The fish-hook is the Aquarian man captured by the preceding Christ-Pisces in relation to the future sunrise over the equinox into the House of Aries, the new Emperor. Offcourse it is much more complex than that, but Crowley's words concern the new paradigm of Man. Aquarus, Pisces and Aries play pivotal roles.
The paradox is in the retrograde motion of 0 degree Aries equinox sunrise from the first degrees of Pisces into the last degrees of sign Aquarius.
Hidden in this paradox is the mind bending problem of the path forwards to enlightenment, the birth of the new emperor man in the first house of Aries; and meanwhile regressing backwards from the last sign into the eleventh: the waterbearer.
Which, by the way, uncovers the answer to the sphinx's riddle. The backside of this monument points almost to the lion and its face will be illuminated by the sunrise in the last degrees of Aquariuas, which then are by our understanding the first degrees in this sign. The Emperor, house of Aries, the firstborn, occupied nowadays by the fish hook which is the border between old Fish and new Water Bearer.