The Brazilian guitarfish (''Rhinobatos horkelii'') is a species of

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

in the family Rhinobatidae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, where its natural

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

is coastal waters on the continental shelf. This fish is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

and has a long gestation period, concluding with the birth of live pups in February. At this time the fish are subject to intense fishing activity but catches have been dwindling in recent years as a result of

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

. Because so few breeding-size fish remain, the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed the fish's conservation status as being " critically endangered".

Taxonomy

The Brazilian guitarfish was first described as ''Rhinobatos horkelii'' by Müller & Henle in 1841. They named the new species in honour of the German botanist, Dr.

Johann Horkel Johann Horkel (8 September 1769 in Burg auf Fehmarn – 15 November 1846 in Berlin) was a German physician and botanist. From 1787 he studied medicine at the University of Halle, where in 1802 he was named an associate professor. From 1804 to ...

, Professor of Plant Physiology at the

University of Berlin Humboldt-Universität zu Berlin (german: Humboldt-Universität zu Berlin, abbreviated HU Berlin) is a German public research university in the central borough of Mitte in Berlin. It was established by Frederick William III on the initiative o ...

, who had sent them a specimen of the fish preserved in alcohol.

Description

This species can grow to a length of , but a more usual adult size is about . The dorsal surface is a uniform olive-grey or brown. There is a dark patch on the snout and the nostrils are long. The crown is transversely flattened or slightly convex.

Ecology

Arraia viola (Rio de Janeiro, Brazil, 20 July 1865)

The Brazilian guitarfish is a low-fecundity

fish. Mating takes place on the inner continental shelf in March and soon afterwards the adults disperse to outer areas of the shelf. The eggs are contained within a casing and remain dormant inside the female until she return to the warm, shallow waters of the inner

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

in November. The young develop inside the female, at first obtaining nourishment from their yolk sacs, and later from maternal uterine secretions; they grow from a length of about in December to about in February when they are born. The females mature at about 4 years of age and litter sizes range from 4 to 12, with larger fish having larger litters. The inner shelf provides important nursery areas for the young fish. Here both females and juveniles are particularly susceptible to being caught by pair-trawling and beach seine netting. Most of the catch is pregnant females. Later in the year, the adults disperse more widely over the inner shelf and are caught by otter-trawling.

Status

The major threat faced by ''R. horkelii'' is overfishing. The fish is caught by trawling, beach seine and gillnet and has traditionally been the main

batoid Batoidea is a superorder of cartilaginous fishes, commonly known as rays. They and their close relatives, the sharks, comprise the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 fam ...

fish caught along the coast of southern Brazil. The main ports at which it is landed are

Rio Grande The Rio Grande ( and ), known in Mexico as the Río Bravo del Norte or simply the Río Bravo, is one of the principal rivers (along with the Colorado River) in the southwestern United States and in northern Mexico. The length of the Rio G ...

and

Itajaí Itajaí () is a municipality in the state of Santa Catarina, Brazil. It is located on the northern central coast of Santa Catarina and is part of the Vale do Itajaí Mesoregion, on the right bank of the Itajaí-Açu river mouth. It lies at th ...

. In 1975, 842 tonnes were landed at Rio Grande and by 1984, that had risen to 1804 tonnes. Since then the catch has dwindled to 157 tonnes in 2002 and has continued to decline since. In southern Brazil waters, the fish seems to have declined by more than 80% since 1986. Based on this evidence, the

is concerned that the Brazilian guitarfish may become extinct within about ten years due to overfishing, and has therefore assessed its conservation status as being " critically endangered".

References

{{DEFAULTSORT:guitarfish, Brazilian Brazilian guitarfish Fish of Brazil Endemic fauna of Brazil Marine fauna of South America Southeastern South American coastal fauna Critically endangered fish Critically endangered biota of South America Fish described in 1841 Taxonomy articles created by Polbot Taxobox binomials not recognized by IUCN