Orion's Hounds (Star Trek: Titan, Book 3)

As the USS Titan ventures beyond the outermost reaches of known space, the telepaths in her crew -- including Diplomatic Officer Deanna Troi -- are overwhelmed by an alien cry of distress which leads the crew to a scene of shocking carnage: a civilization of interstellar 'whalers' is preying upon a familiar species of sentient spaceborne giants. Appalled but reluctant to rush to judgement, Captain William Riker and his crew investigate, discovering a cosmic spawning-ground in a region of active star formation -- the perfect ecosystem for a bewildering array of diverse but similarly vast lifeforms. While attempting to negotiate an end to the exploitation and victimization of these creatures, Riker's crew inadvertently hands them the means to defeat their hunters' purpose...only to learn that things are not quite what they seem.