Species Oreochromis Research Articles

Analysis of the pharyngeal structure of the genus Oreochromis for species identification through geometric morphometrics in the Aguamilpa reservoir, Nayarit, Mexico

Tilapia is an important fishing resource in economic terms for continental ecosystems such as dam reservoirs and lagoons. In Nayarit, the Aguamilpa Dam reservoir contributes around 50 % of the tilapia production in the state. However, despite the social and economic importance of the resource, there are few studies on it in this reservoir, and it is still unknown with certainty which species are found in the reservoir. This work is the first report for the Aguamilpa reservoir, where geometric morphometrics was used as a tool for the identification of tilapia species. The pharyngeal plate of 230 organisms was used for the geometric morphometrics analysis. According to this study, the existence of three species of the genus Oreochromis (O. aureus, O. niloticus and Oreochromis mossambicus) is confirmed; according to the analysis of canonical variables, the three species were correctly discriminated. This allows us to conclude that the use of geometric morphometrics in the pharyngeal plate is a useful structure for the identification of species in the reservoir.

Genetic diversity and population dynamics of wild Mozambique tilapia (Oreochromis mossambicus) in South Africa

Urbanisation and water developments in South Africa have created numerous challenges in managing water resources. Consequently, the native fish species Oreochromis mossambicus, prominent to freshwater ecosystems in South Africa now faces the threat of extinction amidst introductions of alien Oreochromis species. The species has recently been classified as Vulnerable on the IUCN Red List. Despite the economic importance of O. mossambicus within the South African region, little is known about the genetic and population dynamics of the species. In this study, we aimed to establish baseline genetic and population data, and determine the impact of water management practices on population structure. This data is crucial for the conservation and monitoring of this species across South Africa. The study revealed relatively low genetic diversity within sample localities but significant differentiation among populations. The analyses identified 16 geographically correlated genetic clusters, indicating substantial differentiation across catchments. Anthropogenic activities, changes in catchment use, and water management strategies significantly influenced the genetic population structure in the studied regions. Given the distinct genetic patterns, conservation-oriented management should prioritise maintaining existing genetic diversity to ensure the long-term survival of this vulnerable species.

Escapes from aquaculture facilities in freshwater ecosystems; conservation concerns for Oreochromis tanganicae, an endemic species of Lake Tanganyika

Introduction of farmed non-native fish strains into ecosystems outside their native range has raised global concerns. We investigate the presence of Oreochromis niloticus in the southernmost part of Lake Tanganyika. DNA was extracted from tissue samples and analysed using microsatellite DNA markers. We confirm the O. niloticus from the observed morphological features of the samples collected and the analysis using genetic markers. Although the species is native to the lake, it is unclear if the fish now being sampled are indigenous or escaped from aquaculture facilities 15–20 years ago. The genetic diversity was similar statistically, though higher in O. tanganicae, followed by wild O. niloticus and least in farmed O. niloticus. There was no evidence of hybridisation between O. niloticus and native O. tanganicae. We recommend a comprehensive investigation to ascertain the origin of the O. niloticus, which, though rare, is present in catches. Due to known introductions, conservation measures must be set up to protect the genetic purity of O. tanganicae since O. niloticus is known to hybridise with other Oreochromis species and it is not known whether the farmed non-native strain is capable to establish such hybridization more than the wild native strain.

Introgressive hybridization levels of Tilapiine species in Lake Victoria basin, Kenya inferred from microsatellite and mitochondrial DNA genotyping based on next-generation sequencing

Despite their high abundance and species richness, tilapiines have been compromised by various factors especially overfishing, climate change, and uncontrolled fish transfers and introductions. Fish introductions have negatively impacted native tilapiine populations through competition, predation, hybridization, and introgression compromising their genetic integrity. The hybridization levels of different tilapiines in the Lake Victoria basin remain relatively understudied. The study utilized nuclear microsatellite and mitochondrial DNA (mtDNA) genetic markers to investigate hybridization signals and compare the genetic diversity of different tilapiines in Lake Victoria, Kenya, using next-generation sequencing. Low levels of hybridization from Oreochromis niloticus into other Oreochromis species were detected by Bayesian clustering analysis and principal coordinate analysis (PCoA). The results contribute to the need for conservation measures for these fish species.

The Assessment of the Toxic Effects of Bisphenol A (BPA) on Physiology and Reproduction of the Fish Species Oreochromis mossambicus

The industrialized world produces massive amounts of plastic every year. Recent research information suggests that BPA exhibits hormone-like properties, raising concerns about its suitability in some consumer products and food containers. The most important human exposure route to BPA is diet, which includes consumption of unclean food and water. Exposure to BPA has resulted in adverse effects on reproduction, embryonic development, and the onset of genetic abnormalities in both aquatic and terrestrial animals. However, reports of the effects of BPA on reproductive physiology in fish are limited. This study was aimed to study the adverse effect of BPA on the regulation of reproductive genes in Mozambique tilapia (Oreochromis mossambicus) fish species. The tissue distribution patterns of GnRH1 and GnRH1 in adult Oreochromis mossambicus are shown in predominantly expressed in brain tissues but after the exposure of BPA the gene expression were reported down regulated. When t test was applied on the obtained data we have reported the statically significant down regulation of the GnRH2 (t test P = 0.0395) after the exposure of BPA 5mg BPA/L. This study showed the adverse effect on the reproductive genes of the Oreochromis mossambicus.

Phenotypic and genotypic comparison of pathogenic group B Streptococcus isolated from human and cultured tilapia (Oreochromis species) in Malaysia

Group B Streptococcus (GBS) is a major cause of several infectious diseases in humans and fish. This study was conducted to compare human and fish-derived GBS in terms of their antimicrobial susceptibility, serotype, virulence and pili genes and sequence type (ST), and to determine whether there is a potential linkage of zoonotic transmission in Malaysia. GBS isolated from humans and fish had similar phenotypic characteristics and differed in virulence gene profile, antimicrobial susceptibility, serotype and sequence type. Fish GBS isolates had lower genetic diversity and higher antibiotic susceptibility than human isolates. We report a rare detection of the potentially fish-adapted ST283 in human GBS isolates. Both human and fish ST283 shared several phenotypic and genotypic features, including virulence and pilus genes and antimicrobial susceptibility, illustrating the value of monitoring GBS within the One Health scope. In this study, two human GBS ST283 isolates belonging to the variant common in fish hosts were identified, raising awareness of the zoonotic potential between the different species in Malaysia.

Epidemiology of epizootic ulcerative syndrome (EUS) in fish in the main water bodies of the Kavango–Zambezi and Great Limpopo transfrontier conservation areas of Zimbabwe

A three-year study investigated the epidemiology of epizootic ulcerative syndrome (EUS) in fish from Kavango-Zambezi (KAZA) and Great Limpopo (GL) transfrontier conservation areas of Zimbabwe. A total of 38 sites comprising 27 wild fisheries and 11 aquacultures, from Mashonaland West, Matabeleland North and South, and Midlands were selected. Of the 27 wild fisheries, EUS-positive fish were detected from 9 (33.3%) and none from the 11 aquacultures. No positive cases were detected from Nile tilapia (Oreochromis niloticus) from both aquacultures and wild fisheries. A total of 9.9% (239/2423) fish from the nine positive fisheries had typical EUS lesions, and infection was confirmed in 15 species. Prevalence was significantly higher (p < 0.05) in KAZA (11.5%; 95% CI: 9.6-13.4) compared with GL (8.6%; 95% CI: 7.1-10.1). The most affected were Clarias, followed by Barbus and Oreochromis species. Most cases (>80%) were reported in winter when ambient temperature was low. Further studies are required to determine water parameters associated with EUS outbreaks. These results suggested that the African sharptooth catfish (Clarias gariepinus) could be used potentially as an indicator species for EUS surveillance programmes. Thus, implementation of surveillance and biosecurity programmes that take into consideration the epidemiology of EUS will be beneficial.

Towards a DNA barcode library for Madagascar's threatened ichthyofauna.

In order to improve the molecular resources available for conservation management of Madagascar’s threatened ichthyofauna, we elaborated a curated database of 2860 mitochondrial sequences of the mitochondrial COI, 16S and ND2 genes of Malagasy fishes, of which 1141 sequences of freshwater fishes were newly sequenced for this data set. The data set is mostly composed of COI (2015 sequences) while 16S and ND2 sequences from partly the same samples were used to match the COI sequences to reliably identified reference sequences of these genes. We observed COI uncorrected pairwise genetic distances of 5.2‒31.0% (mean 20.6%) among species belonging to different genera, and 0.0‒22.4% (mean 6.4%) for species belonging to the same genus. Deeply divergent mitochondrial lineages of uncertain attribution were found among Malagasy freshwater eleotrids and gobiids, confirming these groups are in need of taxonomic revision. DNA barcodes assigned to introduced cichlids (tilapias) included Coptodon rendallii, C. zillii, Oreochromis aureus (apparently a new country record), O. cf. mossambicus, O. niloticus, and one undetermined species of Oreochromis, with sequences of up to three species found per location. In aplocheiloid killifishes of the genus Pachypanchax, most species from northern Madagascar had only low mitochondrial divergences, three of these species (P. omalonotus, P. patriciae, and P. varatraza) were not reciprocally monophyletic, and one genetically deviant lineage was discovered in a northern locality, suggesting a need for partial taxonomic revision of this genus. While the lack of voucher specimens for most of the samples sequenced herein precludes final conclusions, our first step towards a DNA barcoding reference library of Madagascar’s fishes already demonstrates the value of such a data set for improved taxonomic inventory and conservation management. We strongly suggest further exploration of Madagascar’s aquatic environments, which should include detailed photographic documentation and tissue sampling of large numbers of specimens, and collection of preserved voucher specimens as well as of living fish for the buildup of ex situ assurance populations of threatened species complying with the One Plan Approach proposed by the IUCN SSC Conservation Breeding Specialist Group (CBSG).

Are Fish Markets in Central Malawi Profitable and Efficient? Performance of Diploxatodon spp. (Ndunduma) Markets in Salima and Lilongwe Districts

The production of underexploited small fish species has surpassed that of bigger and more valuable species, such as Oreochromis species. However, profitability and efficiency of the key players in the marketing chain and system associated with these small fish species are yet to be understood. Therefore, this article aims to analyze the profitability and efficiency of Diplotaxodon spp. (an example of a small fish species) fish marketing systems in Malawi. The analysis was based on data collected in 2019 through field surveys from 265 respondents, which included fishers, processors, wholesalers, and retailers. Gross margin, return on capital employed (ROCE), and the Acharya and Agarwal’s market efficiency index were used in our empirical strategy. The results reveal that Diplotaxodon spp. trading was profitable to all actors. Firm-level efficiency showed that all actors used their capital efficiently, except for fishers, who had lowest return on capital employed, while retailers had the highest return on capital employed. All marketing channels identified were inefficient, due to high marketing margins and low fisher’s share of the consumer price, attributed to high transportation cost. The study concludes that, unless efforts are taken to improve efficiency of Ndunduma marketing system, through improving marketing margins and fisher’s share of consumer price, Diplotaxodon spp. will continue to be under-exploited, thereby sustaining or exacerbating the fish supply gap.

Dietary Strategies for Better Utilization of Aquafeeds in Tilapia Farming

Feed management practices significantly impact the production performance of tilapia (Oreochromis species) culture economically; hence, adopting appropriate feed management strategies is vital to maximize returns. The advancement in aquaculture has also allowed an advancement in the development formulated feeds to supplement or replace natural feeds. Farmers are now able to prepare their own fish feeds from locally available ingredients. Hence, feed ingredient evaluation is crucial for better development of appropriate diets for different aquaculture species as well as nutritional research. Therefore, this review used secondary data to evaluate the different strategies employed for better utilization of nutrients in feed by providing a discussion of functional feed additives used in aquafeeds such as the addition of enzymes, pre/probiotics, feeding stimulants, and use of hormones. Supplementation of diet with xynalase and phytase enzymes ( P &lt; 0.001 ) and probiotics ( P &lt; 0.05 ) improved growth (g/d) and FCR when applied individually. The combination of enzymes and probiotics showed an interaction effect ( P &lt; 0.05 ) on growth and FCR. A detailed discussion of feed ingredient processing strategies like fermentation, heat treatment, germination, and other biological methods meant to improve the nutritional quality of the feed and minimize antinutritional factors is provided. Furthermore, information on how genetic selection is being used to enhance feed utilization in tilapia fish is provided. The food conversion efficiency was found to be significantly higher ( P &lt; 0.05 ) in transgenic tilapia compared to the nontransgenic red tilapia fish with average weight ± SD of 384 ± 158 g and 314 ± 101 for transgenic fish and red tilapia, respectively, after 275 days of culture. The review further outlines the feed formulation challenges, and research gaps in tilapia nutrition. It was noted that proper feeding management strategies are very critical for the sustainability of tilapia aquaculture. In conclusion, dietary sources for tilapia are slowly shifting to plant-based products. However, these come with a lot of antinutritional factors and digestibility problems; hence, the right feeding strategies have to be employed to enable efficient nutrient utilization. The review discovered that there are a lot of strategies which employed research gaps in tilapia nutrition, especially on nutrient utilization of feed and feed formulation.

Identifikasi dan Analisis Filogenetik Ikan Ekonomis Penting Oreochromis sp. dengan Pendekatan DNA Barcoding

Species identification is one of the most basic and important factors in fisheries management. Oreochromis sp., such as tilapia (Oreochromis mosambicus) and tilapia (Oreochromis niloticus) are introduced species of fish originating from outside Merauke which are now the dominant fish and are commonly found in inland waters of Merauke. The purpose of this study was to identify the economically important fish species Oreochromis sp. which landed at Merauke Traditional Market with DNA Barcoding approach. DNA amplification with the COI gene resulted in a DNA sequence length of 655 bp with the identification result being Tilapia (Oreochromis niloticus). Based on the phylogenetic tree data and genetic distance, the DNA sequences of the samples formed the same clade as the Oreochromis niloticus sequences from GeneBank with 0% genetic distance and it was estimated that these species came from the same parents. Identification with DNA Barcoding makes it easy to identify species quickly and accurately.

Whole genome resequencing data enables a targeted SNP panel for conservation and aquaculture of Oreochromis cichlid fishes

Cichlid fish of the genus Oreochromis form the basis of the global tilapia aquaculture and fisheries industries. Broodstocks for aquaculture are often collected from wild populations, which in Africa may be from locations containing multiple Oreochromis species. However, many species are difficult to distinguish morphologically, hampering efforts to maintain good quality farmed strains. Additionally, non-native farmed tilapia populations are known to be widely distributed across Africa and to hybridize with native Oreochromis species, which themselves are important for capture fisheries. The morphological identification of these hybrids is particularly unreliable. Here, we describe the development of a single nucleotide polymorphism (SNP) genotyping panel from whole-genome resequencing data that enables targeted species identification in Tanzania. We demonstrate that an optimized panel of 96 genome-wide SNPs based on FST outliers performs comparably to whole genome resequencing in distinguishing species and identifying hybrids. We also show this panel outperforms microsatellite-based and phenotype-based classification methods. Case studies indicate several locations where introduced aquaculture species have become established in the wild, threatening native Oreochromis species. The novel SNP markers identified here represent an important resource for assessing broodstock purity in hatcheries and helping to conserve unique endemic biodiversity.

Notes on the Distribution of the Genus Oreochromis in the East Mediterranean Region of Turkey

Tilapias are freshwater species which are the common name of three genera of cichlids, Oreochromis, Sarotherodon, and Coptodon . Many of the species belonged to these genera have been used for aquaculture products. Although their main native distribution areas are tropical and subtropical regions, they have spread to other areas due to their high invasive characteristics. This study was aimed to investigate the distribution of genus Oreochromis in the East Mediterranean Region of Turkey. The study was conducted at 18 stations located in Adana and Mersin from 2014 to 2017. The introduction of the species in these systems was mainly recorded weed control, transfers of fisherman, and escape from aquaculture facilities. However, the distribution of genus Oreochromis in Turkey and their effects on the aquatic ecosystems are unknown. The results showed that the species of genus Oreochromis were easily adapted the different conditions such as various flow rates, salinity, and temperature.

Testing for hybridization between Nile tilapia (Oreochromis niloticus) and blue spotted tilapia (Oreochromis leucostictus) in the Lake Edward system

Oreochromis is the most important tropical freshwater fish genus for aquaculture purposes, with various introduction and translocation events having played an integral part of its management. Some Oreochromis species such as the Nile tilapia, O. niloticus, are thought to be superior for aquacultural purposes when compared to other species. Hence, understanding the admixed nature of the species within a native system is of key importance for the development of future broodstock. Using a combination of mitochondrial (COI) and nuclear (microsatellites) DNA, we tested for the presence of O. niloticus and O. leucostictus hybrids within the Lake Edward-George system. The present study revealed that, despite their natural overlapping ranges, hybridization between O. niloticus and O. leucostictus appears to be rare within the Lake Edward-George system, suggesting that the native populations of these two species may serve as suitable broodstock to develop future aquaculture strains. Moreover, our study provides the first COI sequences for O. leucostictus from its native range and adds to the growing database of O. niloticus sequences.

Uncovering endemism in a lake of invasive species introgression.

Species distributions are rapidly being altered by human globalisation and movement. As species are moved across biogeographic boundaries, human-mediated secondary contacts between historically allopatric taxa may promote hybridisation between closely related native and introduced species. The outcomes of hybridisation are diverse from strong reproductive barriers to gene flow to genome-wide admixture that may enhance (Fitzpatrick et al., 2010; Mesgaran et al., 2016; Valencia-Montoya et al., 2020) or impede (Kovach et al., 2016) invasive spread. For native species, introgressive hybridisation may disassemble locally adapted genomes, and in extreme cases, extensive asymmetric introgression may lead to the 'genomic extinction' of endemic diversity (Rhymer & Simberloff, 1996; Todesco et al., 2016). Undoubtedly, introgressive hybridisation can rapidly alter the evolution of introduced and endemic populations. This is a major conservation issue (Leitwein, Duranton, Rougemont, Gagnaire, & Bernatchez, 2020), with the greatest potential consequences on small, range-restricted native populations where introduced species may reach higher relative densities (Currat, Ruedi, Petit, & Excoffier, 2008). In this issue of Molecular Ecology, Blackwell et al. (2020) explore the history of divergence and admixture between the highly invasive Nile tilapia, Oreochromis niloticus, and a recently discovered Oreochromis lineage that is endemic to the coastal lakes of southern Tanzania. Oreochromis tilapias belong to the African cichlids and the most diverse family of vertebrates (Cichlidae), with almost 2000 species inhabiting the Great Lakes and river environments of Eastern Africa (Kocher, 2004; McGee et al., 2020). By analysing previously unrecognised cichlid diversity from southern lakes, Blackwell et al. (2020) provide novel evidence for how introgressive hybridisation with introduced species can alter native genetic makeup, illustrating the potential susceptibility of Tanzania's endemic biodiversity to genetic threats from introduced taxa.

Risk Assessment of Some Heavy Metals in Two Fish Species Oreochromis Niloticus and Clarias Gariepinus from Sharqia Province, Egypt

Accumulation of heavy metals in fish is considered a critical problem for human health. Therefore, the study aimed to quantify the concentrations of iron (Fe), zinc (Zn), manganese (Mn), and lead (Pb) in Oreochromis niloticus and Clarias gariepinus from two areas in Al Sharqia governorate, Egypt, from September 2017 to August 2018. A human health risk assessment was conducted to evaluate the potential hazards associated with fish consumption. Metals concentrations (mg/kg dry weight) in muscles of catfish ranged 1.88-221.26 for Fe; 1.78-19.77 for Zn; BDL-238.51 for Mn; BDL-22.75 for Pb. In muscles of tilapia fish metals concentrations ranged 7.96-149.10 for Fe; 1.20-19.77 for Zn; BDL-230.82 for Mn; BDL-25.93 for Pb. Pb had Hazard quotients (HQs) which indicated potential health risks to tilapia consumers at both study areas and catfish consumers at the Faqous area. Fishermen were at higher risk compared to the other consumers.

Utility of DNA barcoding in native Oreochromis species.

The importance of Oreochromis in worldwide aquaculture and regional fisheries motivates the study of their genetic diversity in their native range. In this article, all mitochondrial cytochrome c oxidase subunit I gene (COI) sequences of Oreochromis species are retrieved from Barcode of Life Data system to quantify the available DNA barcoding information from wild individuals collected within the native ranges of the respective species. It is found that 70% of the known species in the genus still lack a COI barcode, and only 15% of the available sequences are from within the respective native ranges. Many of the available sequences have been produced from specimens acquired from aquaculture and introduced, naturalized populations, making the assessment of variation within the original native range challenging. Analyses of the wild-collected fraction of available sequences indicated the presence of cryptic lineages within Nile tilapia Oreochromis niloticus and O. schwebischi, the occurrence of potential introgressive hybridization between O. niloticus and blue tilapia O. aureus, and potential ancestral polymorphism between Karonga tilapia O. karongae and black tilapia O. placidus. This article also reports a case of misidentification of O. mweruensis as longfin tilapia O. macrochir. These results stress the importance of improving the knowledge of genetic variation within the native ranges of Oreochromis species for better-informed conservation of these natural resources.

Acusicola margulisae n. sp. (Copepoda: Ergasilidae) from freshwater fishes in a Nicaraguan crater lake based on morphological and molecular evidence.

The ergasilid copepod Acusicola margulisae n. sp. is described based on material from three species of cichlid, Amphilophus citrinellus (Günther), Parachromis managuensis (Günther), and Oreochromis sp., and from the poecilid Poecilia mexicana (Steindachner), in the crater Lake Asososca León, Nicaragua. This constitutes the 15th species described in the genus Acusicola Cressey, 1970. The new species differs from all its congeners by the relatively longer first endopodal segment of leg 1, and the size and number of setae on second endopodal segment of leg 1. We provide the first gene sequence for a species of Acusicola. To examine the intraspecific genetic variation of the new species collected from different host species, sequences of the mitochondrial barcode region cox1 were generated. In addition, partial regions of the 18S and 28S ribosomal RNA genes were sequenced and used to infer the phylogenetic relationships of the genus Acusicola within the family Ergasilidae Burmeister, 1835. The phylogenetic trees yielded the isolates of Acusicola margulisae n. sp. as a reciprocally monophyletic lineage, and as the sister taxa of five genera of ergasilid copepods. The genus Ergasilus von Nordmann, 1832 was recovered as a paraphyletic group. These analyses indicate that phylogenetic relationships are not yet well resolved and more representative species and genera of the family are required to provide a robust classification of this highly diverse group of copepods.

Molecular phylogeny of Oreochromis (Cichlidae: Oreochromini) reveals mito-nuclear discordance and multiple colonisation of adverse aquatic environments

Although the majority of cichlid diversity occurs in the African Great Lakes, these fish have also diversified across the African continent. Such continental radiations, occurring in both rivers and lakes have received far less attention than lacustrine radiations despite some members, such as the oreochromine cichlids (commonly referred to as ‘tilapia’), having significant scientific and socio-economic importance both within and beyond their native range. Unique among cichlids, several species of the genus Oreochromis exhibit adaptation to soda conditions (including tolerance to elevated temperatures and salinity), which are of interest from evolutionary biology research and aquaculture perspectives. Questions remain regarding the factors facilitating the diversification of this group, which to date have not been addressed within a phylogenetic framework. Here we present the first comprehensive (32/37 described species) multi-marker molecular phylogeny of Oreochromis and closely related Alcolapia, based on mitochondrial (1583 bp) and nuclear (3092 bp) sequence data. We show widespread discordance between nuclear DNA and mitochondrial DNA trees. This could be the result of incomplete lineage sorting and/or introgression in mitochondrial loci, although we did not find a strong signal for the latter. Based on our nuclear phylogeny we demonstrate that adaptation to adverse conditions (elevated salinity, temperature, or alkalinity) has occurred multiple times within Oreochromis, but that adaptation to extreme (soda) conditions (high salinity, temperature, and alkalinity) has likely arisen once in the lineage leading to O. amphimelas and Alcolapia. We also show Alcolapia is nested within Oreochromis, which is in agreement with previous studies, and here revise the taxonomy to synonymise the genus in Oreochromis, retaining the designation as subgenus Oreochromis (Alcolapia).

Recurrent changes in cichlid dentition linked to climate‐driven lake‐level fluctuations

AbstractClimate‐induced habitat change has often been invoked as an important driver of speciation and evolutionary radiation in cichlid fishes, yet studies linking morphological change directly to long‐term environmental fluctuations are scarce. Here, we track changes through time in the oral dentition of Oreochromis hunteri, the endemic and only indigenous fish species inhabiting the East African crater Lake Chala (Kenya/Tanzania), in relation to climate‐driven lake‐level fluctuations during the last 25,000 yr. Fossil teeth were recovered from six periods representing alternating high and low lake‐level stands associated with late‐Pleistocene and Holocene trends in rainfall and drought. To construct a reference framework for morphological variation in fossil assemblages, we first analyzed the variability in oral tooth morphology within the modern‐day fish population. These analyses established that, like other cichlids, O. hunteri gradually replace their bicuspid/tricuspid oral dentition with more unicuspid teeth as they grow. In the fossil assemblages, we found systematic and recurrent changes in the relative abundance of these oral tooth types, with a higher proportion of unicuspids during low‐stands. Moreover, O. hunteri living during low‐stands systematically developed unicuspid dentition at a smaller body size, compared with conspecifics living during high‐stands. Considering that low‐stand conditions created a sizable area of oxygenated soft‐bottom habitat that is lacking during high‐stands, we propose that the associated change in oral dentition reflects the fishes’ exploitation of this new habitat either for feeding or for reproduction. The recurrent nature of the observed shifts provides evidence for the ability of O. hunteri to systematically adapt to local habitat change, and strongly suggests that morphological change in oral dentition promoted its long‐term population persistence in an aquatic ecosystem presenting the dual challenge of being both sensitive to climate change (creating constantly shifting selective pressures) and isolated from surrounding populations (limiting gene flow). In Lake Chala, ancient climate‐driven lake‐level fluctuations did not directly promote speciation in O. hunteri, but the population bottlenecks they may have caused potentially contributed to its divergence from sister species Oreochromis jipe.