The movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to seek other fragments.
The dorsal fins are small and at the base of the tail. The largest mantas can reach 1,350 kg (2,980 lb). In both species the width is approximately 2.2 times the length of the body; M. birostris reaches at least 7 m (23 ft) in width while M. alfredi reaches about 5.5 m (18 ft).
Dive tourism involving manta rays is a growing industry, and can potentially give the giant manta ray more economic value than the short-term profits from fishing. However, the industry needs to be appropriately managed to prevent harm to the giant manta ray or its habitat and to ensure that it remains sustainable.