I use a water elemental slayer scrappers compendium on my fisher (and, although I don't need it, it has additional +magery on it), and when I'm fishing, I will often summon a water elemental and an air elemental (to use all 5 slots, and give me two caster allies) if there's a chance something will show up.
I would suggest using a 105 or 110 Magery PS so that if you have jewelry or a book to put you over 100, you can utilize it (and summons fail a lot more than they should; every little bit helps).
If you run without Eval int, then the only spells you need worry about are travel spells, healing/curing, summons and Mind blast. All the damaging spells that the slayers would help on are dependent on Eval, and I don't know if they ever changed Mind Blast to get SDI from bonuses or slayer (it definitely didn't a few years ago, at least for the slayer).