Lump by name, but not by nature: 1000km migration of lumpfish (Cyclopterus lumpus)

You can tell a lot about the life history and ecology of a fish by looking at its morphology (Blake, 2004). These clues can be more obvious in some species of fish, with some features so exaggerated that they are almost a caricature, characteristic of a certain niche. Be that the extreme asymmetry of flatfish, perfectly adapted to benthic living (Livingston, 1987), or the streamline, drag optimized, morphology of sailfish, which affords them the title of the fastest sea animal (Sagong et al., 2013). However, while assumptions based on gross morphology can be useful, like any assumption, they can be misleading, with nature seemingly always able to provide an exception to the rule.

In this issue, Kennedy et al. (2025) challenge our assumptions on one of the North Atlantic's most unusual inhabitants, the lumpfish. While ‘most unusual’ is a hotly contested category, lumpfish have many features which make them excellent contenders. Features such as biofluorescence (Juhasz-Dora et al., 2022), a ventral adhesive disk (which is the source of their other common name, ‘lumpsucker’) (Brown, 1986), scaleless skin, an ability to change skin colour through their lifecycle (Davenport and Thorsteinsson, 1989), parasite eating behaviours (making them a popular sea lice prevention method in Atlantic salmon aquaculture (Ytteborg et al., 2025)) and a variety of behavioural personalities (Whittaker et al., 2021).

Perhaps the lumpfish's most unusual feature is its overall morphology, consisting of a rounded, knobbly, body, broad head and small pectoral fins. You would therefore be forgiven for thinking that this species was not capable of making long distance migrations. While this may be the case for larval and juvenile lumpfish (Moring and Moring, 1991), by tagging an incredible 2,750 individuals around Iceland and in the Norwegian Sea, Kennedy et al. (2024) demonstrate that these fish are capable of frequent long distance migration between pelagic summer feeding areas and costal spawning sites. A total of 17 tagged fish were recaptured, with two fish tagged in the east of Iceland ending up on the coast of Denmark, a staggering 1,612 km away.

This study by Kennedy et al. (2024) has shown that you cannot always judge a book by its cover, with lumpfish covering herculean distances. However, perhaps more importantly, the patterns of recapture support the Norwegian Sea being a common feeding area for several distinct populations of lumpfish, which is important information for the management of the species.