In addition to eating salmon, i take fish oil caps because of family history of alzheimer's. should i give them up because of link to prostate cancer?

Yes and no: The evidence that suggests there is a protective effect from fish oil against alzheimer's is weak and tentative. I wouldn't take it for that indication. While we're at it, the link showing reduced heart disease is weak too. The strong link is eating fish. Your salmon is good.

Fish oil: The fish oil link to prostatic ca is not proven as far as I am aware.