Brian Hunter and the Amaranth Collapse

Brian Hunter was a natural-gas trader at Amaranth Advisors whose relentless accumulation of long positions in natural-gas futures destroyed a $9 billion hedge fund in less than a month in September 2006. Hunter’s conviction that prices would spike was not inherently irrational—it was the magnitude of his bet, the leverage behind it, and his refusal to adapt when the market moved against him that turned a credible thesis into catastrophic loss.

The trader: Hunter’s rise

Brian Hunter joined Amaranth Advisors in 2003, coming from Deutsche Bank where he had built a reputation as an aggressive natural-gas trader. Amaranth, founded by Nick Maounis, had grown rapidly through the 2000s, managing billions in hedge fund assets and targeting multiple strategies. The natural-gas desk was one of its strongest franchises, generating steady profits from volatility trading and arbitrage.

Hunter was smart, brash, and confident. He had studied engineering and approached trading as problem-solving: he would identify edges in natural-gas spreads—differences in prices across contracts and locations—and exploit them through systematic trading. His early years at Amaranth were hugely profitable. The fund’s investors and management celebrated his talent, and Hunter’s stature inside the firm grew steadily.

But success bred overconfidence. By 2005 and early 2006, Hunter had begun to migrate from the disciplined arbitrage strategy that had made him famous toward outright directional bets. He developed a thesis: winter was coming, storage levels were low, and natural-gas prices would spike. It was not an unreasonable view—natural gas is highly seasonal, and tight supply conditions do indeed presage higher prices.

The position: Building the bet

What began as a bearish view evolved into an obsessive bet. Hunter started accumulating long positions in natural-gas futures contracts, particularly in the spread between the nearby contract (the month being traded now) and longer-dated contracts. His initial size was large but reasonable for a billion-dollar energy trading operation.

But as the months of 2006 wore on, Hunter did not take profits. Instead, he doubled down. He added to his long position repeatedly, convinced that prices would move higher. He funded much of this accumulation with leverage—borrowing from counterparties and using derivatives to amplify his exposure. By August 2006, Hunter controlled a natural-gas position so large that his trades moved the market materially when he entered or exited. He had become, in effect, the natural-gas market.

Management at Amaranth appears to have been aware of the size of Hunter’s position but did not constrain it aggressively. There were several reasons: his historical profitability was exceptional, natural-gas trading was notoriously difficult to model, and Maounis and his risk team may have believed that Hunter’s volatility was a feature, not a bug. The fund’s leverage and risk management systems were not designed to stop a single trader from building a position that represented the majority of the fund’s capital.

The market turns: Conviction meets reality

In early September 2006, natural-gas prices did not go up. Instead, they went sideways, then down. Hunter’s bullish thesis was failing. Rather than acknowledge the error and cut losses, Hunter held. This is where the story transitions from a large bet to a catastrophe. Every day the market moved against him, his losses mounted. Margin calls began. Amaranth had to post more collateral to keep the positions open.

The brutal mathematics became clear: if natural gas fell another 10–15%, Amaranth would face a liquidity crisis. Counterparties and creditors would demand immediate payments. The fund would not have enough cash to meet redemptions and maintain its positions. The core of risk management is position sizing: if you size correctly, you can survive being wrong. Hunter and Amaranth had violated that principle.

By mid-September, the fund’s leadership realised they had a crisis. Hunter’s position was so large and so underwater that liquidating it would crash the natural-gas market and crystallise losses that might exceed USD 6 billion. Amaranth began desperate negotiations with major investment banks to find a buyer for the entire book of trades.

The collapse: Weeks to zero

Over a gruelling few days and weeks, Amaranth tried to sell its natural-gas position to a consortium of buyers. In the end, Citadel agreed to take the position for a discounted price, likely salvaging some value but cementing Amaranth’s loss. The hedge fund that had managed USD 9.2 billion and generated stellar returns for years was now in free fall.

Investors were told that withdrawals would be suspended and that the fund would unwind over time. The final tally: Amaranth lost approximately USD 6.6 billion in a single month—one of the largest hedge fund blow-ups on record. The firm that once aspired to be a multi-strategy powerhouse effectively ceased to exist as a going concern.

Why it happened: The architecture of failure

The Amaranth collapse was not the result of Hunter acting alone; it was a failure of institutional risk management at every level. Several factors compounded:

1. Concentration: Hunter’s position represented the majority of the fund’s capital, violating basic diversification principles.

2. Leverage: The position was funded heavily with borrowed money, which amplified both gains in the early years and losses when the thesis failed.

3. Conviction without flexibility: Neither Hunter nor senior management was willing to accept that the thesis might be wrong and cut losses when they were still manageable.

4. Institutional overconfidence: Success in 2003–2005 bred complacency about the risks in 2006.

5. Opacity: The natural-gas market was less transparent and more difficult to model than equity markets, which made it easier for a single trader to accumulate an outsized position without immediate detection.

Aftermath and lessons

Hunter’s career in institutional finance was effectively over. Some reports suggested he eventually pursued smaller-scale trading operations, but he never regained prominence. Amaranth was wound down. Nick Maounis’ reputation took a hit, though he had been largely absent during the natural-gas concentration.

The Amaranth collapse became a textbook case in risk management failures and triggered introspection across the industry. It demonstrated that even intelligent traders with a defensible thesis can destroy billions if position sizing and leverage are not controlled ruthlessly. The lesson: edge and conviction matter, but they are worthless if you bet more than you can afford to lose.

For energy traders, the Amaranth collapse illustrated another lesson: when one trader becomes the market, reversals are swift and unforgiving. John Arnold, who was shorting natural gas as Hunter accumulated his long position, profited enormously from the unwinding. The contrast between Hunter and Arnold—both brilliant traders, one destroyed and the other made extraordinarily wealthy—hinges on discipline and risk management.

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