MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

https://doi.org/10.47193/mafis.3712024010107

ABSTRACT. The presence of the non-native Nile perch (Lates niloticus) in Lake Victoria and

the resulting ecological transformations have garnered significant attention from the scientific com-

munity. However, details regarding the timing, origin, and purpose of the fish introduction have

remained elusive. This paper reviews fish fauna changes in Lake Victoria, investigates causes, and

advocates for biodiversity conservation through diversity and sanctuary sites. It examines different

historical periods to understand changes and guide effective conservation strategies. The introduc-

tion of Nile perch has led to a substantial decline and even extinction of many native fish species,

particularly cichlids, resulting in ecological imbalances and economic challenges for local fishing

communities. To address these pressing issues, ongoing conservation efforts are being implemented.

These initiatives focus on promoting sustainable fishing practices, safeguarding critical habitats, and

reintroducing native fish species. Furthermore, cage fish farming is being explored as a potential

solution to alleviate pressure on wild populations, as suggested by various authors. Recommenda-

tions stemming from this study include conducting virtual population analysis for stock assessments

of indigenous species, intensify conservation efforts, diversify fishing practices, expand cage fish

farming, increase public awareness and education, and enhance policy and governance frameworks.

By implementing these recommendations, there is optimism for the recovery and resilience of

indigenous fish species in Lake Victoria, leading to the conservation of biodiversity and the promo-

tion of sustainable livelihoods for local communities.

Key words: Nile perch, extinction, invasive species, African cichlids, exotic species introductions.

Esplendor en desaparición: una revisión exhaustiva de la disminución de la fauna de peces

original del Lago Victoria

RESUMEN. La presencia de la perca del Nilo (Lates niloticus) exótica para el Lago Victoria y

las transformaciones ecológicas resultantes, han generado una atención significativa por parte de

la comunidad científica. Sin embargo, los detalles sobre el momento, el origen y el propósito de

la introducción del pez siguen siendo difíciles de dilucidar. Este artículo analiza los cambios en la

fauna de peces en el Lago Victoria, investiga las causas y aboga por la conservación de la biodi-

versidad a través de la diversidad y los santuarios. Examina diferentes períodos históricos para

comprender los cambios y guiar estrategias de conservación efectivas. La introducción de la perca

del Nilo ha provocado una disminución sustancial e incluso la extinción de muchas especies de

peces nativos, en particular de cíclidos, lo que ha provocado desequilibrios ecológicos y desafíos

económicos para las comunidades pesqueras locales. Para abordar estos problemas apremiantes,

se están implementando esfuerzos de conservación continuos. Estas iniciativas se centran en pro-

209

*Correspondence:

juma.syanya@cusat.ac.in

Received: 9 August 2023

Accepted: 15 September 2023

ISSN 2683-7595 (print)

ISSN 2683-7951 (online)

https://ojs.inidep.edu.ar

Journal of the Instituto Nacional de

Investigación y Desarrollo Pesquero

(INIDEP)

This work is licensed under a Creative

Commons Attribution-

NonCommercial-ShareAlike 4.0

International License

Marine and

Fishery Sciences

MAFIS

REVIEW

Vanishing splendor: a comprehensive review of the decline in the original

fish fauna of Lake Victoria

FREDRICK JUMA SYANYA1, *, ZACHARY O. WINAM2and WILSON M. MATHIA2

1School of Industrial Fisheries (SIF), Cochin University of Science and Technology (CUSAT), Foreshore Road, Ernakulam, India.

2Government of Kenya Ministry of Agriculture Livestock and Fisheries, Nairobi, Kenya.

ORCID Fredrick Juma Syanya https://orcid.org/0000-0001-8728-8614, Zachary O. Winam https://orcid.org/0009-0007-2089-918X,

Wilson M. Mathia https://orcid.org/0000-0002-3986-6384

INTRODUCTION

Lake Victoria, a freshwater lake shared by the

eastern African countries of Kenya, Uganda, and

Tanzania, is one of the largest tropical freshwater

lake globally, covering a vast surface area of

68,900 km2(Okedi 1990). Unlike other notable

lakes in eastern Africa, it stands out with its rela-

tively shallow maximum depth ranging from 70

to 80 m (Njiru et al. 2018). The lake is renowned

for its remarkable fish species diversity, with hap-

lochromine cichlids and the introduced Nile

perch (Lates niloticus) being dominant (Witte et

al. 2007a). However, the past century has wit-

nessed significant human-induced changes in the

ecosystem of Lake Victoria (Hecky et al. 2010)

with activities such as fishing, species introduc-

tions, and eutrophication having substantial

impacts on the fish fauna.

Prior to the introduction of Nile perch, Lake

Victoria boasted a diverse array of fish species,

including Haplochromine spp., Labeo victori-

anus,Propterus ethiopicus,Brycinus spp., Bar-

bus spp., Momyrus kanume, omena (Rastaneobo-

la angentinea), and Synodontis victorianus,

which served as an affordable source of protein

for local communities along the lake’s shorelines

of Kenya, Tanzania, and Uganda (Katunzi 2003;

Njiru et al. 2014). The unique nature of these fish

populations attracted the global attention of biol-

ogists and taxonomists, contributing significantly

to scientific research into Lake Victoria fisheries.

However, the rapid growth of the human popu-

lation around Lake Victoria basin has brought var-

ious socioeconomic demands, such as the expan-

sion of agricultural land, landing sites, cage farm-

ing, industrialization and urbanization (Onyango

et al. 2021). Consequently, severe environmental

degradation has occurred, primarily due to sedi-

ment pollution from unsustainable agricultural

practices and the discharge of urban and industrial

waste, particularly in Musoma, Jinja, and Kisumu.

This has affected the mobility of fisherfolk in

Lake Victoria region, significantly affecting their

means of earning a living. Fisherfolk’s movement

patterns, such as migration and commuting, play a

vital role in shaping their livelihood strategies

(Nunan and Cepić 2020). The urgency of address-

ing these issues has led to the involvement of

women in lake conservation efforts.

Additionally, the introduction of non-native

fish species such as Oreochromis (Linnaeus

1857), Oreochromis leucostictus (Trewavas,

1933), Tilapia zilli (Gervais, 1848), and Lates

niloticus Linnaeus, 1758, during the early 1960s

resulted in interspecific competition and preda-

tion, leading to a decline in native fish species.

According to Getabu et al. (2003), there was a

continual decrease in Nile perch biomass along

Lake Victoria shorelines, while populations of

small pelagic species exhibited growth. Authors

underscored the importance of establishing

straightforward guidelines for species identifica-

tion and implementing hydrographic monitoring

to enhance the accuracy of echo-trace classifica-

tion. Given the absence of any other comprehen-

210 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

mover prácticas de pesca sostenibles, salvaguardar hábitats críticos y reintroducir especies de peces nativas. Además, se está explo-

rando la cría de peces en jaulas como una posible solución para aliviar la presión sobre las poblaciones silvestres, como sugieren varios

autores. Las recomendaciones que surgen de este estudio incluyen realizar análisis de poblaciones virtuales para evaluar el stock de

especies autóctonas, intensificar los esfuerzos de conservación, diversificar las prácticas de pesca, ampliar la piscicultura en jaulas,

aumentar la conciencia y la educación públicas y mejorar los marcos de políticas y gobernanza. Al implementar estas recomendacio-

nes, existe optimismo sobre la recuperación y la resiliencia de las especies de peces autóctonas en el Lago Victoria, lo que conducirá

a la conservación de la biodiversidad y la promoción de medios de vida sostenibles para las comunidades locales.

Palabras clave: Perca del Nilo, extinción, especies invasoras, cíclidos africanos, introducción de especies exóticas.

sive source for estimating biomass, this study

highlighted the significant utility of acoustic sur-

veying as a valuable tool for assessing biomass in

Lake Victoria. This has raised concerns among

fisheries management experts regarding the con-

servation and management of the remaining

endangered fish species. The combination of

these introduced alien species with factors such

as population growth, the use of illegal fishing

methods and gears, the destruction of breeding

and nursery grounds for native fish species, the

illegal, unreported and unregulated (IUU) fishing,

and changes in environmental conditions have

significantly altered the composition of fish pop-

ulations in Lake Victoria, resulting in a decline in

species biodiversity (Witte et al. 2013). This

study also explored how cichlid species diversity

varies between naturally turbid and anthropogeni-

cally turbid habitats in Lake Victoria, shedding

light on factors influencing the distribution and

abundance of these unique fish species.

Currently, endemic fish species in Lake Victo-

ria are rarely observed, with some facing the risk

of complete disappearance and extinction (van

der Meer et al. 1995; Njiru et al. 2008a). Howev-

er, these vanished species from Lake Victoria can

now be found in neighboring satellite lakes,

dams, associated wetlands, and major islands

within the lake basin (Kaufman 1992). This

author reported on the catastrophic decline in bio-

diversity within Lake Victoria with the introduc-

tion of non-native species, particularly the Nile

perch, which led to the extinction of many indige-

nous fish species. This decline in biodiversity had

far-reaching ecological consequences. Further-

more, the study also highlighted how the intro-

duction of the Nile perch disrupted the existing

food web in the lake. Nile perch, being a top pred-

ator, led to a decline in smaller fish species such

as Happlochromis spp. and caused significant

changes in the trophic structure of the ecosystem

of Lake Victoria.

Notably, some species have been reported to

decline in prominent islands such as Kalangala

(Uganda), Migingo (Uganda/Kenya), and Rusin-

ga. According to Luomba et al. (2016), ecological

and economic impacts of IUU fishing in Lake

Victoria have contributed to overfishing, habitat

destruction, and reduced fish stocks, hence the

decline in most vital fish species. These islands,

and alternative water bodies including rivers such

as rivers Sio, Nzoia, and Nile, have distinct char-

acteristics, e.g. the absence of Nile perch,and are

often densely populated by emergent and sub-

emergent aquatic macrophytes that act as breeding

sites for most ingenious fish species. According to

van den Broek et al. (2020), these plant masses act

as significant barriers to fish reproduction and are

unsuitable for species intolerant to low oxygen

levels and high turbidity. Therefore, given the sig-

nificant decline in fish biodiversity and the immi-

nent threat of extinction for both native and intro-

duced fish species in Lake Victoria, it has become

crucial to identify and locate these endangered

species in other water bodies within the lake basin

and wetland areas of Lake Victoria.

Similarly, Odhone et al. (2020), in their study

on gender roles in the dagaa (Rastrineobola

argentea) fisheries value chain, observed a

notable decline in crucial fish species, including

dagaa, which used to be abundant and had a sig-

nificant impact in the livelihood of local commu-

nities. Niyonkuru et al. (2023) reported a similar

finding in their study on population dynamics and

exploitation levels of two clupeid fish species,

Stolothrissa tanganicae and Limnothrissa

miodon, in the Burundian waters located in the

northeastern region of Lake Tanganyika. Cinner

et al. (2015) also reported on the changing adap-

tive capacity of fishing communities along

Kenyan Lake Victoria, resulting in a decline of

fish species and caused fishing communities to

venture into cage farming along Lake Victoria

shorelines. This is evidenced by the mass fish

death reported among cage fish farmers in Kenya.

Despite extensive research conducted within

the Lake Victoria ecosystem, ongoing ecological

changes persist, primarily driven by climate

211

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

change, cultural eutrophication resulting from

industrial activities, population pressure, and

agricultural practices along the lake shorelines

has also resulted in a decline in indigenous fish

species of Lake Victoria (Mothersill et al. 1980).

The introduction of predatory fish species, such

as L. niloticus, has also had detrimental effects on

native fish species (Njiru et al. 2018). The signif-

icant reduction in fish species has resulted in

alterations of trophic levels and overall flora and

fauna patterns within the lake ecosystems.

According to Witte et al. (2013), these impacts

have not only led to the loss of fish species bio-

diversity but have also affected the water quality

of the lake, primarily due to high algae bloom

leading to eutrophication. Overfishing and the

proliferation of water hyacinths further disrupt

the breeding sites of endangered species, espe-

cially in Kenya (Obiero et al. 2015). Authors fur-

ther found that the impact of co-management

strategies on the sustainability of fish stocks has

led to improvements in fisheries resource conser-

vation in Lake Victoria, or that overfishing

remains a concern. Similarly, research on species

distinction and the biodiversity crisis in Lake

Victoria revealed that approximately 80% of

native fish species in Lake Victoria are either

endangered, extinct or at risk of extinction due to

various human activities taking place along the

east African shorelines of Lake Victoria (Witte et

al. 2007a).

This paper aimed to provide a comprehensive

review of observed alterations in the fish fauna of

Lake Victoria and investigated the potential caus-

es behind these changes. The primary objective

was to advocate for the conservation of the lost

biodiversity of Lake Victoria by identifying and

establishing diversity and sanctuary sites where

species are believed to thrive. To facilitate this

analysis, the study divided the lake’s history and

fish species biodiversity over the last century into

three distinct decade periods: before the introduc-

tion of Nile perch in the early 1980s, during the

Nile perch introduction period, and the current

scenarios. By examining these periods, a compre-

hensive understanding of changes in the fish

fauna of Lake Victoria can be gained, enabling

the implementation of effective conservation

efforts.

The information in this review article was

compiled from various secondary sources,

including international journals, conference pro-

ceedings, internet searches, and relevant materi-

als. The article covers the period from 1950 to

2023, incorporating 143 peer-reviewed articles

focused on the evolution of fish species and the

current state of biodiversity in Lake Victoria.

Additionally, literature data related to fisheries

management in Kenya, Uganda, and Tanzania

was explored. Careful attention was given to

organizing the secondary source materials in a

logical sequence concerning Lake Victoria’s fish-

eries and fish fauna biodiversity.

Study area

The Lake Victoria basin refers to the region

surrounding Lake Victoria, the largest freshwater

lake in Africa and the second-largest in the world

(Figure 1). It spans Kenya, Tanzania, and Uganda

and covers an area of approximately 250,000 km2

(Verschuren et al. 2002). The basin is known for

its rich fish biodiversity and ecological impor-

tance. While some fish species are underreported

due to overfishing and predation, notable species

in Tanzania include tilapia and Nile perch, vital

for both commercial and subsistence fishing

(Onyango 2011). The basin also supports diverse

bird species and mammals like hippos and croco-

diles (Ikingura et al. 2006).

In Kenya, the Lake Victoria basin comprises

eight significant rivers, namely Sio, Nzoia, Yala,

Nyando, Sondu, Miriu, Migori, and Mara. These

rivers, located west of the Rift Valley, contribute

nearly half of Kenya’s runoff, flowing into Lake

Victoria acting as a breeding ground for most of

indigenous fish species such as lungfish (P.

aethiopicus) (Njiru et al. 2008a). The basin is the

212 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

largest and most critical of the five catchments

that feed Lake Victoria, playing a vital role in

supporting downstream countries such as Sudan

and Egypt through the River Nile (Ntiba et al.

2001; Aura et al. 2020). In Kenya, the basin

encompasses Nyanza and western Provinces,

extending from Cherangani Hills to Mau Forest

and including the former Rift Valley Province and

Masai Mara Game Reserve (Kundu et al. 2017).

However, with the extensive basin, conservation

of indigenous fish species is still an issue due to

overfishing and predation associated with L.

niloticus.

The Lake Victoria basin holds immense impor-

tance for east Africa due to its abundant

resources, including fisheries, biodiversity, water,

land, forests, wildlife, minerals, transportation

routes, communication networks, and tourism

potential (Hecky 1993). It offers opportunities for

environmental conservation, preservation of

indigenous fish species, scientific research, socio-

political collaboration, and economic investments

(Muyodi et al. 2010). Recognizing its signifi-

cance, the East African Community (EAC) desig-

nated the basin as an ‘economic growth zone’

(Ogutu-Ohwayo 2004).

Rivers within the Kenyan catchment area of

the Lake Victoria basin contribute to the world’s

largest freshwater fish species. This fishery has

an average value of 980,000 t and generates an

estimated annual revenue of over USD 560 mil-

lion (Allison and Ellis 2001). Various conserva-

tion projects, such as the Lake Victoria Environ-

mental Management Project (LAVEMP), have

213

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

Figure 1. Lake Victoria basin with potential fisheries resources sites and the three riparian countries.

UGANDA

KENYA

TANZANIA

been initiated through the Lake Victoria Fisheries

Organization to protect and sustain the economic

benefits of Lake Victoria and environmental con-

servation (Witte et al. 2000; Langan et al. 2018).

Despite the implementation of various fish-

eries management and Lake Victoria manage-

ment initiatives by the three riparian countries,

i.e. Kenya, Uganda and Tanzania, the native fish

population in the lake has been steadily declining.

According to Cadwalladr (1965) and Gouds-

waard et al. (2002a), many of the original fish

species, such as lungfish (P. aethiopicus), that

once inhabited the lake basin, have disappeared.

Therefore, the conservation of remaining species

has become a pressing concern for fisheries

researchers at both local and international level.

However, finding a solution is complicated by

numerous governance and fisheries management

challenges in the fisheries sector across the three

riparian countries sharing fishery resources in

Lake Victoria.

Exploring the pre-Nile perch era: a historical

overview of Lake Victoria and its early fish

species biodiversity

Lake Victoria is renowned for its diverse fish

fauna, particularly the cichlid fish species. During

the pre-Nile perch era, the lake homed a rich vari-

ety of unique and endemic fish species (Kaufman

et al. 1997). Among these, Haplochromis sp.

(cichlids) was the most abundant and diverse

group (Ogutu-Ohwayo 1990a) (Figure 2), dis-

playing a wide range of colours, shapes, and

behaviours (Kaufman et al. 1997). The lake was

characterized by the remarkable adaptive radia-

tion of several endemic haplochromine cichlid

species (Eggert and Lokina 2010), that played a

significant role in the ecological dynamics of

Lake Victoria (Vranken et al. 2019). Throughout

history, their presence and abundance in Lake

Victoria have been influenced by various factors

(Meer 1993). In the past, Lake Victoria harboured

214 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

Figure 2. Percentage of indeginous fish species landed in Lake Victoria in 1957. Data redrawn from (Ogutu-Ohwayo 1990b).

Uganda

Kenya Tanzania

otal capture %T()

Oreochromis esculentus

Labeo victorianus

Haplochromine spp.

Oreochromis variabilis

Prot pterus aethiopicuse

Rasteneobola angentenea

Other species

Synodontis spp.

Brycinus jcksonii

Schilbe intermedious

Clarias gariepinus

Barbus altienialis radcliﬃ

Bagrus docmak

Mormyrus kanume

a large number of endemic haplochromine cichlid

species, with estimates ranging from 500 to 800

species (Njiru et al. 2005; Vranken et al. 2019).

These cichlids constituted a dominant group in

the fish community and played crucial roles in its

ecosystem, including trophic interactions, nutri-

ent cycling, and habitat structuring. However, the

introduction of non-native species, overfishing,

habitat degradation, and pollution have severely

affected the cichlid populations in Lake Victoria,

as reported by Kaufman et al. (1997) and Njiru et

al. (2014).

The most significant ecological disturbance

occurred in the 1980s when the predatory Nile

perch (L. niloticus) was introduced into the lake to

revive declining fisheries (Kaufman et al. 1997;

Zeeuw 2010). The Nile perch decimated numer-

ous haplochromine cichlid populations, especially

those in the nearshore areas of Kenya and Uganda,

where the Nile perch was most abundant (Njiru et

al. 2008b). It was estimated that over 200 hap-

lochromine cichlid species went extinct because

of this introduction (Witte et al. 1992; van der

Meer et al. 1995; Ogutu-Ohwayo 2004). The

decline of haplochromine cichlids caused a cas-

cade of ecological changes in Lake Victoria. With

the disappearance of cichlids, the balance of the

fish community was disrupted, leading to an

increase in algal blooms and a decline in water

quality (Konijnendijk et al. 2011). Additionally,

the loss of cichlids significantly impacted the

livelihoods of local fishing communities, who

relied on them for their sustenance and income.

This primary threat was likely to be overfishing,

leading to declines in fish populations, especially

for commercially valuable species along the Yala

River basin in Lake Victoria (Aloo 2003).

In recent years, efforts have been made to

restore cichlid populations in Lake Victoria. Con-

servation programs have focused on protecting

and restoring critical habitats, implementing fish-

ing regulations and controlling the spread of inva-

sive species (Achieng 1990). As a result, there

have been some positive signs of recovery for

haplochromine cichlids in certain areas of the

lake in Kenya, Uganda, and Tanzania. However,

according to Naigaga et al. (2011), the recovery

process is complex and ongoing, as the resilience

of haplochromine cichlids is still threatened by

multiple factors, including continued fishing

pressure, habitat degradation, pollution, and cli-

mate change. Additionally, Witte et al. (2007a)

observed that the introduction and spread of new

invasive species pose ongoing challenges for the

restoration of cichlid populations in Lake Victo-

ria. The history of haplochromis cichlids in Lake

Victoria has been characterized by their ecologi-

cal dominance, followed by a severe decline due

to human activities. While efforts have been

made to restore their populations through the

adoption of fisheries regulations, especially in

Kenya (Aura et al. 2020), the overall trend

remains precarious, requiring sustained conserva-

tion efforts to ensure the long-term survival of

these iconic fish in Lake Victoria.

Regarding O. esculentus (ngege/tilapia), it is

important to note that this species is no longer

commonly found in Lake Victoria. It has been

reported as extinct in the lake. Currently, there are

several known tilapia species in Lake Victoria,

including O. niloticus and O. leucostictus. The

trend in capture for tilapia in Kenya, Uganda, and

Tanzania has been on the decline (Njiru et al.

2005). These authors further suggested effective

management options that included regulations,

restoration efforts, balanced harvesting, commu-

nity involvement, research, and international

cooperation to ensure the sustainability of the

fishery while mitigating the ecological impacts of

exotic species.

The African lungfish (P. aethiopicus) is a prim-

itive fish species that can tolerate drought condi-

tions and inhabits swamps and stagnant areas of

Lake Victoria (Goudswaard et al. 2002a). This

species has a long evolutionary history and is

considered a living fossil. Before the introduction

of the Nile perch in Lake Victoria, the African

catfish was the dominant species, and the pres-

215

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

ence of African lungfish in the lake can be traced

back to prehistoric times when it was part of a

larger water system known as Lake Victoria-Nile

(Fryer 1960). The current status of the African

lungfish is uncertain, and its conservation is a

concern due to various factors affecting the lake

ecosystem. Environmental changes caused by

human activities such as deforestation, pollution,

and the introduction of invasive species can

impact P. aethiopicus population (Sitoki et al.

2010). Additionally, the African lungfish has been

subjected to intensive fishing pressure, both for

subsistence and commercial purposes (Ver-

schuren et al. 2002; Onyango and Jentoft 2010).

The silver cyprinid (R. argentea), also known

as omena or dagaa, is a small pelagic fish that

plays a significant role in the Lake Victoria food

web. It is an essential source of protein for local

communities and is crucial to the lake ecosystem.

Dagaa is one of the early fish species found in

Lake Victoria prior to the introduction of the Nile

perch (Odhone et al. 2020). However, it is impor-

tant to note that the lake ecosystem and fish pop-

ulation have undergone significant changes over

time due to various factors, including human

activities and the introduction of non-native

species (Fryer 1960; Witte et al. 2007b).

Indigenous cyprinids

Lake Victoria was historically known for host-

ing a diverse array of cyprinid fish species (Cad-

walladr 1965). However, in recent years, some of

these species, including L. victorianus, known

locally as ‘ningu’ in Kenya and Tanzania, have

become endangered and have disappeared from

fishermen’s nets (Figure 3). Labeo victorianus

was once abundant in local markets along the

shoreline of Lake Victoria and its surrounding

areas, with a high number of individuals being

caught in Kenya and Tanzania (Cadwalladr

1965). The decline in the capture of L. victorianus

can be attributed to several factors, including the

introduction of the Nile perch in the lake (Moth-

ersill et al. 1980). Since then, the population of L.

victorianus has suffered significantly, as the Nile

perch is believed to prey on L. victorianus (Cad-

walladr 1965; Hauser et al. 1998; Njiru et al.

2005). Additionally, overfishing and the use of

illegal fishing gear, such as beach seines and fish

poisoning (Eggert and Lokina 2010), have con-

tributed to the decline of L. victorianus in Kenyan

waters. Unfortunately, the current status of this

species is largely unknown to both fisheries

experts and local fishermen. Conducting stock

assessments will therefore play a vital role in

informing conservation efforts and ensuring the

long-term survival of L. victorianus in Lake Vic-

toria (Witte et al. 2007a, 2007b). The decline of

L. victorianus and other cyprinid fish species in

Lake Victoria is a concerning issue. It is essential

to address factors contributing to their decline,

such as the introduction of invasive species

(Fryer 1960), overfishing (Nunan 2014), and the

use of illegal fishing methods (Njiru et al. 2014).

Therefore, according to Mkumbo and Marshall

(2015), signs of overfishing in the Nile perch

population of Lake Victoria are a cause for con-

cern due to their ecological, economic, and social

implications. Effective management measures,

including fishing regulations, gear restrictions,

and community involvement are essential to

address these challenges and ensure the long-term

sustainability of the Nile perch fishery and the

health of the lake’s ecosystem.

Barbus altinialis is another cyprinid species

once thrived in Lake Victoria until the introduc-

tion of L. niloticus. It was predominantly cap-

tured along the Migori and Mara rivers. Before

the 1980s, B. altinialis made a substantial contri-

bution to fish landings, estimated to be over

8,700 t (Olowo and Chapman 1996). However,

over time, the population of B. altinialis has

declined significantly and current numbers are

not accurately reported (Kundu et al. 2017). The

whereabouts of these fish species raises ques-

tions. Witte et al. (2000) have revealed traces of

B. altinialis upstream in Kenyan rivers such as

Nzoia, Mara, Migori, and Sio, which drain into

216 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

Lake Victoria. This suggests that these rivers

could serve as an escape route for the species,

enabling them to evade the invasive L. niloticus

within Lake Victoria. Unfortunately, many

cyprinid species have experienced a significant

decline without adequate conservation measures

in place (Geheb et al. 2008).

The alarming rate at which indigenous fish

species are vanishing from Lake Victoria has

become a regional concern among the three ripar-

ian countries (Witte et al. 2013). The loss of these

species not only affects the ecological balance of

the lake but also has significant socio-economic

implications for local communities that depend

on fishing. Therefore, it is crucial for stakehold-

ers to recognize the importance of conserving

remaining populations of indigenous fish species.

The introduction of cage farming in Lake Victoria

can be a promising trial approach for the conser-

vation of such species. According to Njiru et al.

(2019), cage fish farming is currently considered

both a boom and a potential disaster. However,

when such endangered species are adopted and

fed formulated feeds with improved additives,

their growth and spawning rates can be enhanced

(Syanya et al. 2023a). Efforts should be made to

implement effective conservation measures,

including habitat protection, sustainable fishing

practices, and the control of invasive species

(Dudgeon et al. 2006; Okafor-Yarwood et al.

2020). Based on the findings of these authors,

cooperation between countries bordering Lake

Victoria, in addition to engaging local communi-

ties, researchers, and fisheries specialists, is

imperative to tackle this regional issue. By giving

precedence to the preservation of native fish

species, we can work towards rejuvenating the

ecological well-being of Lake Victoria and secur-

ing the enduring viability of its fish populations.

Family Mormyridae, commonly known as ele-

phant fish or mormyrids (Barilwa 1995), includes

a diverse group of freshwater species found in

various water bodies in Africa, including Lake

Victoria (Barilwa 1995; Gichuki et al. 2001) (Fig-

ure 4). These fish are known for their unique

physiological adaptations and specialized electric

sensing organs used for navigation, communica-

tion, and locating prey (Greenwood 1966). These

species have evolved to occupy different ecolog-

ical niches within the lake, adapting to various

217

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

Figure 3. Labeo victorianus (ningu) of Lake Victoria (retrieved from Okeyo and Ojwang 2015).

habitats and feeding strategies (Ogutu-Ohwayo

1990a). One well-known species of mormyrid

found in Lake Victoria is the Nile elephant fish

(Gnathonemus petersii) (Witte and Van Densen

1995). It is a large, torpedo-shaped fish with a

long snout and a unique electric organ (Green-

wood 1966; Chapman et al. 1996). This organ

generates weak electric fields that the fish use to

navigate and communicate in murky waters of the

lake. The Nile elephant fish primarily feeds on

small invertebrates and plant matter (Ligtvoet et

al. 1995). Similar fish species have been reported

during fish stock assessments in Lake Kyoga,

Uganda (Kudhongania et al. 1992).

Before the introduction of Nile perch and the

impact of climate change within the East African

region, a total of five species from Family

Mormyridae were observed (Seehausen 1996;

Witte et al. 2000). Among them, four small

mormyrid species, specifically Pollimyrus nigri-

cans,Hippopotamyrus grahami,Marcusenius

victoriae, and Gnathonemus longibarbis (Outa et

al. 2020), were found exclusively near mouths of

rivers Awach (Kendu Bay) and Sio. The fifth

species, Mormyrus kannume, a larger species

218 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

highly sought after commercially, was observed in

rocky areas around Asembo Bay, Mbita, and at the

mouth of Nzoia River, Kenya (Cadwalladr, 1965;

Seehausen 1996; Katunzi 2000). All of these river

mouths have soft bottoms and shallow waters,

with adjacent papyrus swamps, similar to those

reported in Lake Naivasha, Kenya (Muthuri

1989). However, since the introduction of Nile

perch fishing communities along Lake Victoria

have reported the disappearance of all of these

species. For instance, Ogutu-Ohwayo (1995)

observed that small species were captured in nets

that were set overnight, while no mormyrids were

caught in nets set during daytime. These findings

support the observations made by Welcomme

(1964) that certain fish species exhibit habitat and

habit preferences, with migrations typically

occurring at night, particularly during dusk and

dawn. This explains why the majority of fisher-

men in Lake Victoria prefer to fish at night.

According to Pitcher and Hart (1995), another

notable species in east African Lake Victoria is the

longfin mormyrid (Pollimyrus isidori). This

species possesses elongated fins and a slender

body, enabling it to navigate efficiently through

Figure 4. Mormyrus kannume of Lake Victoria (retrieved with permission from https://www.hippocampus-bildarchiv.de/tier_37

18_Mormyruskannume.htm).

the dense vegetation and shallow waters of the

lake. It utilizes its electric organ to detect prey

and communicate with conspecifics (Pitcher and

Hart 1995; Rabuor and Polovina 1995). The east

African longfin mormyrid primarily feeds on

small aquatic insects and crustaceans (Bugenyi

1998).

In addition to overfishing and the impact of

invasive Nile perch on indigenous fish species, it

is important to note that the ecosystem of Lake

Victoria has undergone significant changes in

recent decades (Kudhongania et al. 1996; Njiru et

al. 2000). These changes include but are not lim-

ited to, the invasion of water hyacinth (Harley

1990; Njiru et al. 2000; Van der Knaap et al.

2002), the introduction of non-native fish species

(Taabu-Munyaho et al. 2016; Ogari 2000), and

environmental degradation (Hecky and Bungenyi

1992; Harper and Mavuti 1996). These factors

have impacted mormyrid populations and their

habitats, emphasizing the importance of conser-

vation efforts for their long-term survival. They

have significantly contributed to the decline in

mormyrid fish species within Lake Victoria.

Synodontis victorianus

Synodontis is a genus of catfish that is widely

distributed throughout major lakes of Africa,

including Lake Victoria. Within Lake Victoria,

several species of Synodontis can be found, each

with its own specific distribution patterns and

ecological preferences (Mothersill et al. 1980;

Aloo 2003). According to Witte et al. (2007a), S.

victorianus is endemic to Lake Victoria and is one

of the most common and abundant catfish-like

fish species found in the lake. It is distributed

throughout the lake and can be found in various

habitats, including rocky shores, sandy bottoms,

and vegetated areas. Seehausen (1997) also

reported the existence of S. nigrita, a species

native to Lake Victoria with a wide distribution

across the lake. It is often found in rocky habitats,

especially along shorelines and near islands such

as Rusinga, Migingo, Kalangala and among

numerous other small islands in Lake Victoria

(Cadwalladr 1965; Ogutu-Ohwayo 1995).

Other species of Synodontis native to Lake Vic-

toria that have been reported include S. woosna-

mi,S. afrofischeri, and S. koensis (Witte et al.

2000; Njiru et al. 2005). Most of these species

prefer habitats with dense aquatic vegetation,

such as marshes, swamps, and areas with abun-

dant plant cover (Kashindye et al. 2015). There-

fore, before the introduction of Nile perch, the

distribution of Synodontis spp. within Lake Victo-

ria was influenced by various factors, including

habitat preferences, water quality, food availabili-

ty, and interactions with other fish species (Hecky

1993). Different species may occupy specific

niches within the lake (Witte et al. 2013), utilizing

different feeding strategies and occupying differ-

ent microhabitats. It is worth noting that the intro-

duction of non-native fish species, such as the

Nile perch, has had significant impacts on the

native fish populations in Lake Victoria, including

Synodontis species, affecting the distribution and

abundance of many native fish species (Green-

wood 1974; Pitcher and Bundy 1995). According

to several authors, such as Witte et al. (2007b),

Hecky et al. (2010) and Taabu-Munyaho et al.

(2016) Synodontis has become one of the endan-

gered fish species in Lake Victoria, with a decline

in catches among the three riparian countries.

The dominance Nile perch era and the decline

in fish species diversity in Lake Victoria

Lake Victoria has undergone significant

changes in the biodiversity of its fish species and

ecosystem dynamics since the introduction of the

Nile perch in the 1980s. According to Achieng

(1990), who assessed the impact of the Nile perch

introduction in Lake Victoria, this species is a

predatory fish that was introduced with the inten-

tion of boosting fisheries and controlling the pop-

ulation of smaller fish species, particularly intro-

duced predatory cichlids. However, Taabu-Mun-

yaho et al. (2016) reported that the unintended

219

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

consequences of the Nile perch introduction have

been profound.

Prior to the introduction of the Nile perch,

Lake Victoria was known for its diverse and

unique fish fauna, comprising numerous endemic

fish species (Fryer 1960). The lake was home to

hundreds of different cichlid species (Kudhonga-

nia et al. 1992), along with other fish families

such as catfish (Synodontis spp.), lungfish (P.

aethiopicus), and tilapia (Oreochromis spp.)

(Ogutu-Ohwayo 1990a; Goudswaard et al.

2002b).

Immediately after the introduction of Nile

perch, it became the dominant predator in Lake

Victoria, leading to a decline in the diversity and

abundance of endemic cichlid species. Many

endemic cichlid populations were decimated or

entirely wiped out, causing a loss of biodiversity

and ecological disruption (Mkumbo and Ligtvoet

1992; Matsuishi et al. 2006). Ogutu-Ohwayo

(1990b) estimated that more than 200 cichlid

species have become extinct or severely endan-

gered due to the presence of Nile perch.

Despite the ecological impacts of the introduc-

tion of Nile perch, the Nile perch fishery expand-

ed rapidly due to its economic value as an export

commodity (Matsuishi et al. 2006). The fishing

industry targeting Nile perch became a significant

sector in the eastern Africa region, with large-

scale commercial fishing and processing opera-

tions (Natseba et al. 2005; Matsuishi et al. 2006).

However, overfishing and unsustainable practices

have posed additional challenges to the long-term

viability of the fishery (Reynolds et al. 1995). Fish

processing factories have been set up to handle the

increased Nile perch capture, ensuring the quality

of fish through freezing and frozen storage

(Karungi et al. 2004; Syanya et al. 2023b). This

has increased due to the exploitation of not only L.

niloticus but also other indigenous tilapia species.

Njiru et al. (2005) reported that the expansion

of the Nile perch fishery in Lake Victoria has fol-

lowed a notable trend over the years. Indigenous

fish species are on the brink of decline due to the

highly predatory nature of the Nile perch colony

in the lake. According to Nunan (2010), the fish-

ery initially experienced a rapid increase in fishing

efforts and commercial operations following the

introduction of the Nile perch in the 1980s. The

high demand for Nile perch in international mar-

kets, particularly in Europe and the United States

of America, fueled the expansion of the fishery

(Kudhongania et al. 1992; Hauser et al. 1998).

Therefore, very little concern was given to indige-

nous fish species of Lake Victoria, which are

believed to fetch a lower price in the global fish

market. Who cares? Fisheries conservation meas-

ures set in place within fisheries management

policies and acts of the three riparian countries are

silent on the conservation of biodiversity of fish

species of Lake Victoria (Witte et al. 2013).

During the 1970s and 1980s, the fishery of

Lake Victoria reached its peak with a surge in fish-

ing fleets and processing facilities around the lake

(Ntiba et al. 2001). The introduction of more effi-

cient fishing techniques and larger vessels con-

tributed to increased catch rates and higher pro-

duction levels. This period witnessed a substantial

rise in export volumes of Nile perch (Witte and

Van Densen 1995; Ntiba et al. 2001; Eggert and

Lokina 2010), making it a significant economic

activity for countries surrounding Lake Victoria.

However, as the fishery expanded, concerns about

sustainability and impacts on the lake ecosystem

began to emerge. Overfishing became a prominent

issue, with some areas experiencing a decline in

Nile perch populations and the depletion of small-

er fish species, including the endemic cichlids

(Seehausen 1996; Cowx et al. 2003). In response

to these concerns, efforts were made to regulate

the fishery and implement sustainable practices.

Fishing quotas and size and species restrictions

were introduced to protect juvenile fish and allow

for stock recovery (Eggert and Lokina 2010). Col-

laborative initiatives involving government

authorities, fishing communities, and conservation

organizations were also established to promote

responsible fishing practices and ensure the long-

220 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

term viability of the Nile perch fishery (Ntiba et

al. 2001; Obiero et al. 2015). However, very little

has been done to control the direct impact of

predatory effects of Nile perch on declining native

fish species, as evident from landing data reports.

This has resulted in the mobility of fishermen

seeking better livelihoods (Nunan 2010).

In recent years, the expansion of the Nile perch

fishery has become more focused on sustainable

practices and responsible management. This

included promoting value-added processing,

quality control, and traceability systems to meet

international market standards and improve the

economic returns for fishers and processors

(Mkumbo and Marshall 2015). Additionally,

there has been a growing emphasis on addressing

social and environmental issues, such as labor

rights, bycatch reduction, and the reduction of

post-harvest losses (Njiru et al. 2005).

The introduction of Nile perch has brought

about a change in the composition of fish species

in Lake Victoria. For example, Greenwood

(1965), Fitzsimmons and Watanabe (2010), and

van der Meer et al. (2012) have documented a

decrease in native cichlids and the rise of Nile

perch as the dominant species, resulting in a sig-

nificant alteration of the fish species composition

of the lake. Currently, the most abundant and eco-

nomically significant fish in the lake is the Nile

perch and several introduced tilapia species, with

Nile tilapia (O. niloticus) being the primary one

(Kishe-Machumu et al. 2008; Seehausen 2008).

Many of endemic cichlids that once character-

ized the lake diversity have become rare or

extinct (Witte et al. 1992). Similarly, changes in

the fish species composition of Lake Victoria

have had far-reaching ecological consequences.

According to Seehausen (1998), the loss of

diverse cichlid species has affected the trophic

structure of the lake, nutrient cycling, and overall

ecosystem functioning. Furthermore, Witte et al.

(2000) documented that as a primary predator, the

Nile perch has disrupted the dynamics of other

cichlid fish populations in Lake Victoria and dis-

turbed the ecological equilibrium of the lake.

Therefore, recognizing ecological challenges and

the importance of preserving the biodiversity of

Lake Victoria, conservation efforts have been ini-

tiated. Efforts included measures to protect

remaining endemic cichlid species and the estab-

lishment of closed seasons during critical fish

breeding periods to protect spawning aggrega-

tions and ensure the recruitment of young fish

into the population (Greenwood 1974), restore

degraded habitats such as swamps and lakes

along noticeable rivers such as Sio and Yala

(Aloo 2003), promote sustainable fishing prac-

tices, and regulate the fishing industry to ensure

the long-term sustainability of the lake’s

resources (Okeyo 2014). The decline of endemic

cichlids and the dominance of the Nile perch have

reshaped the ecosystem dynamics and posed

challenges for conservation and sustainable fish-

eries management. However, according to Muyo-

di et al. (2010), efforts were initiated in order to

mitigate impacts and restore the ecological bal-

ance of fish communities of Lake Victoria.

Conservation measures to protect indigenous

fish species from Nile perch predation in Lake

Victoria

Conservation measures aimed at protecting

indigenous fish species from Nile perch predation

in Lake Victoria involve a combination of strate-

gies to preserve and restore the ecological bal-

ance of the lake. Gichuki (1994) and Kokwaro

and Johns (1998) proposed habitat restoration

along the shorelines of Lake Victoria to preserve

and conserve indigenous wetland vegetation and

protect breeding grounds for most fish species.

Ogutu-Ohwayo (1990b) made a similar observa-

tion, emphasizing the importance of enhancing

and restoring critical habitats for indigenous fish

species. This author recommended promoting the

growth of aquatic vegetation, creating spawning

grounds, and protecting areas with high biodiver-

sity. These efforts provide shelter and food

221

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

sources for smaller fish species such as cyprinids,

reducing their vulnerability to Nile perch preda-

tion. Garrod (1961) reported that establishing

protected areas and fish sanctuaries can con-

tribute to the rational exploitation of Tilapia spp.

in Buruma islands of Lake Victoria. Protected

zones limit fishing pressure and provide a safe

refuge for vulnerable species such as Barbus spp.,

Mamyrus karnume, and Cynodontis spp. This

allows them to reproduce and maintain sustain-

able populations (Willoughby et al. 1993;

Reynolds et al. 1995).

Kaufman (1997) and Njiru et al. (2010) both

emphasized the importance of regulating fishing

practices as a measure to conserve the ever-

declining original fish species of Lake Victoria.

Implementing fishing regulations, such as mesh

size restrictions, closed seasons, and fishing quo-

tas, can contribute to the protection of indigenous

fish species (Njiru et al. 2008b; Outa et al. 2020).

By managing fishing efforts and preventing over-

fishing, these measures allow fish populations to

recover and reduce the pressure of Nile perch pre-

dation. Species-specific conservation programs

have also been initiated in different sections of

Lake Victoria to protect species such as the

African lungfish (P. aethiopicus) (Goudswaard et

al. 2002a). Developing targeted conservation pro-

grams focusing on endangered or threatened

indigenous fish species is crucial. These pro-

grams may involve captive breeding and restock-

ing efforts, genetic studies, and monitoring popu-

lation dynamics to ensure the survival and recov-

ery of these species within Lake Victoria basin

(Bailey and Jentoft 1990; Béné 2003; Mugisha et

al. 2007).

Invasive species management is another rec-

ommended approach (Achieng 1990; Ogutu-

Ohwayo 2004; Agembe et al. 2019). Based on the

findings of these authors, managing invasive

species, such as the Nile perch itself, is essential

to reduce its impact on indigenous fish popula-

tions. This can include measures like controlling

the introduction and spread of non-native species,

monitoring and mitigating the ecological effects

of invasive, and researching methods to manage

their populations.

Community engagement and education

through the formation of beach management units

within all landing sites along the shores of Lake

Victoria have also been reported (Ntiba et al.

2001; Njiru et al. 2008a). Involving local commu-

nities in conservation efforts is key to long-term

success. Similar findings were documented by

Chapman et al. (2002), emphasizing the need to

regulate the pollution of wetlands and swamps

that may result in the hypoxia of fish in Lake Vic-

toria. Engaging with fishing communities, raising

awareness about the importance of protecting

indigenous fish species, and promoting sustain-

able fishing practices can help foster a sense of

stewardship and ensure community support for

conservation initiatives (Mathia and Fotedar

2012; Syanya and Mathia 2023). By observing

these measures, local communities along shore-

lines of Lake Victoria can enhance fish health and

biosecurity management systems, thus conserv-

ing endangered fish species.

Collaborative governance among the three

riparian countries in boosting conservation and

researching on indigenous fish species of Lake

Victoria has been reported by Obiero et al. (2015)

and Nunan and Cepić (2020). Collaborating with

governmental authorities, researchers, conserva-

tion organizations, and local communities is cru-

cial for the effective conservation of declining

fish species in Lake Victoria (Nunan et al. 2012;

Etiegni et al. 2017). Engaging in collaborative

governance models can help ensure that decisions

regarding fishing regulations, habitat manage-

ment and conservation strategies are based on sci-

entific knowledge and include perspectives and

expertise of relevant stakeholders, most of whom

are women in Lake Victoria fisheries (Nunan et

al. 2012; Nunan and Cepić 2020). Therefore, by

implementing these conservation measures and

maintaining a holistic approach to the manage-

ment of Lake Victoria, it is possible to mitigate

222 MARINE AND FISHERY SCIENCES 37 (1): 209-231 (2024)

the impact of Nile perch predation on indigenous

fish species and restore the ecological balance of

the lake ecosystem.

FINAL REMARKS

The introduction of Nile perch (L. niloticus) to

Lake Victoria in the 1980s has had profound and

complex effects on the indigenous fish species in

the lake. This invasive predator has led to the

decline and extinction of many native fish

species, particularly cichlids (Achieng 1990;

Taabu-Munyaho et al. 2016). This has resulted in

ecological imbalances within the lake, impacting

the overall functioning of the ecosystem and

causing economic challenges for local communi-

ties. To address these challenges and ensure the

future prospects of indigenous fish species in

Lake Victoria, various conservation efforts and

initiatives are being undertaken. These include

promoting sustainable fishing practices, protect-

ing critical habitats, reintroducing native fish

species, and exploring cage fish farming as an

alternative source of income and a means to

reduce pressure on wild populations. Research

and monitoring programs are also crucial for

understanding ecosystem dynamics and inform-

ing management strategies.

Based on findings from explored articles, the

following recommendations are made:

·Strengthen conservation efforts: riparian coun-

tries should continue and enhance conservation

initiatives aimed at protecting indigenous fish

species in Lake Victoria. This includes promot-

ing sustainable fishing practices, establishing

protected areas, and implementing effective

management strategies.

·Diversify fishing practices: encourage the

diversification of fishing practices to reduce

reliance on indigenous fish species along the

shoreline of Lake Victoria as the primary target

species by local fishermen. This can help alle-

viate pressure on indigenous fish populations

and promote their recovery.

·Expand cage fish farming: develop and regu-

late cage fish farming as a means to reduce

pressure on wild populations and provide alter-

native income sources for local communities.

However, it is crucial to prioritize the imple-

mentation of appropriate monitoring and man-

agement measures to prevent incidents such as

fish poisoning.

·Collaborative research and monitoring: the

three riparian countries should Foster collabo-

ration among research institutions, organiza-

tions, and local communities to conduct com-

prehensive research and monitoring programs.

This will improve understanding of the ecosys-

tem dynamics, evaluate the impacts of Nile

perch predation, and inform evidence-based

management decisions.

·Promote public awareness and education:

increase public awareness and education about

the importance of conserving indigenous fish

species and the ecological significance of Lake

Victoria. Promote sustainable fishing practices

and engage local communities in conservation

efforts through capacity building and outreach

programs.

·Strengthen policy and governance: enhance

policy frameworks governance structures and

fisheries legal instruments to ensure the effec-

tive implementation of conservation measures

and sustainable management practices. This

can include the establishment of regulations,

enforcement mechanisms, and collaboration

with regional and international organizations.

·Long-term monitoring and evaluation: estab-

lish long-term monitoring and evaluation pro-

grams to assess the effectiveness of conserva-

tion interventions and adapt strategies as need-

ed. Regular monitoring of fish populations,

habitat conditions, and socioeconomic factors

will provide valuable insights for adaptive

management.

223

SYANYA ET AL.: THE DECLINE IN THE ORIGINAL FISH FAUNA OF LAKE VICTORIA

By implementing these recommendations,
there is a higher likelihood of restoring and main-
taining the biodiversity and ecological balance of
Lake Victoria, while also supporting the sustain-
able livelihoods of local communities dependent
on fisheries resources. These efforts are essential
for securing the future of indigenous fish species
in the lake and preserving its ecological integrity.
Author contributions
Fredrick Juma Syanya: conceptualization, lit-
erature review, writing-original draft. Zachary O.
Winam: further review of the literature and edit-
ing. Wilson M. Mathia: drawing figures, visuali-
zation, formal editing and grammar checking.
Competing interests
All authors collectively and unanimously
declare that they have no competing interests in
this work and that no funding was obtained to
fund this research work.
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