Spot Prawns range all along the Pacific coast, but mostly in the north Pacific.
"But one shrimp has it all: the spot prawn caught off the coast of British Columbia. The species is big, luscious, and caught in a completely sustainable manner. Its only drawback is that Canadians have recently awakened to these virtues, and devour most of the catch before it can be exported...Instead of dragging nets, spot-prawn fishermen use round, washtub-sized traps that operate on the same principle as lobster pots—prawns are lured in by containers of fishmeal and are unable to get out."
I remembered these live shrimp being offered for sale at New Sang Chong Market in Oakland Chinatown, so I went this morning and took some pictures: