• Scientific name: Coryphaenoides rupestris
  
• Also know as: Ratfish, Rat-tail, Whip-tail, Rock Grenadier, Black Grenadier
• Size: Up to 3 to 4ft in length and 8lbs
• UK minimum size: N/a
• IGFA world record: 7lb 6oz
• IUCN Status
  • Global: CR (Critically Endangered)
  • Europe: EN (Endangered)
• Distribution: Deep-sea species with the only British/Irish populations in the Rockall Trough and Faroe-Shetland Channel.
• Feeds on: Predatory fish which feeds mostly on small fish and squid, as well as mid-water crustaceans.
• Description: Large, rounded head and the body tapers down to a pointed tail. The eyes are large, the mouth is relatively small, and there is a small barbule present on the chin. The scales are large and hard giving this species a tough skin. The first dorsal fin is very high and triangular, with the second dorsal fin very small, long and barely visible. The anal fin is elongated and runs the length of the underside of the body. Flanks and back are usually grey to light brown in colour with fins sometimes being black.

The roundnose grenadier is a deep-sea species of fish which was, like the orange roughy, mostly ignored by commercial fisheries until the 1970s. Since then it has been exploited heavily to the extent that the species is at risk of extinction. The International Union for the Conservation of Nature to class it as a Critically Endangered species on a global basis and Endangered in European waters.

Distribution

The roundnose grenadier is a very deep water fish which can be found in depths of several hundred metres but is more commonly found at around 1500 – 2000 metres. In British and Irish waters this restricts the roundnose grenadiers distribution to the very deep waters of the Rockall Trough to the west of Ireland and the Faroe-Shetland Channel to the north of Scotland. It is found elsewhere in the world around deep-water seamounts (underwater mountains) and continental slopes, with populations of roundnose grenadier found around the New England Hotspot in the middle of the Atlantic, in the deeper waters around the Grand Banks and Georges Bank in North America and in the deep waters around Iceland, Greenland and Scandinavia.

Feeding, Behaviour and Reproduction

Although roundnose grenadier is a small fish, seldom exceeding three feet in length, they are hunters and feed primarily on small squid and fish, as well as deep-water shrimps, prawns and amphipods. Larger, mature roundnose grenadier are thought to make a daily vertical migration up to mid-water during daylight hours to hunt pelagic fish which are found there. Sometimes shoals of this species can form to hunt for preyfish in mid-water. Roundnose grenadiers can themselves become prey for larger species which live at these depths. Like most deep-water species the roundnose grenadier is a slow-growing, late-maturing fish which has a long life span. This species is thought to live for up to seventy years and needs to be at least ten years old before it can reproduce.

Commercial Fishing

The roundnose grenadier is a perfect example of a fish which was previously ignored by the commercial fishing industry but has become increasingly valuable as stocks of traditional whitefish such as cod, haddock and plaice have declined. The reasons for ignoring roundnose grenadier are clear to see – its deep-water habitat makes it difficult and expensive to catch and the hard scales of this species make it difficult and costly to process. Furthermore due to its shape of a large head and long tail only around a quarter of the overall weight of a roundnose grenadier is edible flesh. Despite these drawbacks by the 1970s, it became apparent that with the large subsidies some commercial fishing operations receive money could be made by catching this species and deep-water factory trawlers from several different countries began heavily targeting roundnose grenadier. While the first half of the 1960s saw no roundnose grenadier caught at all, figures from the Food and Agriculture Organisation of the United Nations state that 84,000 tons were caught in 1974 alone.

Being a late-maturing and long-lived fish the roundnose grenadier could not reproduce fast enough to replace the amount of fish that were being taken, and stocks soon crashed. Writing in his famous book on overfishing The End of the Line in 2004 Charles Clover states that “stocks of the roundnosed grenadier west of the British Isles are now so low that they are below the precautionary level set by the ICES [International Council for the Exploration of the Sea] – the level at which fishing should theoretically stop.” The Joint Nature Conservation Committee, the statutory adviser to the UK government on national and international nature conservation, stated in 2010 that “If action not taken [this species is] likely to become extinct in the next 10 years.” The International Union for the Conservation of Nature classes this species as Critically Endangered globally and Europe’s stocks are classed as Endangered.

ICES have officially recommended that the commercial fisheries for roundnose grenadier are not allowed to expand and catches should be limited to 1000 tons per year. This was followed by the Deep Sea Conservation Coalition (an international body made up of around sixty organisations including Greenpeace, Oceana and the Pew Charitable Trust) calling for all fishing for roundnose grenadier to stop by setting the total allowable catch (TAC) of this species at zero. If these restrictions are put in place there is a chance that the numbers of roundnose grenadier will stabilise and possibly increase in the coming years, although due to the slow-growing nature of this species a significant increase in numbers will take a very long time indeed.

Rod and Line Caught Records

As a deep-sea species there is unsurprisingly no British shore caught or boat caught record for this species. However, the IGFA (International Game Fish Association) does list an all-tackle world record for this species. The record is held by Tommy Ruste who caught a 7lb 6oz roundnose grenadier in July 2018 when fishing at Trongfjorden, Norway.