NEW YORK (CNNMoney.com) -- New York energy hedge fund MotherRock L.P. is closing down after suffering major losses in the natural gas market, according to a report published Friday.

MotherRock was one of the biggest hedge funds in New York trading natural gas futures, The Wall Street Journal reported.

The fund was formed early last year by former New York Mercantile Exchange President J. Robert Collins and gained 20 percent in 2005, the newspaper said.

MotherRock managed approximately $430 million in assets at its height in May, but movements in the natural gas market and investor redemptions led to big losses in June and July, the Journal said, citing a source close to the matter.

The natural gas market has seen major volatility in the past two weeks as soaring temperatures across the country have pushed up demand and prices.

Tough times continue for hedge funds