Ethan Roberts knows about mackerel discipline first hand. Mr. Roberts, who was released in 2007 after serving eight years on a methamphetamine charge at prisons including the La Tuna Federal Correctional Institution in Texas, says he got busted for various piscine transactions. "I paid gambling debts" with mackerel, he says. "One time I bought cigarettes for a friend who was in the hole."
Frankly, other than linking to our old friend, I'm not sure what else I can add.
Mackerel Economics in Prison Leads to Appreciation for Oily Fillets [Wall Street Journal]