I found this:
"Fisherman's Hope" by David Feintuch
Published in 1996 by Warner Books,it weighs in at 482 pages. One error noted.
Capt. Nicholas Seafort has time and again come to the rescue of humanity in their struggle against the strange 'Fish', a species of space being that can 'Fuse' for travel between the stars and planets, a technology recently discovered by humans that has allowed them to start colonizing local star systems. Use by the humans of Fuse technology attracts the Fish, who have attacked star ships and colonies as a result. So far, none have come to Sol system.
Capt. Seafort is a bad politician, so he gets assigned to the position of Commandant of the Naval Academy to help rebuild the devestated Fleet of planet Earth. He's also wracked by guilt as the only way he's been able to do what he has done is by violating the very codes and principles he holds dear, even mutiny when necessary to save the ship and what he could of its crew.
After a short 'boot camp' on Earth, the Cadets are shipped up to the far side of the Moon for space and Officer training. On Seafort's first trip outside with his charges some skittish behavior by the nervous cadets leads to a smashed faceplate, and the first flagstone in Seafort's new soul-wracking trip down guilt lane. A path that leads to desperate measures when the Fish start showing up in Home system, and he's left weaponless in the face of a seemingly implacable foe. Or is he weaponless, and if not at what cost?