As oil prices and related exchange traded funds slipped, more energy traders are losing faith in black gold.

Over the past three months, the United States Brent Oil Fund (NYSEArca: BNO) declined 15.3% while the United States Oil Fund (NYSEArca: USO), which tracks West Texas Intermediate oil futures, fell 9.8%.

Meanwhile, the ProShares UltraShort Bloomberg Crude Oil (NYSEArca: SCO), which tries to reflect the two times inverse, or -200%, daily performance of WTI crude oil, has increased 20.0% over the past three months. The United States Short Oil (NYSEArca: DNO), which tracks the opposite moves of light, sweet crude oil, gained 9.5%. The VelocityShares 3x Inverse Crude (NYSEArca: DWTI), which tracks the daily -300% performance of oil prices, jumped 28.1%.

Brent crude futures were trading around $97.1 per barrel Monday and WTI futures were hovering around $94.2 per barrel.

Speculators have cut bets on a rising Brent crude oil price by 34% for the week ended Sept. 23, the largest weekly reduction in net longs in three years, reports Cassie Werber for the Wall Street Journal.

Meanwhile, speculators have also placed thousands of short positions, or bets that crude oil prices will continue to fall.

Hedge-funds and other large speculators also diminished their net-long positions on WTI by 4.8% in the week ended Sept. 23, Bloomberg reports.