related high volume keywords = most important?

Is the related keyword with highest volume that google spits out when using the keyword tool also the most relevant keyword in google's eyes?

Is this the algo behind how google determines if a page is relevant about a keyword?

example:

[fly fishing]49.500 <- main keyword that I want to rank as high as possible

keyword tool suggestions with highest volume:


[fishing tackle]40.500
[flies]33.100
[fishing rods]14.800

some of the suggestions with low search volume:

[discount flies fishing]< 10
[saltwater fly fishing combos]< 10
[bass fly fishing poppers]< 10
[fly fishing wader bags]12
[fly fishing rod reel combos]12


I now build a page targeting to rank high for "fly fishing" not including(theoretically-ok!) the related keywords with most volume but I include some related keyword with very low search volume.
Another page about "fly fishing" I use the related keywords with high volume but leave the ones with low volume.

Which page will google give more relevancy regarding search term "fly fishing"?
I guess the one with most volume related keywords cause I think google will think(lol) that it has more data on the high volume searches.

Otherwise they would need some fly fishing expert that tells them "fly fishing rod reel combos" should be on every page related to fly fishing thus making every page that dont have that keyword not relevant.

dont want answers which tell me whats best for my visitor