Here in Maine at least we had a huge boom in urchin harvesting that drove them to the edge of extinction (maybe a slight exaggeration but depletion has been dramatic). It was prior to my time as a diver but my recollections of news stories and discussions puts this in a period
through the 1990s. The harvest continues with a limited season.
Anyhow it was essentially a gold rush with the harvested urchin roe being in high demand in Japan and many people bet the farm diving for the urchins. My OW instructor actually authored state safety standards for this industry. The urchin depletion is attributed to some of the kelp proliferation we see at certain dive sites.
During this period dive shops were filling tanks as 24/7 operations. Harvesters would pay people to stand in line with their tanks to ensure that they got filled for the next day. A number of divers lost their lives in the industry. Most were under trained and under equipped diving long wet and hard when they should have been in drysuits and adhering to better practices. During this period there was lots of activity and many (of the few) dive shops in this area have compressor installations way in excess of current need and are in facilities outfitted during the boom allowing them to operate today with low overhead compared to a start-up operation. Some shop owners have attributed their current existence to this chain of events.
Here are a few links I found:
Despised Sea Urchin Enriches Maine Coast - New York Times
sea urchins
Maine Department of Marine Resources Sea Urchin Info
Pete