Endangered and threatened fish species of Victoria: Status, options and way forward

Outa N. Otieno1*, Yongo E Omollo2 James Last A. Keyombe3, Namwaya David W.4

1Centre for Research and Technology Development (RESTECH), Maseno University, P.O.

Box 3105-40100, Kisumu, Email address: [email protected].

2University of Eldoret, Department of Fisheries and Aquatic Sciences, P. O Box 1125,

Eldoret, Kenya, Email: [email protected].

3Kenya Marine and Fisheries Research Institute, Research Station, P.O. Box

205 - 30500, Lodwar, Kenya Email: [email protected].

4Fisheries Department Turkana County Government, P.O Box 55 – 30500, Lodwar, Kenya

Email: [email protected]. Abstract

Lake Victoria, the second largest freshwater lake in the world supports a huge flora and fauna with a large human population around the Lake. The Lake is a source of food

(fish), water for domestic use and crop and livestock production, transportation, tourism among others. Due to its varied uses, human intervention within the lake and its catchment has caused several ecological changes in the recent years with profound effects on the resource resources. One of the most notable change is the reduction and risk of extinction of some fish species, including the endemic tilapiine species ( esculentus and O. variabilis), catfishes (Xenoclarias eupogon), and cyprinids ( victorianus and Barbus altinialis) within the lake. The reduction in biodiversity and extinctions within the lake has been ascribed to the introduction of alien fish species ( (Lates niloticus) and Nile tilapia (O. niloticus) into the lake, loss and the cultural eutrophication. These changes if left unchecked will have devastating effects on the lake’s resources and at large to people living around the lake and beyond who depend on the lake for their livelihood. There is therefore an urgent need for management measures based on sound scientific research to be taken in order to curb the loss of ichthyodiversity within the lake and to save livelihoods of the direct and indirect dependents of the lake.

Key words: Endangered, , diversity loss, haplochromines 1. INTRODUCTION

Lake Victoria is the world's second largest lake with an area of 68,800 km2, mean depth of 40 m shared among Kenya (6%), Uganda (43%) and Tanzania(51%). It supports one of the world's largest freshwater fisheries providing employment and food to millions around the lake and beyond (Sayer et al., 2018). The lake supports one of the world’s most productive inland Fisheries with a total catch of about a million tonnes with Tanzania contributing 66.6%, Uganda 18.6% and Kenya 14.8% (Turyaheebwa, 2014). The value of the catch at the beach level is estimated at more than USD 550 Million and an export value of

260 Million .The fish yield from the lake is estimated at 1 million tonnes per year (LVFO

2009). Some of the problems facing the lake are intensive non-selective fishing, catchment degradation, industrial and agricultural pollution, the introduction of exotic species (e.g. Nile perch and Nile tilapia) and uneven patchwork of governmental laws ( Ogello et al., 2013).

Ogello et al (2013) highlighted Hardin’s argument that freedom of the commoners has caused resource overuse in the lake leading to poverty and therefore recommend access limitation as a way of encouraging wise use of the lake’s resources.

Lake Victoria has attracted much interest in recent years with several research projects collecting data on several aspects of the lake from its fisheries to ecological aspects.

This is because fish is known to react to environmental degradation, overfishing, predation and competition and series of environmental changes (Balirwa et al., 2003). Some of the observed changes have been the decline or even disappearance of some fish species within the lake. This has profound effect on the fishery of the lake and livelihood of the people who depend on the lake. Several projects mainly funded by international non-governmental organizations have generated data which have been the basis to come up with better management strategies for the fisheries and other resources within the lake. In 1996, for example the World Bank funded the Lake Victoria Environmental Management Project (LVEMP) with the primary objective to restore and sustain the ecology of Lake Victoria and its fisheries. This research project was implemented in collaboration with the research institutions of Kenya, Uganda and Tanzania. The focus of these institutes is generation of new data on the status of the fisheries and other ecologically important information on the portion of the lake within the respective countries, and to formulate scientifically sound management strategies. Despite the numerous research projects, Lake Victoria has undergone several ecological changes due to the effects of cultural eutrophication mainly driven by population increase and industrialisation (Sitoki et al., 2010). Other problems include the impact of introduced species like the predatory Nile perch as well as over exploitation of the fishery which has led to reduction or/and even disappearance of some fish species within the lake. The severe reduction in fish species diversity has led to modification in the trophic patterns of the Lake Victoria ecosystem, including alterations in floral and faunal composition, and reduced grazing pressure on phytoplankton (Aloo, 2003). This has not only led to changes in the biodiversity within the lake but also to the water quality especially due to the reduction in the number of grazers leading to algal blooms.

There is need in the world today to feed the ever growing population especially in

Africa not only with the right quantity but also quality of food. This is true for East Africa that is characterized by severe malnutrition (Sunguya et al., 2006). . Fish is a cheap and healthy source of protein (Keriko et al., 2003). Lake Victoria supported diverse fisheries of

( and cyprinid species which is on decline and risk extinction due to over exploitation, use of wrong gears, introduction of alien fish species (Nile perch) eutrophication

(Sitoki et al., 2010), overfishing and water Hyacinth (Sayer et al., 2018). Eutrophication and siltation that hinders mate selection and feeding in fishes (Seehausen et al., 2003). About

8% of the Native fish species in Lake Victoria are endangered and faced with danger of extinction (Sayer et al., 2018) due to the various anthropogenic activities in the region This paper focusses on the endangered and threatened fish species within Lake

Victoria and the ecological changes that might have caused the decline and worst the extinction of the number of fish species in the lake. It also suggests possible actions that could be taken to reduce the biodiversity loss and curb or reduce further ecological changes within the lake.

Methods

The Cyprinids

Lake Victoria once supported an array of Cyprinid species some of which are endangered or have disappeared completely from the catches in the recent years. In particular, the severe reduction of Labeo victorianus (locally known as “Ningu”), the only labeoninee in Lake Victoria and its catchment has been observed. A general decline in the catch of L. victorianus, a potamodromous fish species with was recorded around 1979 (Table

2) which coincided with the replacement of weirs and barriers by beach seins and small mesh size nets set at the river mouths. This is hypothesised to have led to further decline in the population of this fish in the later years (Kibaara, 1981). The contribution of L. victorianus to the catches in 1960s recording 595 tonnes in 1968 and 467 tonnes in1969, respectively

(Kibaara, 1981) decreasing in late 1980s from 204 fish per hectare to < 1 1990s and later years (Balirwa et al, 2003). Despite the reduction, catches are recorded in some rivers like

Nyando, Mara and Yala (pers. obs.), the numbers have considerably reduced as well as the length at maturity. This could be a survival tactic in response to the overfishing pressure as has been documented for Nile tilapia in Lake Victoria Njiru et al., (2004).

The decline in the number of Labeo in Lake Victoria, Kenyan waters can be attributed to fishing practices such as use of fish traps at the river mouths during migration catching mature fish before spawning. This dispossesses the gravid fish of the chance to contribute to the next generation leading to decline in numbers (Rutaisire & Booth, 2004). L. victorianus is in the list of IUCN Red List of Threatened species (Maithya et al., 2003) therefore urgent need for more research on the biology, ecology and potential propagation in captivity and culture. This will not only reduce pressure on the wild fisheries but will also help boost their population in the wild through re-introduction of the hatchery bred fingerlings into the lake and rivers flowing into it. Attempts to breed Labeo in captivity in Kenya (Wairimu et al.,

2008; Maithya et al., 2003) and Uganda (Rutaisire & Booth, 2004) has been tried with significant success a possibility of saving the endangered species.

Barbus altinialis is another cyprinids whose numbers have considerably gone down in the catches around the lake . The species is also listed in the IUCN Red List of Threatened

Species. Though still caught in some rivers like Migori and Mara (pers. obs.), they are rarely seen in other rivers and commercial landings (personal communication by fishermen). The contribution of this fish to the fish landings around the lake has declined from 8173 tons in the 1980s to 152 tons in the late 1990s and early2000 (Balirwa et al, 2003). There could be a further decrease in the numbers as the fish hardly recorded in the catches these days. Recent studies in the basin reported the presence of the species in the mid and lower ridges of

Kenyan rivers flowing into the Lake (Mwangi et al., 2012).

Haplochromine Cichlids

The upsurge of the introduced Nile perch compounded with reduction in water quality especially due to eutrophication have impacted negatively on the number of species in Lake Victoria (Sayer et al., 2018). Most Haplochromine species reduced remarkably in number except for a few species like Haplochromis pyrrhocephalus that have undergone some morphological changes to overcome the pressure from Nile perch (Witte et al., 2008). Katunzi et al., (2003) observed that H. pyrrhocephalus changed feeding behaviour from predominantly fish to include shrimps and molluscs a tactic to reduce niche overlap with Nile perch. Although most haplochromine cichlids of Lake Victoria are known for rapid evolution with an estimation of over 500 endemic species having evolved over 100,000 -

400,000 years, eutrophication pushed most of them to near extinction (Awiti, 2011). It is estimated that out of over 500 haplochromine species within the lake before the introduction of Nile perch, nearly 200 are now extinct (Goudswaard et al., 2008). Simo et al., (2009) observed that resource competition could be the most probable mechanism of the impact of the introduced species other than predation. Nile perch was observed to fed mainly on haplochromine cichlids and it is reported that this led to rapid decline in the number of haplochromines in the lake (Kitchell et al.,1997). In the 1970s for example, the contribution of haplochromines to the catches of lake Victoria were 22,464 metric tonnes (28.8%) and

32,552 metric tonnes (40.6%) in 1975 and 1976, respectively (Witte and Oijen, 1990). The contribution decreased sharply to 128 tons in 1980s and further to 4 tons in 1990s and 3 tons in 2000 (Balirwa et al., 2003; Goudswaard and Witte, 1997).

Most haplochromines are trophic specialists with strict choice of diet maturing at a small size and low productive potential due to their small clutch sizes. They also have extended parental care which makes them vulnerable to most environmental and ecological changes especially predation (Goudswaard et al., 2008). Haplochromines are known to spend more time and energy protecting their young ones which sometimes leads to their capture by predators. The rate and sequence of haplochromine decline within the lake was determined by the relative abundance, their adult size as well as their habitat overlap with Nile perch (Witte et al., 1992). The Nile perch being a better competitor and a predator of the haplochromines, the habitat overlap is disadvantageous to haplochromines as this increases their interaction with each other. The rate of disappearance differed among the different feeding guilds; the relatively large piscivores, insectivores and molluscivores were the first to disappear from the catches. The small detritivores and zooplanktivores declined at lower rates (Witte et al., 2007; Seehausen et al., 1997). This could be largely due to the size; larger fish are easier to spot and pursue by the predatory Nile perch. The exotic Nile tilapia is also suspected to have had negative effects on the haplochromine biodiversity through hybridization, overcrowding, competition for food, as well as the introduction of parasites and diseases from their native environments (Awiti, 2011). Some satellite e.g. Lake Kanyaboli and the

Yala swamps have been hypothesised to be refugia of haplochromine species.

The African catfishes

Catfishes in Lake Victoria are declining over the years. The numbers of these indigenous catfishes have decreased drastically since the beginning of 1980s (Goudswaard and Witte, 1997; Dadzie and Ochieng-Okach, 1989). The overall catfish stock in Lake

Victoria was estimated at 90 tonnes,the standing stock of Bagrus docmak was estimated to be

2788, 22131 and 14766 tons in the Kenyan, Tanzanian and Ugandan portions of Lake

Victoria, respectively in the 1970s. Yearly catches fluctuated between 500 and 17000 tons, but in 1988 decreased to less than 200. From Kenyan waters, 1000 to 1800 tonnes landed annually until 1983 followed by a decline (Kudhongania & Cordone, 1974; Goudswaard and

Witte, 1997). The decline has been attributed to the introduction of Nile perch and the ecological changes that have taken place within the lake over the years deoxygenation of deeper waters and the decline in the haplochromine cichlids which constituted an important food source for this fish. For example, 1980s B. docmack was known to feed predominantly on haplochromines but the diet was observed to have changed to Ratrineobola argentea and ologochaetes in the recent years most probably due to the decline in the number of haplochromines in the lake. Until the 1980s B. docmak, C. gariepinus and Schilbe intermedius were the top predators within the lake before the establishment of the predatory

Nile perch (Goudswaard and Witte, 1997). Xenoclarias eupogon was estimated to be 447 tonnes in the whole lake in the early

1970s. The catch rates have declined over the years from 18, 0.6 and 0.3 (number of fish caught) per hectare in 1984, 1985 and 1986, respectively (Goudswaard and Witte, 1997) and currently the fish is thought to have gone extinct. Synodontis victoriea and S. afrofischeri are still present in small numbers in shallow areas of the lake (Bwanika et al., 2006). These are mostly considered as by - catches in the fishery of R. argentea- a dominant cyprinid within the lake. S. intermedius and C. gariepinus are the least affected of the catfishes in the lake and this could be due to smaller habitat overlap with Nile perch than the other catfish species.

S. intermedius is partly pelagic, while C. gariepinus live in water bodies surrounding the lake thus can get their way back into the lake through river inflows and boosting their numbers within the lake (Goudswaard and Witte, 1997). S. intermedius was estimated to be 646 in the

1969 - 1970 (Table 1) and the number continue to decline over the years. The catches of these fish are occasionally included in the catch data as they were considered to be of low commercial value. This therefore makes the estimation rather difficult. The other threat facing most African catfish species especially S. intermeduis and S. victoriea is the gill net fishing in the river mouths especially during rainy seasons. This leads to the elimination of the gravid male and female fish migrating upstream to spawn. Kees et al, (1997), however argue that there is no indication that overfishing led to the decline in catfishes in Lake

Victoria especially in deeper waters.

The African lungfish (Protopterus aethiopicus)

The African lungfish (Protopterus aethiopicus) (‘Kamongo’ in Luo) is a special kind of fish especially among the communities living around the lake. Its snake like appearance and strong taste couple with the lower bone to flesh ratio places it in a particular category for fishermen and consumers. The decrease in the number of African lungfishes could be as a result of the conversion of most wetlands which served as their refugia to agricultural fields. Also harvesting of nest-guarding male lung fish could have contributed to the decreased recruitment of the young ones leading to decline in their numbers within Lake Victoria

(Goudswaard et al., 2002). Other possible reasons for the decline of the lungfish could be the impact of Nile perch, decline in food abundance, and habitat degradation. The decline has been demonstrated by Goudswaard et al., 2002 , who showed that there was a decline in the catch of lungfish from 67.5 Kg/ha to 5.5 Kg/ha between 1973 and 1986 while between 1986 and 1990 the catches decreased from 0.3 to 0.07 (Table 1). Not much research has been conducted especially on the culture and propagation of lungfish in captivity. There is therefore need to protect and manage their dwindling populations within the lake. Table?

The tilapines

Some tilapines indigenous to Lake Victoria and its affluent rivers like Oreochromis variabilis have also come under serious threat (Maithya et al., 2003). This species together with the native O. esculentus provided a lucrative fishery within the lake in the early 1960s but has declined considerably over the decades due to the various changes within the lake like predation from the introduced Nile perch as well other environmental and ecological changes over the years (Goudswaard et al., 2002). The number of tilapiines decreased in the 70s, and increased in the late 1990s and around 2000 (Table 1 and 2). This could be a result of the introduced Nile tilapia which also led to a decrease in the population of O. variabilis and O. esculentus but an increase in the landings of the tilapiines in general. The contribution of O. variabilis decreased from 26 fish caught per hectare in the early 1970s to less < 1 in the late

1980s, and the subsequent years. Although data on these two species are scanty, the data from fish landings around the lake show a decline in their numbers.

According to Sitoki et al., (2012), eutrophication has led to increase in blue green algae which has replaced the diatoms; the preferred diet of O. variabilis (Maithya et al., 2012). Nile tilapia (O. niloticus) was introduced into the lake in the 1950s to enhance the declining tilapiine fishery (Njiru et al, 2008). The ecological effects of this introduction just like that of Nile perch was not taken into consideration (Njiru et al., 2004). Being a superior competitor, O. niloticus has gradually replaced O. variabilis and O. esculentus ( Awiti, 2011;

Njiru et al., 2005; Aloo, 1991). The introduction of O. niloticus and Tilapia zillii has led to the replacement of the these endemic species (O. esculentus and O. variabilis) with possible hybridization as speculated by Lowe-Mc Connell, (2009). It was observed that the contribution of these two fish species started to decline gradually to a point of disappearance in the catches within the lake since the establishment of the two introduced species (Lowe-

Mc Connell, 2009). Other reasons cited for the decline in the numbers of O. esculentus within the lake, (apart from competition from Nile tilapia) is the replacement of Aulucosira by the less nutritious blue green algae (Sitoki et al., 2012). The replacement has been due to the eutrophication as the blue green algae can tolerate the high nutrient conditions as opposed to the former which is sensitive to nutrient enrichment.

Table 1: Contribution of the different species (number of fish caught per hectare) in Lake Victoria over time (adopted from Balirwa et al., 2003; Goudswaard et al., 2002a; Goudswaard et al., 2002b) and Goudswaard and Witte, 1997)

1973 1984 1985 1986 1987 1988 1989 1990 2000 B. docmak 23 37 12 2 1 0 0 S. afrofisheri 10 33 6 6 5 1 1 S. victorianus 67 163 80 0 0 0 0 S. intermedius 46 89 72 54 26 12 62 Lungfish 67.5 5.5 0.07 O. variablis 26 15 2 2 0 0 - 0 O. esculentus Haplochromine From 1955 to 128 3 4

s L. victorianus From 204 to 20 0 0

Table 2: Contribution (Metric tonnes) of the various fish species in the fish catches from

Lake Victoria (Adapted from Balirwa et al., 2003)

Taxa 1966-1967 1976-1977 1986-1987 2000 Tilapiines 17,747 2480 5772 30,530 Bagrus 6646 4645 8173 152 Protopterus 2627 2035 309 469 Barbus 813 330 85 0 Synodontis spp 122 305 28 127 Haplochromines 1955 1280 3 4 Labeo 204 20 0 0

2.0. Economic losses and possible conservation strategies that could be adopted

Lake Victoria fishery provides employment to over 1 million people and provides over 500,000 metric tonnes of fish per annum (Njiru et al, 2008). The main contributor to this production is Nile perch and Nile tilapia, although indigenous fish species included above contribute to some extent to the yield. The economic potential of the indigenous fish species of Lake Victoria is enormous. Although not explicitly recorded, these fish species are still the favourite of many people living around the lake region. Labeo, lungfish and catfishes are highly regarded. Synodontis spp are currently used as ornamental fish which when caught live command high price. The loss of these species will certainly lead to huge losses both in terms of income and food.

The aquaculture potential of these fish species particularly O. esculentus, O. variabilis and L. victorianus has been explored by several researchers over the past few years.

In Kenya for example, research has been going on the best culture systems and practices and the viability of breeding and propagation of Labeo in captivity (Abwao et al.,2014; Orina et al., 2014; Kembenya et al., 2016). Several studies have been undertaken for culture which showed that they can be cultured in ponds with equally good growth rate as tilapia (Mokoro et al., 2014; Oyoo-okoth et al., 2011; Wairimu et al., 2008). In addition, hatchery-produced L. victorianus larvae can be transported to culture centres for over 8 hours with very insignificant mortalities (Outa et al, 2014, unpublished data) which shows that fingerlings are resistant to handling stress which are vital for re-stocking programmes. In Benin, L. pervus has been reared under various conditions with (survival rates of up to 98% and specific growth rate of 15.5%day-1 (Montchowui et al., 2012) These data showed that Labeo can be propagated in captivity and enhancement of wild stock is possible.

The culture potential of O. esculentus, O. variabilis has been carried out by some farmers with the aid of researchers in Kenya with Charo-Karisa and Maithya, (2010), recording up to over 50% survival rates and mean weight of over 60 grams after 5 months of rearing in ponds. The relatively good growth performance of O. esculentus and O. variabilis in different ecological zones within the Lake Victoria basin indicates the viability of the species for culture which could then be used for propagation of fingerlings and subsequent restocking into the lake to boost the dwindling populations. The growth of most of these indigenous species is very slow, thus, fish farmers should be cautioned before starting economic ventures on these species. As pointed out by Charo-Karissa and Maithya, (2010), several issues require strict consideration in utilizing endangered species even if the objective is to conserve them. These include the need to maximize effective population size when carrying out hatchery operations as well as ensuring that the populations in the original refuge are left to thrive. Maithya et al., (2003), however observe that, as long as O. niloticus dominates in

Lake Victoria and changes in water quality continue unchecked, the Nile perch continues to thrive in the lake, and habitat degradation continues, restocking into the lake is not a viable means of conservation. Hybridization particularly between O. niloticus and other tilapiine species is another challenge that could be faced. However, for sustainability, these interventions should assume that these species could be conserved and used as a useful resource. The other possible conservation measure could be the protection of the refugia especially within the and the satellite lakes, e.g. Lakes Kanyaboli, Sare and

Kambonyo, which are identified as refugia of O. variabilis and O. esculentus. (Aloo, 2003).

Aloo (2003) found no hybridization in these satellite lakes, which means that the strains of these two species are still pure. These areas can therefore be used as sources of pure strains and brood stocks for propagation. Whatever conservation measures are put in place, the most important step that must be taken is the regulation of the fishing pressure within the lake through formulation and enforcement of laws and regulations by the concerned institutions.

These regulations should be harmonised for the three riparian countries (Kenya, Uganda and

Tanzania). Lack of harmonization of regulations regarding resource management has been a major problem in the management of the fisheries resources within the lake (Njiru et al;

2008). This has been more serious on the regulations regarding gear selection and usage within the lake with each country applying its own rules and regulations at times conflicting with those of the other countries sharing the lake.

Conclusions and recommendations

The loss of biodiversity of fish in Lake Victoria are mainly due to loss and degradation of habitat, eutrophication, predation and competition from introduced non-native fish species (Nile perch and Nile tilapia) and in some cases, unsustainable use of the lake such as overfishing or use of wrong fishing gears. These if not checked will lead to further decline in numbers of fish species and even extinction. There is need therefore for further research especially on the biology and ecology of these fish species coupled with concerted efforts to formulate policies to ensure sustainable utilization of the resources of the lake.

Breeding and culture of the endangered species as a means of establishing ‘seed banks’ for the endangered species is an option that needs expansion, exploration and research.

Fingerlings produced in these seed banks can then be re-stocked into the lake to boost the wild population. References

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