A composite image of Sam Bankman-Fried (left) and mackerel fish (right).

Sam Bankman-Fried image by ED JONES / Contributor/Getty Images. Mackerel image by Anadolu / Contributor/Getty Images

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It didn't take long for the former crypto-billionaire Sam Bankman-Fried to learn the economic system of New York's Metropolitan Detention Center.

The disgraced founder of the crypto exchange FTX has been keeping busy by swapping food items in exchange for services as he awaits sentencing on seven felony counts that include wire fraud and conspiracy to commit money laundering.

The new polished haircut he has been seen with in New York courtrooms appears to be thanks to an inmate. In a Thursday report, a source told The Wall Street Journal that SBF paid for a haircut with packaged mackerel, a type of pelagic fish that is a choice of currency among inmates.

It's no surprise that the former trader would quickly catch on to the commodity of choice in his new environment. He has been a professional trader for much of his career. In 2013, he got his first intern gig at Jane Street Capital, swapping exchange-traded funds before cofounding his crypto-trading firm Alameda Research in 2017. A year later, he figured out how to arbitrage bitcoin between the US and Japanese markets.

The fish, popularly referred to as "macks" among inmates, had been the choice of currency in federal prisons since 2004 after cigarettes were banned, sources told the Journal in 2008.

The formerly incarcerated attorney Larry Levine accepted it as a form of payment from fellow prisoners he represented while serving his own sentence at the Lompoc correctional institution in California, the Journal previously reported. He then used them to pay for personal-upkeep services such as beard trims and shoeshines from inmates, the outlet added.

Global Source Marketing, a supplier of the fish, told the Journal in 2008 the trend had become so popular that it felt the increased demand.

There's economic logic behind the trend. Products that have steady value, such as certain food items and stamps, are used as a steady means of exchange to substitute for currency, which inmates cannot access. Food items such as mackerel and tuna are stable commodities with a value that can be pegged to the dollar.

Bankman-Fried, who's set to be sentenced on March 28, 2024, faces up to 110 years in prison for the fraud charges brought against him, but they're only part of the charges he's facing. He's also set to stand trial for separate counts related to political bribery.

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Laila was one of the most widely read reporters covering financial markets as an Investing Correspondent in New York.Her articles are a product of original reporting on stocks, bonds, commodities, derivatives, forex, and crypto. She profiled successful fund and quant managers and occasionally wrote about macroeconomics, banks, and financial crime. Features: How a free meal cost an investor his retirement savingsWhen deposits go missingWhen Wall Street's financing turns 'toxic'Predicting the election outcome & its shock impact on the 10-yearTop traders: A simple trade from a quant manager's toolbookA veteran bond operator's alpha-generating strategy4 indicators of a multimillion-dollar retail trader9 indicators for a short seller's 90% win ratioA commodities trade with Fibonacci retracementsA trader's bitcoin bet in a triple tax benefit accountHigh-net-worth investors: The wealthiest 0.01% are firing their active managersThe ultrawealthy's dash for private credit8 of the savviest loopholes to skip capital gains taxTV appearances include:  CBS, FOX Business, ABC, NewsNation, FOX 5, NBC lx, and Business Insider's video explainers.Notable interviews include: Ray Dalio, David Booth, Rick Rieder, David Rubenstein, and Sam Bankman-Fried.