They eat small fish and have a migratory pattern similar to that of the mackerel, arriving a short time before the latter to spawn. Their association with mackerel has led to some older common names such as "mackerel guide" and "mackerel guardian".[1] They move into shallow waters in April and May and spawn in areas with eelgrass in May and June. In the autumn, they return to the open sea, including the Atlantic west of Ireland and Great Britain.