The grey rockcod (''Lepidonotothen squamifrons''), also known as the grey notothen, stripe-eyes notothen or stripe-eyed rockcod, 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 ...
belonging to 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 ...
Nototheniidae
: ''In some scientific literature, the term "cod icefish" is used to identify members of this family. This should not be confused with the term "icefish," which refers to the "white-blooded" fishes of the family Channichthyidae. See Icefish (disam ...
, the notothens or cod icefishes. It is native to the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...
. The grey rockcod feeds mainly on macrozooplankton and is of minor importance to
commercial fisheries
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...
. It is the only species in the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Lepidonotothen''.
Taxonomy
The grey rockcod was first formally
described in 1880 as ''Notothenia squamifrons'' by the German-born British
ichthyologist
Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...
Albert Günther
Albert Karl Ludwig Gotthilf Günther FRS, also Albert Charles Lewis Gotthilf Günther (3 October 1830 – 1 February 1914), was a German-born British zoologist, ichthyologist, and herpetologist. Günther is ranked the second-most productive re ...
with the
type locality given as
Kerguelen Island
The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a group of islands in the sub-Antarctic constituting one of the two exposed parts of the Kerguelen Plateau, a large ...
. The
type was collected during the
Challenger Expedition
The ''Challenger'' expedition of 1872–1876 was a scientific program that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, .
The expedition, initiated by Wil ...
.
In 1976 the Russian ichthyologist
Arkady Vladimirovich Balushkin
Arkady (russian: Арка́дий, Arkadiy) is a Slavic masculine given name, ultimately derived from the Greek name Αρκάδιος, meaning “from Arcadia”. The Latin equivalent is Arcadius. Notable people with the name include:
People:
*Ark ...
placed it in the genus ''Lepidonotothen'',
this genus is currently regarded as
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
with this species as its sole member.
However, other authorities regard ''Lepidonotothen kempi'' as a valid species.
[ Some authorities place this taxon in the ]subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
Nototheniinae, but the 5th edition of ''Fishes of the World
''Fishes of the World'' by the American ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the ...
'' does not include subfamilies in the Nototheniidae. The name of the genus is a compound of ''lepido'' meaning “scaled”, an allusion to the scales on the top of the head and jaws of this species, and ''notothen'', indicating that it is a notothen. The specific name is a combination of ''squamis'' which means "scale" and ''frons'' meaning "forehead", a reference to the head being covered with small scales almost as far as the nostrils.
Description
The grey rockcod has an oblong body that is compressed towards the tail. It has dorsally positioned eyes that may bulge above the dorsal profile of the head, the eyes are separated by a narrow area that has a width less than the diameter of the eye. The pores in the sensory canal on the head are small. The mouth is small and does not extend to the middle of the eye and there are no large canine-like teeth. The head is almost completely scaled. There are two lateral line
The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
s, an upper and a middle line, both consisting of tubed scales. Its pectoral fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
s are smaller than the pelvic fin
Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods.
Structure and function Structure
In actinopterygians, the pelvic fin consists of two en ...
s. There are 15–17 branched rays in the rounded or truncate caudal fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
.[ The first ]dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
has 4–5 spines, the second dorsal fin has 36–37 soft rays while the anal fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
contains 29–33 soft rays. This species attains a maximum total length
Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.
Overall length
* Standard length (SL) is the length of a fish ...
of , although is more typical.[ The colour of the body is greyish above marked with 9 non-uniform, wide, dark bars that join on the underside. There is a dark stripe along the front edge of the snout extending to the lower margin of the preoperculum with a second dark stripe from the lower orbit to the angle of the preopeculum. There are two dark stripes on the upper part of the orbit. The posterior part of the first dorsal fin is blackish.][
]
Distribution and habitat
The grey rockcod is found in the Southern Ocean a far north as the Falkland Islands
The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouzet ...
and the Burdwood Bank
The Burdwood Bank, called Namuncurá in Argentina and other countries, is an undersea bank with a prominence of approximately 200 metres (110 fathoms), part of the Scotia Arc projecting some from Cape Horn in the South Atlantic Ocean and located ...
,[ ]South Georgia Island
South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east ...
and Bouvet Island
Bouvet Island ( ; or ''Bouvetøyen'') is an island claimed by Norway, and declared an uninhabited protected nature reserve. It is a subantarctic volcanic island, situated in the South Atlantic Ocean at the southern end of the Mid-Atlantic Ri ...
. This species has also been recorded from sub-Antarctic islands and the far south of the Indian and Pacific Oceans. It is a benthopelagic
The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...
fish which is found at depths of but it is most frequent at depths of .[
]
Biology
The grey rockcod is the dominant fish species in the waters off the Kerguelen Islands, which is where the greatest plankton productivity in the Southern Ocean takes place, and this population has one of the fastest rates of growth. These fish reach sexual maturity at lengths of at ages of 8 or 9 years old, faster than any other population which has been studied. The fish in this population also attain the larger known sizes than fish from the Crozet Islands
The Crozet Islands (french: Îles Crozet; or, officially, ''Archipel Crozet'') are a sub-Antarctic archipelago of small islands in the southern Indian Ocean. They form one of the five administrative districts of the French Southern and Antarcti ...
or Lena Seamounts, although South Georgia is where the largest fish have been recorded and where the rate of growth is faster than at Kerguelen.[
]Spawning
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...
occurs at the end of October in the Kerguelen and Crozet islands while in South Georgia it happens in February. Embryonic development has been estimated to takes around 2 to 3 months. In South Georgia, postlarvae which were around in standard length
Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.
Overall length
* Standard length (SL) is the length of a fish m ...
were caught in December. Females at Kerguelen could lay between 48,650 and 196,150 eggs in a season at total lengths between while at South Georgia they can lay 69,000–185,000 at total lengths between . The eggs have a diameter of .[
This species feeds mainly on larger ]zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
, mostly crustaceans
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
, cnidarians
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that th ...
and salps
A salp (plural salps, also known colloquially as “sea grape”) or salpa (plural salpae or salpas) is a barrel-shaped, planktic tunicate. It moves by contracting, thereby pumping water through its gelatinous body, one of the most efficient ...
, as well as fishes found in the water column.[
]
Fisheries
The grey rockcod is exploited by commercial fisheries. In the Kerguelen Islands only the marbled rockcod (''Notothenia rossii'') and the mackerel icefish (''Champsocephalus gunnari'') are a more important catch than this species. However, it is of much less importance to fisheries around South Georgia.[
]
References
{{Taxonbar, from=Q2661927, from2=Q2711288
Nototheniidae
Fish described in 1880
Taxa named by Albert Günther
Fish of the Indian Ocean
Fish of the Pacific Ocean
Fish of the Southern Ocean