I''m just back from the beach with a bag of kutai (50 individual mussels) for my 68th birthday dinner, "tom yum mussels".
Mussel gathering is not easy at Okarito. It is such a wild seacoast churned by large rollers from the southern ocean. Mixed in the turbulent surf are vast amounts of sand and gravel that comes from the glacial rivers. The net result is that mussels can gain a foothold only well out from the shoreline where they escape the worst of the grinding gravel.
Humans can only risk access to the mussel zone when calm seas coincide with the lowest of tides. Even then don't take your eyes off the sea. Tangaroa (the Maori God of the sea) tries to swallow you every seven waves or so. You work perched on boulders with white-water surf swirling all around. I wear non-slip crocs and a life-jacket to give me some chance in a worst case scenario. The plainly obvious danger protects the mussels from over exploitation.
Once on site there is still no guarantee of satisfaction. Mussels are at their tastiest just before spawning which appears governed by the season and nutrient supply. But there is no way of knowing this without cracking and eating a raw mussel. If it tastes bitter then go back home.
How you pick is also important. Select individuals that are prominent in the clumps or are slightly isolated to get the best. Mussels compete for nutrients so the sweetest and fattest are those that filter the currents first .
Get all these ducks lined up and you're rewarded with plump orange or cream coloured mussels that taste best immediately after steaming - YUMMMMMM!