''Macrourus berglax'', the roughhead grenadier or onion-eye grenadier, is a species of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Macrouridae Macrouridae is a family of deep sea fish, a diverse and ecologically important group, which are part of the order of cod-like fish, the Gadiformes. The species in the Macrouridae are characterised by their large heads which normally have a singl ...

. It is a deep-water fish found in the Atlantic Ocean.

Description

The roughhead grenadier can reach a length of one metre. The head occupies about one quarter of the total length of the fish, it has a slender body and long tapering tail. There are some bony spiny scutes or scales on the upper side of the head but the lower side is scaleless. The snout is pointed and the small mouth is set far back on the lower side of the head with a short barbel underneath. There are 3 to 5 rows of sharp teeth in the upper jaw and 1 or 2 rows in the lower jaw. The eye is large and bulbous, giving the fish its alternative name of onion-eye grenadier. There are two dorsal fins, the front one having 11 to 13 finrays and the hind one running along the back to the tip of the tail. The anal fin is similarly long and narrow and there is no tailfin. The body is covered in large ridged, spiny scales. The general body colour is grey, darker underneath, with dark fins and dark edges to some of the scales.

Distribution

The roughhead grenadier is found in the North

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

at depths between and water temperatures below . Its range includes the waters around

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

and

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

, and extends in the west from the

Bear Seamount The Bear Seamount is a guyot or flat-topped underwater volcano in the Atlantic Ocean. It is the oldest of the New England Seamounts, which was active more than 100 million years ago. It was formed when the North American Plate moved over the New ...

, Norfolk Canyon and

Georges Bank Georges Bank (formerly known as St. Georges Bank) is a large elevated area of the sea floor between Cape Cod, Massachusetts (United States), and Cape Sable Island, Nova Scotia (Canada). It separates the Gulf of Maine from the Atlantic Ocean. Th ...

north to

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

and the

Davis Strait Davis Strait is a northern arm of the Atlantic Ocean that lies north of the Labrador Sea. It lies between mid-western Greenland and Baffin Island in Nunavut, Canada. To the north is Baffin Bay. The strait was named for the English explorer Jo ...

and in the east from

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

north to the

Faeroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway betwee ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

Spitzbergen Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group range ...

and the

Barents Sea The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territo ...

Biology

The roughhead grenadier feeds on crustaceans and other small invertebrates it finds on the seabed. The diet includes small fish,

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...

polychaete worms Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are m ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

molluscs,

isopods Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomo ...

s, other echinoderms and

comb jellies Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), an ...

. The roughhead grenadier is a slow growing fish. The females mature at an age of about 14 years and a length of while males reach maturity at a length of . The potential fecundity of the female is 17,000 to 56,000

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

. The eggs are laid in batches and spawning takes place at any time of year, with a peak in late winter and early spring.

Fishery

The roughhead grenadier is landed as a

by-catch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

when fishing for

Greenland halibut The Greenland halibut or Greenland turbot (''Reinhardtius hippoglossoides'') belongs to the family Pleuronectidae (the right-eye flounders), and is the only species of the genus ''Reinhardtius''. It is a predatory fish that mostly ranges at dept ...

(''Reinhardtius hippoglossoides'') and Atlantic halibut (''Hippoglossus hippoglossus''). In a study off the east coast of Greenland, more males were taken by trawling and more females by long line. This seemed to be due to the females being in the depth range while the males predominated at shallower depths.

References

{{Taxonbar, from=Q2466797 Macrouridae Fish described in 1801