Aloha Kathy,
Mahalo for your question. Taking shells is not illegal according to the Kahuna’s consultants, but your concern is appropriate. If you’re a collector, then you’re probably seeking specific samples, like a good auger or opihi. If you’re filling out a collection and not taking buckets from the beach, you’re not doing much damage.
Otherwise, the Kahuna recommends a catch-and-release system. Pick up a nice shell or a small bag full, admire them in your room or on the lanai, then have a nice ceremony before you leave where you return them to their home on the beach. It’s fun and reduces the strain on the shell supply.
Have a nice visit,
Big Kahuna