Am not an expert in turtles biology. At first sight I would expect trade-offs between predation and foraging. The places where marine turtles forage are probably very good places in terms or food resources, which implies a large gradient of the food chain and so predators. These places are probably not suitable for the juveniles. 

Yes but what other aspect affect for this?

hi,

Data accumulated from several decades of mark–recapture and telemetry studies demonstrate that adult sea turtle migrations are resource-driven, with migrants traveling hundreds to thousands of kilometers between established feeding and breeding areas at regular or seasonal intervals.

We believe that mainly it is food resources and nesting grounds/beaches characteristics.

For more details on sea turtles migratory patterns, you may read the book "The biology of sea turtles Vol. 2, (Lutz p. et al, 2002)".

Lutz, P. L., Musick, J. A., & Wyneken, J. (Eds.). (2002). The biology of sea turtles (Vol. 2). CRC press.

cheers, Kostas