All I know is that the southern charter fleet is fishing north of the bridge over the past month or so. A friend of mine took his company out on a one of their boats and the captain claimed the Omega fleet took a big chunk of the bait this year down there. No bait, no food for the rockfish. I don't know where all the spot have gone the last few years.
Spot will run in a cycle - abundance of small ones - then bigger ones as they grow up. Most only live 3-4 years and they are eaten by many other fish.
No doubt the use of them as live bait has taken a toll. The smaller 3-5 inchers can be trapped - IMHO - not a good idea. Often far too many are taken and wasted when held overnight in live pens. The smaller ones are fragile compared to bigger ones.
Spot also can be killed by very cold winters - few years ago hundreds of thousands of them died in the bay. At first reports - thought it was Menhaden but photos clearly showed it to be dead Spot. That summer - it was tough finding Spot.
There has been increasing pressure on Spot in our bay - many are sold live in Delaware and New Jersey in fall. Fishermen in these states pay $2.00 to $3.00 per Spot on retail end. Wholesale end is about $1.00 each.
Good news - Spot do seem to repopulate quickly. Likely 2016 will see a lot of the tiny 1-3 inches and 2017 will have plenty of the 4-7 inchers so good for live lining.