Necropsy Notes: Swim Bladder

This post is mostly for those from MuskieFIRST who read or participated in the "fizzing a musky" thread, but this is also meant as an educational tool for all muskie nuts.

Physoclistous: swim bladder has NO direct connection to the outside world.
Physostomous: swim bladder DOES have a direct connection to the outside world.

Muskies are physostomous (as Tfootstalker pointed out) and, as such, have an OPEN swim bladder system (as opposed to closed). In this type of system it is possible to obtain gases from above the surface, and may be one reason (in my opinion) why muskies porpoise.

So, where is the swim bladder in a muskie? It is located ABOVE most major organs (e.g., liver, stomach) and just below the kidneys and backbone. The swim bladder has a very thick membrane that was even difficult to cut with a scalpel.

Picture 1: The swim bladder is the white strip running horizontally and located just below my left thumb. You can see how high in the body it is located. Also, those are the ovaries I am holding back.

Picture 2: Close up of the swim bladder.

For those that thought they were expelling gases from the swim bladder by puncturing a small hole in the belly of the fish or near the pectoral fin, this is wrong. Perhaps there was some excess gas built up inside the intraperitoneal cavity and this method happened to work, but poking around AT ALL is a bad idea. Because these fish are physostomous, LIKE HUMANS, they can be burped. As Tfootstalker noted, gently rub their bellies from the rear (genital opening) toward their gills. This will cause any excess gas to be pushed through the pneumatic duct - which connects the swim bladder to the esophagus and is in turn connected to the outside world - and out the mouth.

Again though, please DO NOT attempt to fizz a muskie.