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July 24, 2006

Stomach Eversion Explained

While fishing out of Quepos, Costa Rica, I noticed that about one of every five billfish we caught had their stomachs protruding into their mouths, like bottomfish brought rapidly to the surface...

While fishing out of Quepos, Costa Rica, I noticed that about one of every five billfish we caught had their stomachs protruding into their mouths, like bottomfish brought rapidly to the surface. I wasn't sure what to do, and conventional wisdom among local captains is to do nothing. They claim once the fish is released the problem will take care of itself. However, our captain did take the time to stuff an everted stomach back into a 350-pound blue marlin before we let it go. Do billfish have swim bladders? If so, what's the best thing to do for the fish in this situation?

Tom Ogle   
Beaufort, South Carolina


A: Billfish do have swim bladders, albeit small ones. In fact, the bladders are so small that they could not push the stomach through the mouth as happens with many deepwater species. Rather, it appears that billfish are physiologically susceptible to stomach eversion when under stressful conditions like being hooked and played. One theory holds that this predisposition makes it easier to get rid of squid beaks that may lodge in the stomach wall. There do not appear to be any studies about the effects of stomach eversion on survival rates of released billfish. However, I get the sense that postrelease survival in this situation is high, so stuffing the stomach back down the throat is not necessary. On the other hand, gently doing so will likely do no harm and might even be beneficial.
- Milton Love