The longer than normal cold temps kept most bodies of water colder than normal ... that slowed egg production past the normal time range for spawning ... then when it did get "warm", it did so quickly and got hotter than normal ... that shortened the time frame for a normal full-on spawn. The quick change from colder than normal water temps, to warmer than normal water temps, caught many fish not quite ready to spawn when conditions did become favorable (but trying to anyway, or just holding their eggs & absorbing them).

The fish's #1 priority is survival, not procreation. They will absorb the nutrients from eggs/milt as "food", rather than dispense them under conditions that don't promise a good percentage of surviving offspring. They instinctively know that if they don't survive, they can't very well procreate.