Here are some generalizations. I write this realizing that there always are exceptions to generalizations.
I generally tell my pondowners that smallmouths mature about an inch smaller than largemouths. It's a reasonable, general rule of thumb.
For most fishes, it is size that determines if they are mature, not age. If you stock 2-inch fingerling LMB into a new, fertile pond in TX or MO, they almost always spawn at age 1 (the next spring). However, in SD, they almost never spawn at age 1 -- very rarely, anyway. The key is the different growing season lengths and the eventual size at spring age 1. LMB males typically can spawn at perhaps 11 inches, while females are more likely to spawn by 12 inches. Now, old, slow-growing fish can spawn an inch or so earlier, but these are reasonable numbers.
For the smallies, I typically expect most 10 inch males to be mature, while most females are mature by 11 inches.
