Both spee-sees and spee-shees are acceptable.

How do you pronounce it?

SPEE-SEES…unless I’m just talking about the female half, then it is SPEE-SHEES.

I shay ‘shpeeshees’ shometimesh, if I have shomething in my mouth while I’m shpeaking, like perhapsh a shucker.

Am I the only one saying speckies?

Very possibly yes. I use the first with a slight emphasis on the first syllable.

I pronounce it /ˈspiːsiːz/ .