- Scientific name: Coryphaenoides rupestris
- Also know as: Rat-tail, Whip-tail, Rock Grenadier, Black Grenadier
- Size: Up to 3ft and 5lbs
- UK minimum size: N/a
- UK shore caught record: N/a
- IUCN status: CR (Critically 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. Body tapers down to pointed end. Eyes are large, the mouth is relatively small, and there is a small barbule present on the chin. Scales are large, hard and closely connected to the body with very small spines present, 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 and is now in serious trouble, leading to the International Union for the Conservation of Nature to class it as a Critically Endangered species.
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 are 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 grenadiers are thought to make a daily vertical migration up to mid-water during daylight hours to hunt pleagic fish which are found there. Sometimes large 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 and long living fish. This species is thought to have a lifespan of up to seventy years, and needs to be at least ten years old before it can reproduce.
The roundnose grenadier is a perfect example of a fish which was previously ignored by commercial fishermen but has become extremely valuable as stocks of traditional whitefish such as cod, haddock and plaice have dropped.The reasons for ignoring roundnose grenadier are clear to see – its deep-water habitat makes it difficult and expensive to catch, and although the flesh is highly prized for its flavour and succulence 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 massive subsidies commercial fishermen get money could be made by catching this species. Deep-water factory trawlers from many different countries began targeting this species heavily. 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 the keep up with the numbers 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.” Furthermore, 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
The ICES (International Council for the Exploration of the Seas) has officially recommended that the commercial fisheries for roundnose grenadier are not allowed to expand and catches should be limited to 1000 tons per year. 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. However, due to the slow growing nature of this species a significant increase in stocks of roundnose grenadier will take a very long time indeed.