The European sea-urchin, Echinus esculentus L., occurs from Finnmark in the north to the Canaries in the south. Around Britain, it is found from the Isle of Portland, English Channel, throughout most of the fully saline waters of the western and northern coasts, and in the North Sea as far south as Flamborough Head. Though it occurs between tide-marks in a few places, it is generally common from about 5 m depth below c.d. to about 100 m, though it is recorded from about 200 m depth (A. M. Clark, personal communication). It is a principal browser on the reefs on which it occurs, and feeds preferentially on kelp sporelings and other algae when it occurs in the photic zone, and on encrusting invertebrates and protochordates below the depth at which algae occur (De Ridder & Lawrence, 1982). E. esculentus is said to migrate inshore prior to spawning, and then retreat to deeper water in late spring (Elmhirst, 1922; Stott, 1931; personal observation), but a rigorous study of these apparent movements has yet to be undertaken. Echinoids fare better on a diet principally of algae than on one of animal material (Lawrence, 1975), so it might be assumed that the winter inshore migration could bring an urchin into a nutritionally richer area for the final developmental phase of gametogenesis.