What's the Chinese for sustainably fished?

It was pouring when I got out of my appointment in Chinatown on Saturday, so I decided to skip my usual farmer's market outing. There are many food stores between the subway and my appointment, so I stopped in to buy my favorite dried plums. I also stopped at the fish store. I could've bought tuna or salmon fillets, but I would've felt ridiculous asking if they were sustainably fished. There were some small silver fish and Bottom Feeders generally recommends eating fish low on the food chain, but I had no idea what kind they were or how to cook them. One of the guys there asked, in reasonable English, "Can I help you?" I asked, "What kind of fish are those small ones?" "Small fish." *head slap forehead*

I think I'll stick to my usual fishmonger, thanks.