They were there, on the first piece of kelp we looked at. On the side facing down into the sea, just where the fronds join the stipe. A little cluster of five, each no bigger than a fingernail.
It had almost been too easy. But, looking back the clues had been there a few weeks before, when we had found, amongst the usual limpets and topshells, some small soft-brown domes with barely visible pale stripes radiating from one end. Apparently a type of limpet, but not looking like any of the textbook illustrations. We had wondered then if they were old and worn blue-rayed limpet shells.
Checking online and in our favourite textbook1 it appeared that blue-rayed limpets often feed on a species of kelp known as Laminaria digitata; a large brown fingered seaweed which grows on rocky shores and is usually only accessible at the lowest of low tides. I knew from sailing that these tides, ‘spring tides’ typically occur twice a month, near full and new moons, when the alignment of the earth moon and sun produces maximum gravitational pull. Looking at our local tide tables, we noted the date and time of the next such tide.