In the last trading session, U.S. stocks were in the red on global growth issues. The ongoing turmoil in Chinese manufacturing sector, the end to stock purchases by government-backed funds and its impact on global markets were behind this weakness. Most importantly, oil price resumed its decline on China-led growth fears. Among the top ETFs, investors saw SPY lose about 3%, DIA shed about 2.9% and QQQ move lower by about 3.1% on the day.

Two more specialized ETFs are worth noting in particular though as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs ones to watch out for in the days ahead to see if this trend of extra interest continues:

(VOO - ETF report): Volume 3.93 times average

This S&P 500 ETF was in focus yesterday as roughly 8.3 million shares moved hands compared to an average of roughly 2.11 million shares. We also saw some stock price movement as shares of VOO lost over 3% yesterday.

The wave of China’s factory sector slowdown once again weighed on global risky assets. U.S. stocks like what we find in this ETF’s portfolio were also not spared. The fund has a Zacks ETF Rank #3 (Hold). However, for the month, VOO is down over 8.7%.

(SHY - ETF report): Volume 3.56 times average

This short-term U.S. Treasury bond ETF was under the microscope yesterday as nearly 7.3 million shares moved hands. This compares to an average trading day of 2.04 million shares and came as SHY gained about 0.04% in the session.

The movement was due to a decline in yields on the U.S. 3-year notes. The fund has a Zacks ETF Rank #3. SHY is down about 0.1% in the past one-month period.