Lumpfish(Cyclopterus lumpus) is a high latitude species mostabundant in Arctic and sub-Arcticwaters of the North Atlantic. Vertical behaviour of this fish is unclear as it is often caught by both pelagic and demersal trawls. To gain greater insight into its behaviour, 41 female lumpfish caught during the Icelandic Groundfish Survey (IGFS) in Marchwere tagged with data storage tags (DSTs); the IGFS finishes?1 week before the beginning of the lumpfish fishing season (20 March).Data retrievedfromreturned tagswere comparedwith informationondepth anddistributionof catches of lumpfish from the IGFS. Thirteen tags were returned with days at liberty ranging from 20 to 61 d. Maximum depth recorded was 308 m (maximum depth of the tag) but based upon interpolation of temperature recordings, one fish may have descended to ?418 m. Lumpfish dis- played a range of vertical behaviours termed demersal, surface, and pelagic. During March, most exhibited either demersal or pelagic behaviour but the time spent in surface behaviour increased from March to April. During demersal behaviour, depth was rarely constant indicating the fish were not stationary. Both DSTand catch data fromthe IGFS indicate that lumpfish exhibit diel patterns in vertical behaviour. Aslumpfish frequently exhibitdemersal behaviour, the use of the IGFS tomonitor changes in abundance is justified. As lumpfish spend a significantamount of time in both the pelagic and demersal zone, they should be considered as a semi-pelagic (or semi-demersal) fish during this life stage/time of year.