One pattern I've been onto for a long time "theoretically" is spring carp. My own experiences over the years combined with friend's experiences have taught me that early spring is the best time to get very aggressive carp. The will pounce on crankbaits, jigs, flies and other presentations at this time.
Why is this the case?
I did a bit of reading on carp, and articles I found in "Fishing For Buffalo" mentioned that carp have small stomachs - they need to keep feeding constantly. Carp are also omnivores. They can eat everything from nymphs to crawfish and from minnows to cottonwood seeds. Vegetable matter = dinner!
What happens is that as water temperatures start going up quickly in the early spring, the carp's metabolism goes up accordingly, yet the food chain - plant life and animal life, has not yet caught up to the carp's appetite! So the carp MUST eat, but there isn't much around! Wait until June and July and sure, you can catch carp - but they have the choice of what they want to eat. They can afford to be selective! Carp can't afford to be selective in late March and in April - they HAVE TO EAT!
As a kid I caught a 23lb carp off the Webster Pier near Rochester in late April/early May on a mr. twister jig. I also caught fish in the spring in Irondequoit Creek on jigs. My buddy Eric caught 2 or 3 in a row in early April off the Ithaca "Wall" on rapalas! Last week I had one hit a jig in Skaneateles Lake in 34/35 degree water. Today (April 3rd.) I got a monster on a flashy chartreuse streamer! These aren't coincidences. The carp are hungry as heck now. Get them while they're hot!