The greatest threat against adult whelks
are cod, wolffish, rays and starfish, while sea-urchins and starfish predate
on their eggs. The whelk by smelling the water can detect a predator closing
in, and protects itself by violently moving its foot and turning over its
shell and thus rolling away from its assailant.
The whelks enemies
The starfish - enemy and friend
The whelk can appear to have a strange relationship
with certain starfish; most studied is its relation with the starfish Leptasterias
polaris. This starfish is found the North American coast and resembles
the Spiny starfish
(Marthasterias glacialis), a common species in Swedish
waters. Although the starfish is a predator, whelks can sometimes surround
it. There are three possible explanation for this strange behaviour; (1)
the whelk steals food from the starfish with its long siphon, (2) they are
waiting for remains, (3) they eat food such as worms and mussels that have
became more accessable after the starfish has stirred up the bottom sediment.
The reasons why whelks congregate around Leptasterias polaris which
eats large mussels are several; (1) large prey emits several chemical signals
that make it easier for whelks to find food, (2) starfish have difficulty
covering large prey, which makes it easier for the whelk to reach the prey,
and (3) the starfish can be satisfied earlier when devouring larger prey
and therefore leave more remains for the whelk.