isn't afraid of the man.  In fact the fish rises slowly toward the man and watches.  It feels as if Hughes is suggesting that the fish is letting the fisherman know "you're in my world now."  The biggest commentary on human nature through all of this is that humans are not as special as they think.  Mankind is simply a piece of the natural world.  Man has his own niche; he is a part of the natural world, not above it or ruling over it, but subject to all of its beauty and brutality. 

In the first stanza, Hughes suggests the violence possessed by pikes:

"Killers from the egg: the malevolent aged grin.
They dance on the surface among the flies."

The word "killers" needs no further explanation. The pike is born with an instinctive desire to kill and "malevolent" suggests that the fish has an inherent evil; it is naturally vicious.

Stanza four further develops the idea of how malignant the pike can be:

"The jaws’ hooked clamp and fangs"

It is clear that the pike's jaws are specially designed: it first "hooks" and then "clamps" down, finally finishing off its prey with its fangs. This tells us that the pike can effectively capture and destroy whatever prey comes within its reach. There is no, or very little chance of, escape. The image of prey trapped in those fearsome jaws is both violent and horrific.

In stanza six, Hughes emphasizes how ruthless pikes are:

"And indeed they spare nobody."

The pikes do not discriminate. They attack and eat whatever they can, cannibalizing even their own kind, as is made clear in stanzas five and seven:

"Three we kept behind glass,
... Suddenly there were two. Finally one" (stanza 5)
"One jammed past its gills down the other’s gullet" (stanza 7)

It is clear throughout the poem that pikes are vicious and terrifying creatures and that they are naturally inclined to be so. These fish are a metaphor for the instinctual violence that exists in nature which is, no matter how frightening, essential for survival. 

Hughes reveals his admiration for the pike in the poem "Pike" through vivid imagery and figurative language.  He contrasts their powerful form and lethal hunting skill with their graceful ability to move through the water.  The poem's beginning line showcases his utter respect for the fish, "three inches long, perfect" (1).  The stripes of the fish are characterized by his word choice "tigering" which likens the fish's subtle camouflage to that of a tiger.  Both the tiger and the pike are powerful predators in their own environment, and Hughes' diction reflects the pike's command of the water.

As the poem continues, Hughes writes of the fish as if they were ancient monsters; the pike in the pond were "Pike too immense to stir, so immense and old" (35).  He speaks of them reverently, tinged with a healthy amount of fear for their powerful jaws and teeth.  Hughes sees the pike as a worthy adversary, one deserving of his respect.

The overwhelming way in which nature, through the creatue of the pike that this excellent poem focuses on, is presented as a dangerous, scary and terrifying place. The pike itself is depicted as a relentless predator, that will continue to follow its murderous instincts even in death, as the following image shows:

Two, six pounds each, over two feet long 
High and dry and dead in the willow-herb- 

One jammed past its gills down the other's gullet: 
The outside eye stared: as a vice locks- 
The same iron in this eye 
Though its film shrank in death.

This memory that the poet has of coming across two dead pikes, who had fought each other to the last, coupled with his experiment of putting three pikes in a tank and seeing how, one by one, they disappeared until only one remained, "With a sag belly and the grin it was born with," serve to create a menacing, frightening impression of nature. The last few stanzas show how the pike is not only a violent predator in its own world as the poet himself feels almost like an intruder as he fishes for pike:

Owls hushing the floating woods 
Frail on my ear against the dream 
Darkness beneath night's darkness had freed, 
That rose slowly toward me, watching.

He is scared to fish for the pike yet he is unable to stop himself, but all the time he imagines this ancient and ruthless predator watching him and his pathetic attempts to fish with his violent eye. The lingering image of the pike coldly and cooly watching the poet in a calculated way serves to consolidate the presentation of nature as being a violent force of ruthless and calculated predatory instinct.