Skip the store, buy right from fishermen. All coastal areas in CA have harbors and coves/piers where there is commercial fishing activity going on. Ask around where the commercial dock or hoist is; seasonal availability of the type of fish changes, but there will always be someone (the fishermen or the commercial buyer at the dock) around selling what is in season. Looks for guys in brown XTUFF boots, hoodys and orange bib-pants- probably know who might be selling fish.
Small scale fishermen use more ocean friendly gear- this includes all boats out of spots like Point Arena and Santa Cruz. Species coming out of small boats from northern and central CA include everything from salmon, halibut, lingcod, sablefish/black cod, rockfish to urchins, market squid and spotted rock prawns. Not only are you getting more sustainable and fresher fish this way, but prices are cheaper right at the source too. Hard to trust where and when fish come from in the stores: eat low on the food chain and follow sources like Sea Food Watch: http://www.seafoodwatch.org/ or the Marine Stewardship Council: https://www.msc.org/where-to-buy/product-finder