Seasonal and age-related migrations in the unexpectedly long-lived benthic fish the lesser weever, Echiichthys vipera (Cuvier, 1829)

Abstract

A study of an inshore southern North Sea population of lesser weever, Echiichthys vipera, on the Suffolk coast, England, found this small, abundant, benthic fish to reach an age of 15 years and suffer an adult mortality rate of only 0.23 y−1. The maximum length observed of 195 mm Standard length (SL) (225 mm total length, TL) was the greatest yet reported and many individuals >140 mm SL (163 mm TL) were caught between 2009 and 2012. Previous studies have reported a maximum of 160 mm TL and a von Bertalanffy asymptotic TL of 150.3 mm. Age structure analysis showed that recruitment into the local inshore Sizewell population continued until 5 or more years of age. A 6 year age of recruitment corresponds to the age when they have been reported to have disappeared from offshore locations and previously assumed to have died from old age. Regular seasonal changes in local abundance were observed with peak captures during May, presumably caused by seasonal immigration, followed by a summer minimum and a second, more variable, maximum in early autumn before the winter minimum. The winter minimum in captures may be due to either inactivity or offshore migration. Lesser weever has evolved a long-lived, slow growing, life history strategy unusual for small benthic fish in the southern North Sea. By spending long periods hidden in sand, using venom for defence and remaining inactive for an extended period each winter, lesser weever has adopted a strategy which favours high survival and increased longevity.