This is an especially powerful poem for anyone who has ever seen a pike. "Teeth" hardly seems to describe the jagged edges in their mouths, making them very unlike most fish one expects to find in lakes, ponds, etc.
In Ted Hughes' poem entitled "Pike," the author is able to convey a great deal with his use of imagery in nature. This literary device occurs when a writer creates vivid images in the reader's mind—often by using sensory details...details that appeal to the senses.
One terrifying image is found in the line:
Killers from the egg; the malevolent grin.
The fear in this statement comes (for me) from the image of this creature being a killer from birth. The use of personification is present in giving the fish a "grin"—and a malevolent one at that. The sense of horror is intensified with this facial image because malevolent is defined as having a conscious intent to cause harm.
Another frightening line is...
Of submarine delicacy and horror.
The image of a submarine lying in wait to attack those unsuspecting creatures above also creates a sense of terror, as well as fear and awe in the mental image evoked by...
The jaws' hooked clamp and fangs...
With regard to sensory details, the use of "hooked" and "fangs" is impactful from a tactile perspective: a reaction to the biting pain experienced by a finger being caught on a fork-tipped hook. (Though "hooked" may refer to "jaw's," the image connects automatically for me with "fangs.")
The poem continues to become even more powerful and frightening as the poet describes keeping three of these creatures in a fish tank. However, it is their nature that leads to the demise of two...for they eat each other. One's skin crawls to read:
Suddenly there were two. Finally one.
With a sag belly and the grin it was born with.
And indeed they spare nobody...
One jammed past its gills down the other's gullet...
Their savagery is channeled vividly with this imagery...it is frightful that their nature is so ferocious that they cannibalize one another...even when the size of the other fish—the prey—defies digestion.
There is also the simile used that promotes awe:
The outside eye stared: as a vice locks—
The eye of the fish being devoured is unmoving, like a vice that is locked. And the final image of that eye is fearsome as well:
Though its film shrank in death.
Perhaps the last thing that I find terrifying as I imagine myself in the author's place is the image of him fishing in the pond, which is as deep as "England." He notes his fear of casting at night—in that pond with ancient pike; but that with a "splash" (onomatopoeia) comes the sense in the darkness of...
...pike too immense to stir, so immense and old...
...That rose slowly toward me watching.
This image also uses personification as well: for a fish will naturally "see," but not "watch"—this requires intelligence and intent that a mere fish would not have. The vivid sense of fear here at the poem's end reflects the purpose and intellect of one of these "Killers from eggs."
With regard to the author's creation of "atmosphere," it is hard to say if this mood or tone: for if the author is to be believed, it is both. The mood is how the writer wants the reader to feel. The tone is how the author personally feels about his subject: these often are not synonymous. However, in this poem, the author seems to experience a healthy fear or terror of pike, and he succeeds in creating that same feeling in the reader!
[Poem text courtesy of National University of Bangladesh English Literature Blog.]