Lepidonotothen
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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 fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...
belonging to the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
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 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...
. 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 p ...
. It is the only species in the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''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, 35,800 species of fish had been described as of March 2 ...
Albert Günther Albert Karl Ludwig Gotthilf Günther , also Albert Charles Lewis Gotthilf Günther (3October 18301February 1914), was a German-born British zoologist, ichthyologist, and herpetologist. Günther is ranked the second-most productive reptile tax ...
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 region. They are among the most isolated places on Earth, with the closest t ...
. The
type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
was collected during the
Challenger Expedition The ''Challenger'' expedition of 1872–1876 was a scientific programme 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 W ...
. In 1976 the Russian ichthyologist
Arkady Vladimirovich Balushkin Arkady () is a Slavic masculine given name, ultimately derived from the Greek language, Greek name Αρκάδιος, meaning “from Arcadia (region), Arcadia”. Endeared versions of the name are ''Arkasha''. The Latin equivalent is Arcadius (disa ...
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 "unisp ...
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 botanical subfamily names with "-oideae", and zo ...
Nototheniinae, but the 5th edition of ''
Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...
'' 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 Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
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 epithelia ...
s, an upper and a middle line, both consisting of tubed scales. Its
pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...
s are smaller than the
pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...
s. There are 15–17 branched rays in the rounded or truncate
caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...
. The first
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
has 4–5 spines, the second dorsal fin has 36–37 soft rays while the
anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...
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, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...
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 (; ), commonly referred to as The Falklands, 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 from Cape Dub ...
and the Burdwood Bank,
South Georgia Island South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...
and
Bouvet Island Bouvet Island ( ; ) is an uninhabited subantarctic volcanic island and dependency of Norway. It is a protected nature reserve, and situated in the South Atlantic Ocean at the southern end of the Mid-Atlantic Ridge, it is the world's most extre ...
. 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 (; 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 Antarctic Lands. History ...
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 Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
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 fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...
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 heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
, mostly
crustaceans Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...
,
cnidarians Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
and salps, 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