By Nell Mackenzie

LONDON, Sept 10 (Reuters) - Trend-following hedge funds took a hit from their bets on the New Zealand dollar and Japanese stocks and bonds in August, when global markets were rattled by extreme volatility, according to Societe Generale data seen by Reuters on Tuesday.

These funds finished August with long positions in Japanese government debt, U.S. equities and the Australian and New Zealand dollars, SocGen data showed.

Some of the asset classes now favoured by the trend hedge funds that use algorithms to catch and ride price movements have proven loss-making this year, according to the data.

However, it was not clear whether they held bullish or bearish positions when they incurred the losses.

August's worst bets for hedge funds were in 10-year Japanese government bonds JP10YT=RR, the Nikkei 225 .N225, the New Zealand dollar NZD=D3 as well as German .GDAXI and Italian stock markets .FTMIB, the SocGen note said.

The Mexican peso MXN=, the British pound GBP=D3, the euro EUR=EBS, blended gasoline RBc1 and U.S. 2-year Treasuries US2YT=RR have all been losing trades this year so far, but in August they proved profitable.

The sudden reversal of crowded equity and foreign exchange trades last month was sparked by the unwinding of massive carry trades - in which investors had borrowed low-yielding currencies like the Japanese yen to buy higher-yielding assets - that in turn, generated a vicious feedback loop of equity price drops, volatility and hedge fund selling.

The market ruction was short lived and world stocks returned to record highs later in that month.

This proved tough for some trend followers, which saw double-digit performance declines during August, including Eclipse Capital Management, Drury Capital and SEB Asset Management, which all posted negative performances of over 10%, the note showed.

Drury Capital Management and SEB Asset Management are still up 3.45% and 0.57% for the year to end-August, respectively, according to the SocGen data.

Hedge funds that put on shorter-term trades recorded the best August results. These included Revolution Capital Management, Altiq and Crabel Capital Management, showed the bank data. These firms finished August with between a 3.8% and 4.5% positive performance, according to SocGen.

Altiq declined to comment. The other funds did not immediately respond.

(Reporting by Nell Mackenzie; Editing by Amanda Cooper and Angus MacSwan)

((Nell.Mackenzie@thomsonreuters.com; https://twitter.com/nellmooney;))