SEA URCHINS: The general rule when you are harvesting, is that you look for the ones in the kelp zone. Kelp is the primary source of food and it normally goes from about 20 ft to about 60-80 ft depending on the bottom. The ones that live shallower may switch to different algae for food and it may give the roe a darker color, which may be OK to eat but not as good when you are going to serve as in a restaurant. The other problem, around Palos Verdes is that the shallow SU may have worms… The deeper SU do not seem to have them…
The other general rule is that when you find them you crack a few to check for fatness, texture, and color of the roe and go from there. PV tend to have excellent SU but the abundance is not as good due to being close to the city and the resulting harvesting pressure.
The SU spawn, get skinny from that and then they go into a period of just eating and getting fat to begin the cycle again. When the are ready to spawn they may be fat and with a good color but they may get “milky” quick.
The processors crack them open, take the roe out and put them in water with salinity similar to ocean water and a food stabilizer to make the pieces firmer. Then they take them out and place them in a draining tray. They use paper towel to help in the drying of the uni, then they place them in a refrigerator and keep them there overnight. Next day they finish cleaning the pieces and pack them in the wooden tray that I am sure you have seen. Each tray, around 350 grams, has uni from 6 sea urchins on average.
Enjoy the delicacy…California has the best Urchins in the world #omnomnom