Endemic Cyprinid Research Articles

Determination of hormones inducing oocyte maturation in Chalcalburnus tarichi (Pallas, 1811)

Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17alpha,20beta,21-trihydroxyprogesterone (20beta-S), progesterone (P), 17alpha-hydroxyprogesterone (17alpha-HOP), 11-deoxycortisol (11-DOC), and 17alpha-hydroxy-20beta-dihydroprogesterone (17,20beta-P) were measured in fish caught from Lake Van and the Karasu River, and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated in vitro with different doses (50, 200, and 1,000 ng/ml) of 20beta-S, 17alpha-HOP, 11-DOC, and 17,20beta-P. 11-DOC was found to be the most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20beta-P could not be determined in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels (P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion, 11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this species.

Threatened fishes of the world: Onychostoma alticorpus (Oshima, 1920) (Cyprinidae)

The conservation status, species identification, distribution, specific habitat and ecology of a threatened, endemic cyprinid fish, Onychostoma alticorpus (Oshima 1919) is reported herein. It is merely found in five river basins of Taiwan. The protection of natural habitat would be very essential.

Comparative phylogeography of endemic cyprinids in the south‐west Iberian Peninsula: evidence for a new ichthyogeographic area

The comparative phylogeography and evolutionary history of three native cyprinid genera, Squalius (subfamily Leuciscinae), Chondrostoma (subfamily Leuciscinae) and Barbus (subgenus Luciobarbus; subfamily Cyprininae), were examined focusing mainly in the South‐Western region of the Iberian Peninsula, where recently described endemic species are present with considerably restricted distribution areas. In order to accomplish that the variation at the complete cytochrome b gene (1140 bp) was analysed for specimens from the South‐Western region, and also for representatives of the three genera from all over the Iberian Peninsula. Data indicate different evolutionary histories, with distinct time periods of colonization between the two cyprinid subfamilies in the Iberian Peninsula. Four new Iberian ichthyogeographic areas are accordingly proposed based on congruent phylogeographic and geological evidences: the South‐Western, the South‐Eastern, the Atlantic and the Mediterranean. Evidence was provided for the older isolation of the South‐Western area in the Miocene during the Endorheic Drainages phase, designating a clearly defined and distinct ichthyogeographic area. A new molecular clock calibration is proposed for the subgenus Luciobarbus.

Hydrological impacts affecting endangered fish species: a Spanish case study

AbstractThe Júcar River Basin (Spain) harbours endemic aquatic species that are declining or going extinct at an alarming rate. After evaluating several possible stressors, flow modification is identified as the factor critically threatening one endemic cyprinid fish species Chondrostoma arrigonis. Physical habitat for this species is compared for river reaches with different flow modification histories to understand local extinctions across this species' historical range. Time‐series of physical habitat, generated using PHABSIM, indicate a dramatic reduction in habitat area with flow modification. Our findings indicate that efforts to regulate and stabilize flows in the Júcar River Basin may cause the rapid extinction of the remaining populations. Copyright © 2007 John Wiley &amp; Sons, Ltd.

EFFECTS OF TEMPERATURE ON THE SURVIVAL AND GROWTH OF AGE-0 LEAST CHUB (IOTICHTHYS PHLEGETHONTIS)

Larval and juvenile stages of many fishes require nursery habitats that provide optimal conditions for growth. Loss or degradation of these habitats limits recruitment, causing population and species declines. Least chub (Iotichthys phlegethontis), an endemic cyprinid in the Bonneville Basin, is currently restricted to a few spring complexes in Utah. This species utilizes the warm shallow spring margins as spawning and rearing habitat throughout the summer. This study was conducted to determine effects of temperature on survival and growth of age-0 least chub to understand the importance of temperature in selection of spring margins as rearing habitat. Age-0 least chub were exposed to 5 tem- peratures (14°C, 17°C, 21°C, 24°C, and 27°C) for 112 days. Growth rates varied significantly with temperature except at 17°C and 27°C, and growth rates were highest at 21°C (P < 0.001). Maximum growth rate for age-0 least chub, estimated from a 2nd-order polynomial regression, would occur at 22.3°C. These thermal requirements indicate the importance of warm rearing habitats in producing strong year classes and viable populations. However, warm spring margins also enable western mosquitofish, a nonnative competitor and predator of least chub, to thrive in these spring habitats. Broad thermal limits of the least chub suggest that it could persist at cooler temperatures, which would reduce the viabil- ity of western mosquitofish populations.

Age and Growth of an Endemic Cyprinid Fish, Spinibarbus yunnanensis, from Lake Fuxian, China

ABSTRACT Age and growth of Spinibarbus yunnanensis Tsu in Lake Fuxian were investigated by examination of annuli from scales, dorsal fin spines, and otoliths. Sectioned otoliths exhibited the clearest and the most regular annuli. The formation of false annuli, which regularly arose on scales and dorsal fin spines during the juvenile stage, may be caused by a change in diet during development. The parameters for the von Bertalanffy growth curve were: K = 0.105, L∞ = 950 mm, t0 = −0.22 year for both sexes. W∞, calculated from the relationship W∞ = aL∞ b, was 10,352 g.

Reproductive strategy of a small endemic cyprinid, the Yarqon bleak (Acanthobrama telavivensis), in a mediterranean-type stream

A mediterranean-type climate exists in five widely separated regions; the Mediterranean basin, parts of western North America, parts of western and southern Australia, southwestern South Africa and parts of central Chile. Streams in these regions feature seasonal disturbances of contrasting hydrology with high predictability of the timing of flooding and drying but low constancy. We would expect fish living in these streams to avoid scouring flow and breed after cessation of the flood period. The aim of the present study was to examine the adaptation of the Yarqon bleak, Acanthobrama telavivensis, an endemic cyprinid in the coastal streams of Israel, to mediterranean-type stream (mediterranean—written with a small m, is used in connection with climate or ecological region and is distinguished from Mediterranean that is used in a geographical context, referring to the Mediterranean basin.) conditions. For that we studied its reproductive strategy (age at maturity and life span, gonad activity, oocyte maturation, spawning activity and habitats, appearance of juveniles), in a major costal stream (Yarqon). Our findings show that the Yarqon bleak exhibits life history traits attuned with a mediterranean-climate hydrologic regime. It breeds in late winter and early spring, a window of opportunity between flash floods and habitat desiccation. Being a multiple spawner allows the fish to compensate for the potential loss of part of its reproductive output due to scouring flows of late floods. The ability of the Yarqon bleak to spawn on different substrate-types enables it to take advantage of different stream conditions that pertain in different years. The fish attains pre-adult size (ca. 33–42 mm) within the first year, prior to drying out of most stream reaches, and matures by the beginning of the second year (males >41; females >42 mm). The cost of these tactics is a short life span (4–5 age groups). The reproductive strategy of the Yarqon bleak falls into the category of in-channel breeding but, unlike the case suggested by a low flow recruitment model, the fish breed during the period of flood cessation, a transitional time between high and low flows, rather than at the time of low flow. Breeding at this time of the year in mediterranean-type streams puts early stages somewhat at risk of being washed away by late floods, but gains them a longer period of growth under favorable conditions. We suggest an additional positive tradeoff that should be investigated: the reduced competition with age 0 of other fish that breed later in the season. This suggested model of recruitment during the period of flood cessation seems appropriate for fish in streams with seasonal contrasting flows of high predictability but low constancy.

Molecular evidence for the monophyly of East Asian groups of Cyprinidae (Teleostei: Cypriniformes) derived from the nuclear recombination activating gene 2 sequences

The family Cyprinidae is one of the largest families of fishes in the world and a well-known component of the East Asian freshwater fish fauna. However, the phylogenetic relationships among cyprinids are still poorly understood despite much effort paid on the cyprinid molecular phylogenetics. Original nucleotide sequence data of the nuclear recombination activating gene 2 were collected from 109 cyprinid species and four non-cyprinid cypriniform outgroup taxa and used to infer the cyprinid phylogenetic relationships and to estimate node divergence times. Phylogenetic reconstructions using maximum parsimony, maximum likelihood, and Bayesian analysis retrieved the same clades, only branching order within these clades varied slightly between trees. Although the morphological diversity is remarkable, the endemic cyprinid taxa in East Asia emerged as a monophyletic clade referred to as Xenocypridini. The monophyly for the subfamilies including Cyprininae and Leuciscinae, as well as the tribes including Labeonini, Gobionini, Acheilognathini, and Leuciscini, was also well resolved with high nodal support. Analysis of the RAG2 gene supported the following cyprinid molecular phylogeny: the Danioninae is the most basal subfamily within the family Cyprinidae and the Cyprininae is the sister group of the Leuciscinae. The divergence times were estimated for the nodes corresponding to the principal clades within the Cyprinidae. The family Cyprinidae appears to have originated in the mid-Eocene in Asia, with the cladogenic event of the key basal group Danioninae occurring in the early Oligocene (about 31–30 MYA), and the origins of the two subfamilies, Cyprininae and Leuciscinae, occurring in the mid-Oligocene (around 26 MYA).

Genetic analysis reveals two distinct Sacramento splittail (Pogonichthys macrolepidotus) populations

The Sacramento splittail is an endemic cyprinid fish of the San Francisco estuary and its tributaries, which is a highly manipulated, constantly changing ecosystem. Splittail is the only extant member of its genus and is listed as a federal and California Species of Special Concern due to uncertainties regarding long-term abundance trends. Determining population structure for splittail is important because unique populations may contain different adaptive genetic variation, which can allow one population to persist through future environmental or demographic stochasticity while others become extirpated. To assess splittail population structure, 13 microsatellite markers were used to genotype 489 young-of-year splittail from five major rivers draining into the estuary: Cosumnes, Napa, Petaluma, Sacramento, and San Joaquin Rivers. Two genetically distinct populations were found to exist within our study region; one largely comprised of splittail collected from the Petaluma and Napa Rivers and the second comprised of splittail collected from tributaries in Californiaȁ9s Central Valley: Cosumnes, Sacramento, and San Joaquin Rivers. These results were replicated in two consecutive years with both distance and model-based algorithms. The genetic distinction between these two populations appears correlated with salinity differences between migratory regions and spawning grounds. Splittail from the Petaluma River exhibited a significantly higher degree of differentiation from the Central Valley population than did Napa River splittail. Our results suggest on-going monitoring programs are probably highly biased towards sampling splittail from the Central Valley population. Understanding population dynamics of splittail could be improved if monitoring programs were expanded to include all splittail populations.

Rangewide molecular structuring in the Utah sucker (Catostomus ardens)

The Utah sucker (Catostomus ardens) is endemic to the Bonneville Basin and the upper Snake River drainage in western North America, and is thought to hybridize with the federally endangered June sucker (Chasmistes liorus mictus) in Utah Lake (Bonneville Basin). Here we describe the discovery of a major subdivision in Utah suckers (4.5% mitochondrial sequence divergence) between the ancient Snake River drainage and the Bonneville Basin. This boundary has not previously been recognized in Utah suckers based on morphologic variation, but has been recently described in two endemic cyprinids in the region. Populations in valleys east of the Wasatch Mountains in Utah clustered with the Snake River populations, suggesting that these valleys may have had an ancient hydrologic connection to the Snake River. We also found evidence of population isolation within the Bonneville Basin, corresponding to two Pleistocene sub-basins of the ancient Lake Bonneville. In contrast, we found no molecular evidence for deep divergence between Utah suckers and June suckers in Utah Lake or for a history of hybridization between divergent lineages in that population, although we recognize that demographic events may have obscured this signal. These findings suggest that the morphological differences between Utah and June suckers in Utah Lake may be the result of strong, and relatively recent, ecological selection. In summary, morphological and molecular characters seem to vary along different axes in different portions of the range of this taxon, providing an interesting system for studying the contributions of neutral and adaptive variation to species diversity.

Life History Traits of Ylikiensis Roach (Rutilus ylikiensis) in Two Greek Lakes of Different Trophic State

ABSTRACT The possible influence of trophic state on the life traits of a Greek endemic cyprinid fish (Rutilus ylikiensis) was investigated in two contrasting lakes. Lysimachia Lake is a eutrophic and very polluted shallow lake, while Trichonis Lake is an oligotrophic to mesotrophic, clearer, and deeper lake. Significant differences between the lakes were found in relation to the life history traits of the fish. In the eutrophic lake, fish achieved higher age and spawned more but smaller eggs than in the oligotrophic lake. In the eutrophic lake, females achieved higher age than males and the overall sex ratio of males: females was 1:3.42. The extrapolated mortality rate for females was significantly lower than that for males. Females were significantly heavier than males of the same length. In contrast to the above, no such differences between sexes were found in the oligotrophic lake.

AMMONIA TOXICITY TO JUVENILE ACANTHOBRAMA TELAVIVENSIS (CYPRINIDAE), A CRITICALLY ENDANGERED ENDEMIC FISH IN THE COASTAL PLAIN OF ISRAEL

We assessed the toxicity of ammonia to Acanthobrama telavivensis, a critically endangered endemic cyprinid that until the 1950s was very common in the coastal stream system, but is now restricted to a few unpolluted reaches. Ammonia toxicity was determined by a 96-h LC50 bioassay in a flow-through system with fish mortality as the end point. Acute toxicity of un-ionized ammonia for juvenile A. telavivensis is 1.00 mg l-1 NH3-N (0.94-1.06, 95% confidence limits), which corresponds to 20.1 mg l-1 total ammonia nitrogen at pH 8.0, total hardness of 250 mg/l (as CaCO3), and temperature of 24.2 °C. Acute-to-chronic ratio (ACR) values of 7.2, 10.9, and 16, suggested in the literature, yielded estimated safe ammonia concentrations for A. telavivensis of 0.14, 0.09, and 0.06 mg l-1 NH3-N, respectively, using the accelerated life testing (ALT) procedure. Accordingly, the 0.01% acceptable risk concentrations for 60 and 90 days are 0.17 and 0.16 mg l-1 NH3-N, respectively, agreeing with the safe ammonia concentratio...

Life history traits of Scardinius acarnanicus (Economidis, 1991) (Pisces: Cyprinidae) in two Greek lakes (Lysimachia and Trichonis)

Summary Age, growth, reproduction and mortality of Scardinius acarnanicus, an endemic cyprinid fish from central and western Greece, were investigated in two contrasting environments, the eutrophic Lake Lysimachia and the oligotrophic to mesotrophic Lake Trichonis. Maximum ages observed were 7+ for males and 10+ for females in Lake Lysimachia and 8+ for males and females in Lake Trichonis. Scardinius acarnanicus grew allometrically (slope of fork length–somatic weight regressions >3) and relatively rapidly until age 2 or 3 years, then slowed at a time coincident with maturation. Total instantaneous mortality rates of fish from Lake Trichonis were higher than in Lake Lysimachia. Scardinius acarnanicus is a multiple spawner; monthly values of the gonadosomatic index (GSI) indicated that spawning occurred mainly in April. Mean egg diameter in Lake Lysimachia was 1.54 ± 0.2 and 1.28 ± 0.16 mm in Lake Thrichonis. In Lake Lysimachia, the population sex ratio departed markedly from 1 : 1; females were more abundant at ages >3 and the overall male : female ratio was 1 : 1.47. In Lake Trichonis, females were more abundant at ages >6; the overall male : female ratio was 1 : 1.16, not significantly different from a 1 : 1 ratio.

Length at maturity and gillnet selectivity of Lake Tana's Barbus species (Ethiopia): Implications for management and conservation

Lake Tana's 15 large Barbus species form the only known intact endemic cyprinid species flock left in the world. The barbs contribute around one third of the total annual catch of the motorised commercial gillnet fishery which was introduced in 1986. A dramatic reduction of the adult Barbus stocks and the even lower proportion of recruits at the end of the 1990s, show the necessity for the development, implementation and control of fisheries legislation in Lake Tana. The reproductive biology of the Barbus species, essential for fishery management, is poorly known. This paper presents results on size at maturity, size at harvest and gillnet selectivity curves, which can be used to provide a scientific base for management proposals. Size at maturity varied widely among the Barbus species, ranging from 18.8 cm in Barbus brevicephalus to 44.3 cm in Barbus crassibarbis. Males matured at smaller size and reached smaller maximum length than females. Estimated selectivity curves fitted closely or were slightly larger than the observed length-frequency distribution of the commercial catch. The vast majority (85%) of barbs landed by the commercial gillnet fishery were mature. Fishing pressure on juvenile, immature fish is unlikely to be the cause of the observed decrease in Barbus stocks. Size control regulations like mesh size restrictions, intended to protect the immature part of fish populations are expected to have little positive effects on the Barbus stocks and are therefore not recommended. The drastic reduction in barbs during the 1990s is most like due to recruitment overfishing, that is, poorly regulated high fishing effort by the commercial gillnet fishery on the spawning aggregations of adult barbs during their annual breeding migration in river mouths and surrounding floodplains. Only effort control regulations limiting the gillnet fishery in the spawning season and/or areas will prevent a total collapse of the Barbus stocks as has happened to other cyprinids in African lakes. Such measures have to be implemented urgently to guarantee the conservation of Lake Tana's unique biodiversity as a sustainable source of cheap protein and as a natural laboratory to study the evolutionary processes underlying speciation in freshwater fish.

Interannual variation of fish assemblage structure in a Mediterranean river: implications of streamflow on the dominance of native or exotic species

AbstractStreams in mediterranean‐type climate regions are shaped by predictable seasonal events of flooding and drying over an annual cycle, but also present a strong interannual flow variation.The Guadiana River is one of the most important rivers in the Iberian Peninsula. The fish fauna presents 11 native freshwater species, including eight with high conservation status. Several exotic species are present, the most important being the American centrarchids pumpkinseed fish and largemouth bass. As a typical mediterranean‐type river, the Guadiana has an irregular hydrological regime with severe drought periods and floods; the interannual variation of discharge presents a ratio of c. 100 to 1.From 1980 to 1995 several dry years were observed, culminating in the drought of 19910/92–19947/95. Analysing the variation of the fish assemblage structure during this period, exotic species (mostly pumpkinseed) progressively increased, strongly dominating in 1995. Indigenous populations dramatically decreased and a previously common endemic cyprinid (Anaecypris hispanica Steindachner) became endangered and one of the most threatened fishes of Europe. However, the following years presented above‐average flows with several flood events and an inverse process occurred, with native species increasing their contribution in a short period.The importance of floods as a disturbance factor in the control of lentic or slow flowing water exotics is discussed. Native species apparently possess adaptive responses to high flows which exotics lack. This hypothesis is consistent with probability‐of‐use curves and preflood–postflood surveys. Results emphasize the importance of floods in the environmental flows of mediterranean‐type rivers. In the absence of flooding disturbance, exotic fish populations predictably grow, increasing the pressure on native species; abiotic disturbance may supersede deterministic outcomes of predation or competition and influence community structure by reducing populations of the exotic species. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Biology and Egg Morphology of The Dalmatian Barbelgudgeon Aulopyge Huegeli, An Endangered Endemic Species in Croatia

This paper describes patterns of annual and diurnal activity in the endangered endemic cyprinid Aulopyge huegeli from Croatia. The species is largely nocturnal. Spawning in the laboratory begins at temperatures of 20°C. Aulopyge huegeli is a rock and gravel brood hider. The female deposits eggs in various fissures with a special ovipositor. The eggs are whitish and have a diameter between 1.5 and 2 mm. The zona radiata is relatively thin (3.2–5.5 μm) and provides the eggs with the necessary plasticity. The surface is covered with an attaching substance and with short attachment extension around the vegetal pole. This correlates with features of the spawning microhabitats. Aulopyge huegeli has a very small micropyle which consists of a pit with a diameter of 7.5 μm and a canal with a diameter of 2.5 μm (micropyle type I).

River basin-related genetic structuring in an endangered fish species, Chondrostoma lusitanicum, based on mtDNA sequencing and RFLP analysis.

Chondrostoma lusitanicum is a Portuguese endemic cyprinid with a restricted distribution and reduced numbers in some basins, justifying its status as a threatened species. We examined genetic population structure using samples from throughout its geographical range in Portugal, using sequencing of b cytochrome and restriction fragment length polymorphism analysis of the NADH subunits 5 and 6. There was reduced within-population genetic variability but considerable among-population differentiation, particularly marked between both the Mira and Arade basins in the extreme south and other populations. These results confirm phylogeographic relationships suggested by previous fragmentary allozyme studies for C. lusitanicum, and are in accordance with allozyme and mitochondrial DNA data on phylogeography of coexisting cyprinid species of the genus Leuciscus. The levels of genetic divergence revealed by sequence and RFLP data showed strongly concordant patterns: geographical genetic structuring, with the definition of three distinct groups, was observed. The high values of nucleotide divergence and pairwise sequence divergence of the Mira and Arade groups, when compared with all other samples, support a distinct taxonomic status probably at the species level. Results are also discussed in relation to conservation of this highly fragmented species, in terms of Evolutionary Significant Units and Management Units.

Barbus tanapelagius, A New Species from Lake Tana (Ethiopia): its Morphology and Ecology

The endemic cyprinid species flock in Lake Tana consists of 15 species of large hexaploid barbs, eight of which are piscivorous. Previously, it was assumed that all piscivores preyed on the same small barb species, Barbus trispilopleura. In this paper we present a description of morphology and ecology of a new abundant small barb species, Barbus tanapelagius sp. nova (holotype RMNH 33731) from Lake Tana, Ethiopia, which appears to be the major prey species for the large pelagic piscivorous barbs. B. tanapelagius differs clearly in morphology from the other 3 small, diploid Barbus species known from Lake Tana, B. trispilopleura Boulenger, 1902, B. humilis Boulenger, 1902 and B. pleurogramma Boulenger, 1902. Conspicuous differences are its elongated body, large eye diameter, prominent and hooked lower jaw contour and colouration. Preliminary data suggest that B. tanapelagius also differs ecologically from the other small Barbus spp. by its pelagic, strictly zooplanktivorous feeding and its occurrence mainly in the deeper, offshore waters. The other small Barbus species are most probably largely benthic feeders and dominant in the shallow inshore waters. Previous views about the evolution of the present 8 endemic piscivorous large barb species therefore require reconsideration, as the present paper shows a more complex scenario including several prey species.

Congruence between allozyme and cytochrome b gene sequence data in assessing genetic differentiation within the Iberian endemic Chondrostoma lemmingii (Pisces: cyprinidae).

To understand further the fragmentation of the hydrographical basins and the processes of divergence and speciation of freshwater fishes of the Iberian Peninsula, 10 populations of the Iberian endemic cyprinid Chondrostoma lemmingii were studied using 26 loci encoding 19 enzymes and the complete nucleotide sequence of the mitochondrial cytochrome b gene. Nuclear and mitochondrial DNA markers showed complete congruence in assessing the genetic differentiation among the samples analysed. This congruence was supported by a Mantel test in which a significant correlation (r=0.89) between Nei's genetic distances and sequence divergence (uncorrected p distances) was obtained. Diagnostic loci, Nei's genetic distances, and FST values, as well as the percentage of sequence divergence indicate that the Duero basin population accumulates the highest level of genetic differentiation. A moderate divergence was also observed among populations of the rest of the basins. Phenetic and phylogenetic relationships support the hypothesis that the differentiation process was not only due to hydrographical basin isolation but also due to an ancient endorrheism event, previous to hydrographical configuration, that could explain the marked differentiation of the Duero basin population.

Mitochondrial DNA differentiation in the critically endangered Berg River redfin (Pseudobarbus burgi).

The Berg River redfin (Pseudobarbus burgi) is a critically endangered endemic cyprinid from South Africa. We investigated mitochondrial DNA control region variation among specimens representative of five populations drawn from two adjacent river systems. Phylogenetic analyses, a minimum spanning network, and an analysis of molecular variance underscore the pronounced genetic separation of redfins originating from the geographically closely allied Verlorevlei and Berg Rivers, two populations that may have remained isolated since the Pleistocene. Despite a lack of geographic structuring within the Berg River, historic female gene flow among the upper and middle/lower parts of the river appears to be limited and the contemporary populations are probably isolated due to deterioration of the mainstream of the river. Our results suggest that the Berg and Verlorevlei populations should be managed as distinct conservation units. We encourage the use of sanctuaries, particularly by private landowners within both river systems, as this approach may contribute effectively to preserving genetic diversity within the species.