Just tested the Delock 91694 FireWire 800 CompactFlash Reader under Mac OS X El Capitan (10.11.1). The Delock's 91694 FireWire 800 Reader worked flawlessly, mounting two different SanDisk Extreme® CompactFlash 60MB/s UDMA 16GB cards, and a Transcend 4GB 133X card.
Under 10.4 through 10.9 iPhoto opened automatically when the reader was connected or when new CompactFlash cards were inserted. Mac OS X El Capitan is the second Mac OS version to deploy the new Photos app, which does not automatically launch. However, when we opened Photos and navigated to the import function, the CompactFlash card present in the reader was there and ready for importing with the preview feature.
We had no issues with the Delock 91694 FireWire 800 CompactFlash Reader under Mac OS X El Capitan (10.11+). Here is a screen shot of the PCM-CR-FW81ECF-03 / 91694 working under Mac OS X El Capitan (10.11.1). Our MacBook Pro has a FireWire 800 port and a Thunderbolt port.