Sea Shorts: Wonderful wolffish and their amazing adaptations

You might be thinking there is something strange about the fish in the header image - and you’ll be right. These are not real fish. They are toys. But they do represent real fish. Yes, there really are fish in the ocean that look like that! May I present from left to right, the spotted wolffish (Anarhichas minor), the northern wolffish (Anarhichas denticulatus), and the Atlantic wolffish (Anarhichas lupus)! Lets take a look at one of them in a little more detail- the Atlantic wolffish.

Atlantic wolffish have adapted to life in cold water, even ‘freeze risk ecozone’ - areas where, thanks to extensive sea ice formation, sea water temperatures can reach -1.8°C! Yup - that’s cold. Compared to the closely related spotted wolffish, Atlantic wolffish have five times more antifreeze protein in its plasma, which allows them to survive in these harsh conditions. Genetic work has uncovered how Atlantic wolffish achieve such high levels of antifreeze proteins - they have three times the amount of antifreeze protein gene copies, and several times higher antifreeze protein transcript levels in their liver!

Thanks to the Atlantic wolffish’s antifreeze capabilities, they have been suggested as candidates for aquaculture development in cold-water locations. In the quest to produce an economically viable cold-water aquaculture species, some people are looking to hybridise Atlantic wolffish with spotted wolffish, which have higher growth rates at cold temperature. As an added bonus to aquaculturalists, Atlantic wolffish boast high survival rates, relatively easy-to-rear larvae, high resistance to stress and handling, and produce high-quality meat in captivity.

Yes meat - they may not look very attractive, but for some they quite tasty. Apparently the meat is firm and mild-tasting - and lacks small intermuscular bones that normally you have to carefully pick out before eating.

A real Atlantic wolfifsh! Credit:  Citron/Wikimedia  ( CC BY-SA 3.0 )

A real Atlantic wolfifsh! Credit: Citron/Wikimedia (CC BY-SA 3.0)

Unsurprisingly given their appearance, wolffish are often sold at the retail level as skinned and boned fillets, and often given more appealing names. In the UK, Atlantic wolffish are used in ‘fish and chips’, where it is called ‘Woof’, ‘Scarborough Woof’, or ‘Scotch Halibut’.

Food isn’t the only use people have found for Atlantic wolffish. Their liver is said to produce a high-quality oil similar to cod, whilst its leathery skin which varies in colour from slate blue, to olive green, to a purplish-brown colour, has been used for a multitude of purposes. Today, you can even find a case for your mobile telephone, a wallet, or a pair of shoes in wolffish ‘leather’.

Sadly Atlantic wolffish populations are not in good shape. Swedish landings of Atlantic wolffish in the Kattegat Sea declined by approximately 70% in the last 40 years. In the USA, bycatch landings declined 95% since the early 1980s, whilst in Canada, scientific trawl surveys have indicated an overall population decrease over the same time period. Atlantic wolffish are listed as a ‘species of concern’ by the USA’s National Marine Fisheries Service. Further north in Canada, the species has also been listed as ‘special concern’ under the Species at Risk Act. Across the Atlantic, the Helsinki Convention (HELCOM) - the governing body of the "Convention on the Protection of the Marine Environment of the Baltic Sea Area", have listed the species on their Red List as ‘endangered’.

The primary cause of the wolffish’s decline appears to be fishery-related. Even where they are no longer allowed to be deliberately caught, they end up as bycatch in bottom gear like trawls. These same trawls also destroy their ‘nests’ - the spots where wolffish lay their eggs, making it even harder for populations to bounce back.

The Sea Shorts series offers tiny glimpses into all things ocean and coastal. Read more Sea Shorts and other stories here.

Header image: Three (toy) wolffish species. From left to right, the spotted wolffish (Anarhichas minor), the northern wolffish (Anarhichas denticulatus), and the Atlantic wolffish (Anarhichas lupus).