With energy and food costs rising and the economic outlook remaining murky, auto shopping activity fell sequentially for the first time in six months during April, according to Dataium, which said it hopes this decline is just a blip on the radar.

The company’s Auto Shopper Intensity index had tapered somewhat in February before becoming stronger again in March. Then, it slid last month.

The ASI index calculates overall car shopping activity throughout dealership websites and other auto portals and considers close to a dozen online shopping behaviors in its analysis.

During April, it was found that lead volume and visitors, in particular, were down. Given that spring is typically robust when it comes to demand, Dataium found this drop-off to be troublesome.

“As we have stated for a number of months now, consumer resistance has been building, and we are concerned about the ongoing weakness in the economy with rising energy and food prices possible impact on future car sales,” explained Dataium chief executive officer Eric Brown.

“We are hopeful this month’s decline in consumer intensity is only an anomaly and continued improvement in employment and declines in fuel costs will help stabilize the market going forward,” he added.

Breaking it down, the index showed the SUVs were down, just as they were in March. This month, though, sedans also were declining.

Hybrids once again climbed in terms of their index reading. The Toyota Prius, for instance, was up 17 percent.

However, the Prius was an exception to the rule for Japanese brands, as their ASI index dipped 14 percent.

“It is likely the Japanese OEMs were impacted by reductions in incentives and ongoing media coverage of supply constraints related to the tsunami and nuclear disasters,” Dataium shared.

Meanwhile, the Big 3 was off 5 percent.