When smoking was banned from federal prisons in 2004, cigarettes lost their value as prison currency. Justin Scheck’s “Mackerel Economics” in the Wall Street Journal tells what happened next:

Prisoners need a proxy for the dollar because they’re not allowed to possess cash. Money they get from prison jobs (which pay a maximum of 40 cents an hour, according to the Federal Bureau of Prisons) or family members goes into commissary accounts that let them buy things such as food and toiletries. After the smokes disappeared, inmates turned to other items on the commissary menu to use as currency.

Books of stamps were one easy alternative. “It was like half a book for a piece of fruit,” says Tony Serra, a well-known San Francisco criminal-defense attorney who last year finished nine months in Lompoc on tax charges. Elsewhere in the West, prisoners use PowerBars or cans of tuna, says Ed Bales, a consultant who advises people who are headed to prison. But in much of the federal prison system, he says, mackerel has become the currency of choice.

Some prisoners end up with massive mackerel stocks. At least one lawyer was paid in mackerel.