> What triggers the fish into spawning behaviors-water temp, day length?

It would be nice to have some kind of formula for this but bass don't conform to hard and fast rules. In general water temperature above 60 degrees triggers spawning, and fish will spawn up into the high 70's that I've observed anyway. Fish may spawn above or below those ranges, but that's the general time when they spawn. Photoperiod (the length of the day) may certainly have an effect on when fish spawn but there's no largemouth on earth you can convince to spawn in 40 degree water even if it's a long day in March :)

> How do you determine the sex of a black bass?

Male bass, like Don pointed out, seldom get larger than 5lbs. I've caught a few males over 5lbs but it's pretty uncommon. If you see two bass on a bed, the larger one will be the female 99% of the time. You will see more than one female on a bed but never more than one male, they won't tolerate eachother. The most female bass I've ever seen on a bed was 4 at a time.

Male bass will sometimes have a hooked lower jaw, like a salmon, this seems to be a variation that happens only on certain lakes. They usually look skinnier than females, and if you catch one on a bed and starts shooting white stuff around, well... then you know. There's no perfect way to determine the sex of a bass without cutting it open, but in the spring you can usually make an educated guess.

> How does varying water levels affect spawn?

Bass are pretty determined when it comes to reproduction. Ideally the water doesn't go up or down during the spawn, but the bass make do regardless. Bass, especially the males, will often stay on the bed during dropping water to the point where their backs are almost out of the water. Bass on the delta where the tides cause the water to go up and down twice daily will spawn in areas where on a low tide they will be almost exposed completely. I think their basic goal is to make the bed where it gets a reasonable amount of sunlight, then guard it as long as they can. In lakes where the water levels vary a lot it can affect the spawn, but the thing is... bass lay so many eggs and spawn for such a long period of time that they have a knack for making millions of babies regarless of what is happening.