This is the most appropriate case in which to use the word "boundary." A line that sets a limit on a map (for example, to limit the extent of a country) is called "boundary." It can also be called "border" or "frontier." Although the word "edge" is often a synonym, it cannot be used in the same way in this particular case.
The commander of Naval Education and Training Command (NETC) is currently a 2-star admiral. NETC itself is located at Naval Air Station Pensacola, Florida.
Salmon's need to lay many eggs because the eggs are very fragile. These eggs are not very likely to survive and hatch. Lots of eggs need to be laid to guarantee the survival of at least some of the eggs.