* Sales fall 0.1 pct vs estimate of 0.6 pct decline
* Volumes rise 0.4 pct
* Oil and aerospace falls are main drivers
OTTAWA, June 13 (Reuters) - Lower prices unexpectedly caused the value of Canadian factory sales to decline in April, by 0.1 percent from March, but the volume of sales rose by 0.4 percent, according to Statistics Canada data released on Friday.
The median forecast in a Reuters survey of analysts was for a 0.4 percent increase in the current-dollar value of sales. The constant-dollar or volume figure, which strips out price changes, is relevant for calculating increases in real gross domestic product.
Despite the decline in the dollar value of sales, gains were posted by 14 of 21 industries, representing about 60 percent of manufacturing.
Partial refinery shutdowns that were more extensive than usual helped cause a 5.0 percent decline in the value of sales in petroleum and coal products. The lumpy aerospace industry also dropped 6.2 percent after three solid months of gains. Weakness in these sectors hit Quebec particularly hard in April.
Economic bright spots included a 12.1 percent rise in the paper industry, the largest since the current data series began in 1992; and a 3.3 percent rise in the auto industry, with the motor vehicle parts industry at its highest level since October 2007.