Twee River Redfin
Encyclopedia
The Twee River Redfin or simply Twee Redfin is a ray-finned fish species
in the family
Cyprinidae. It is placed in the "wastebin genus" Barbus
– the typical barbels and relatives – by default. But actually it is far less closely related to the typical barbels than to the South Africa
n redfins in Pseudobarbus
, and may well belong in the latter genus. Like Pseudobarbus but unlike most other Africa
n "barbs", it is tetraploid. Its closest living relative is probably the Clanwilliam Redfin
(B. calidus).
It is a smallish fish, just about 40 to 45 mm (1.6 to 1.8 in) long at sexual maturity and twice as long when fully grown. In the breeding season, males and females have the namesake red fins, but males (which are on average a bit larger) also have nuptial tubercles as typical for cyprinid
s.
, where it occurs in the Twee River to just before its confluence
with the Leeu River
, and some tributaries of the former – namely the Heks, upper Middeldeur and upper Suurvlei Rivers. Some have been introduced to dam
s of farm
s, but this was too recently to determine whether they thrive or fail in this habitat
.
Adults inhabit the deeper pools in rivers, sheltered by boulders or riparian trees. Young fish gather in schools near the water surface, associating with overhanging riparian growth, in particular Palmiet (Prionium serratum, a Thurniaceae
). The food is mainly benthic invertebrate
s; adults are also known to take other edible matter that drift
s by, such as terrestrial
insect
s that have fallen on the water surface. The breeding season extends from late spring to early summer (October to December). Egg
s – up to 400 per female and breeding season – develop iteroparously, and spawn
ing occurs after a batch of eggs has become fully developed; it is thus repeated several times during a breeding season until the entire batch of eggs has been laid. Sexual maturity
is reached at two years of age, and the species can get up to 6 years old.
by the IUCN, as its population has plummeted since 1987 to a point where it is precariously close to extinction. Only an estimated 4,100 adults remain in the world, and gene flow
between subpopulations has been cut off. The main threat is introduced carnivorous fishes. The Cape Kurper
(Sandelia capensis) is native to South Africa
but does not accur naturally in the Twee River Redfin's range; it has been introduced to the Suurvlei River, however. The kurper competes with the redfin for food and probably also eats young B. erubescens. It is the probable cause for the redfin's disappearance from the lower Suurvlei River. Competition with the Clanwilliam Yellowfish
(Labeobarbus capensis) – another South African native that was introduced to the redfin's range – has reduced B. erubescens stocks in the Twee River. Ironically, both introductions were well-meaning but misguided attempts to deal with problems caused by animals introduced from foreign countries, that failed to take into account the extremely high level of local endemism in Western Cape Province – and in the case of the Clanwilliam Yellowfish were even supported by the Cape Department of Nature Conservation. The exotic fishes that are harmful to the Twee River Redfin are the Bluegill
(Lepomis macrochirus) and the Rainbow Trout
(Oncorhynchus mykiss), illegally released in its range in the 1990, probably by angler
s. However, as these rivers have strong spring floods and high summer temperatures, neither Bluegills nor the trouts fare as well there as they do elsewhere. Additional threats include habitat destruction
by humans due to water pollution
and overuse, and clearing of riparian for orchard
s. This is especially harmful, as it deprives the young fish (which are especially under pressure by the introduced species) of their shelter, and allows surface runoff
carrying pesticide
s and fertilizer
s to pollute the rivers.
It is also listed as Endangered by the Nature Conservation Ordinance of Western Cape Province. It is illegal to kill Twee River Redfins and for the time being, it may only be caught for supervised transfer trials to other habitat
. Landowners are being educated about the uniqueness of the rivers' ecosystem
and the threat posed by advancing cultivation
right to the riverbank. As mentioned above, some translocations of this species to presumably secure areas have been started, and captive breeding
studies are being undertaken at the University of Johannesburg
. A conservation
plan is under development by CapeNature
and the South African Institute of Aquatic Biodiversity.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Cyprinidae. It is placed in the "wastebin genus" Barbus
Barbus
Barbus is a ray-finned fish genus in the family Cyprinidae. The type species of Barbus is the Common Barbel, first described as Cyprinus barbus and now named Barbus barbus...
– the typical barbels and relatives – by default. But actually it is far less closely related to the typical barbels than to the South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
n redfins in Pseudobarbus
Pseudobarbus
Pseudobarbus is a ray-finned fish genus in the family Cyprinidae. The type species is Burchell's Redfin . The scientific name is derived from the Ancient Greek pseudes and the Latin word barbus . This genus contains some of the South African redfins...
, and may well belong in the latter genus. Like Pseudobarbus but unlike most other Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n "barbs", it is tetraploid. Its closest living relative is probably the Clanwilliam Redfin
Clanwilliam Redfin
The Clanwilliam Redfin is a ray-finned fish species in the family Cyprinidae. It is placed in the "wastebin genus" Barbus – the typical barbels and relatives – by default. But actually it is far less closely related to the typical barbels than to the South African redfins in...
(B. calidus).
It is a smallish fish, just about 40 to 45 mm (1.6 to 1.8 in) long at sexual maturity and twice as long when fully grown. In the breeding season, males and females have the namesake red fins, but males (which are on average a bit larger) also have nuptial tubercles as typical for cyprinid
Cyprinid
The family Cyprinidae, from the Ancient Greek kyprînos , consists of the carps, the true minnows, and their relatives . Commonly called the carp family or the minnow family, its members are also known as cyprinids...
s.
Distribution and ecology
It is endemic to the Western Cape Province of South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, where it occurs in the Twee River to just before its confluence
Confluence
Confluence, in geography, describes the meeting of two or more bodies of water.Confluence may also refer to:* Confluence , a property of term rewriting systems...
with the Leeu River
Leeu River
Leeu River, , The Leeu Taaiboschspruit Catchment is situated in the Greater Sasolburg area in the Free State, South Africa.- Also see :* List of rivers of South Africa* List of reservoirs and dams in South Africa...
, and some tributaries of the former – namely the Heks, upper Middeldeur and upper Suurvlei Rivers. Some have been introduced to dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
s of farm
Farm
A farm is an area of land, or, for aquaculture, lake, river or sea, including various structures, devoted primarily to the practice of producing and managing food , fibres and, increasingly, fuel. It is the basic production facility in food production. Farms may be owned and operated by a single...
s, but this was too recently to determine whether they thrive or fail in this habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
.
Adults inhabit the deeper pools in rivers, sheltered by boulders or riparian trees. Young fish gather in schools near the water surface, associating with overhanging riparian growth, in particular Palmiet (Prionium serratum, a Thurniaceae
Thurniaceae
Thurniaceae is the botanical name for a family of flowering plants. Such a family has been recognized by most taxonomists.The APG II system, of 2003, also recognizes such a family, and assigns it to the order Poales in the clade commelinids, in the monocots...
). The food is mainly benthic invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s; adults are also known to take other edible matter that drift
Drift
- Film and literature :* Drift , a 2002 Doctor Who novel* Drift , a series of Japanese films written and directed by Futoshi Jinno* Drift, 2007 experimental short film by Max Hattler* Drift , a fictional character...
s by, such as terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s that have fallen on the water surface. The breeding season extends from late spring to early summer (October to December). Egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s – up to 400 per female and breeding season – develop iteroparously, and spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
ing occurs after a batch of eggs has become fully developed; it is thus repeated several times during a breeding season until the entire batch of eggs has been laid. Sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is reached at two years of age, and the species can get up to 6 years old.
Status and conservation
This species is considered Critically EndangeredCritically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
by the IUCN, as its population has plummeted since 1987 to a point where it is precariously close to extinction. Only an estimated 4,100 adults remain in the world, and gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
between subpopulations has been cut off. The main threat is introduced carnivorous fishes. The Cape Kurper
Cape kurper
The Cape kurper is a species of fish in the Anabantidae family. It is endemic to South Africa.-References:* Skelton, P. 1996. . Downloaded on 5 August 2007....
(Sandelia capensis) is native to South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
but does not accur naturally in the Twee River Redfin's range; it has been introduced to the Suurvlei River, however. The kurper competes with the redfin for food and probably also eats young B. erubescens. It is the probable cause for the redfin's disappearance from the lower Suurvlei River. Competition with the Clanwilliam Yellowfish
Clanwilliam Yellowfish
The Clanwilliam Yellowfish is a ray-finned fish species in the family Cyprinidae. It has long been placed in Barbus, the "wastebin genus" for barbs, by default; however, the species is increasingly being restored to related yellowfish genus Labeobarbus which seems a much more appropriate placement...
(Labeobarbus capensis) – another South African native that was introduced to the redfin's range – has reduced B. erubescens stocks in the Twee River. Ironically, both introductions were well-meaning but misguided attempts to deal with problems caused by animals introduced from foreign countries, that failed to take into account the extremely high level of local endemism in Western Cape Province – and in the case of the Clanwilliam Yellowfish were even supported by the Cape Department of Nature Conservation. The exotic fishes that are harmful to the Twee River Redfin are the Bluegill
Bluegill
The Bluegill is a species of freshwater fish sometimes referred to as bream, brim, or copper nose. It is a member of the sunfish family Centrarchidae of the order Perciformes.-Range and distribution:...
(Lepomis macrochirus) and the Rainbow Trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
(Oncorhynchus mykiss), illegally released in its range in the 1990, probably by angler
Angling
Angling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
s. However, as these rivers have strong spring floods and high summer temperatures, neither Bluegills nor the trouts fare as well there as they do elsewhere. Additional threats include habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
by humans due to water pollution
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
and overuse, and clearing of riparian for orchard
Orchard
An orchard is an intentional planting of trees or shrubs that is maintained for food production. Orchards comprise fruit or nut-producing trees which are grown for commercial production. Orchards are also sometimes a feature of large gardens, where they serve an aesthetic as well as a productive...
s. This is especially harmful, as it deprives the young fish (which are especially under pressure by the introduced species) of their shelter, and allows surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
carrying pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s and fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s to pollute the rivers.
It is also listed as Endangered by the Nature Conservation Ordinance of Western Cape Province. It is illegal to kill Twee River Redfins and for the time being, it may only be caught for supervised transfer trials to other habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
. Landowners are being educated about the uniqueness of the rivers' ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
and the threat posed by advancing cultivation
Tillage
Tillage is the agricultural preparation of the soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shovelling, picking, mattock work, hoeing, and raking...
right to the riverbank. As mentioned above, some translocations of this species to presumably secure areas have been started, and captive breeding
Captive breeding
Captive breedingis the process of breeding animals in human controlled environments with restricted settings, such as wildlife reserves, zoos and other conservation facilities; sometimes the process is construed to include release of individual organisms to the wild, when there is sufficient...
studies are being undertaken at the University of Johannesburg
University of Johannesburg
The University of Johannesburg came into existence on 1 January 2005 as the result of a merger between the Technikon Witwatersrand and the Rand Afrikaans University . Prior to the merger, the Daveyton and Soweto campuses of the former Vista University had been incorporated into RAU...
. A conservation
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
plan is under development by CapeNature
CapeNature
CapeNature is a governmental organisation responsible for maintaining wilderness areas and public nature reserves in Western Cape Province, South Africa.-West Coast:*Cederberg Wilderness Area...
and the South African Institute of Aquatic Biodiversity.