets the fish float so they don’t have to swim so hard. The muscles around the midshipman fish's swimbladder are able to squeeze, or contract, up to 100 times in a second to make that humming noise. That’s 360,000 times in an hour, which sounds like it would be exhausting.
That’s a pretty amazing task considering the plainfin midshipman fish only grows to about 15 inches long. It is a member of the toadfish family, which live on the bottom of the ocean.
Other fish have the same ability to call female partners to their nest, including the male Atlantic toadfish. It can contract and relax its swimbladder muscles up to 200 times a second, but it makes a shorter call mixed with long silences.
A couple of other cool things about the midshipman fish: It can breathe air when it is out of water and parts of its body will glow when it is seeking a mate, another way it attracts females in cloudy, dark water. This lighting ability is known as bioluminescence, which is a mouthful of a word. Fireflies are also bioluminescent, as are some jelly fish.
— Brett French, firstname.lastname@example.org