Section 3 Advances in Catfish

### **Chapter 3**

Perspective Chapter: Species Diversity and Distribution of Catfishes and Their Current Contribution to Global Food Security

*Don Felix Ouma and James E. Barasa*

#### **Abstract**

Ranking fifth in global aquaculture production of farmed fin fishes, with a total tonnage of 5, 518 878 metric tons worth US\$ 10 569 972 Billion, Catfishes are exceptionally important as a seafood product. They are an especially important food resource in developing countries, more so since their farmed production does not require sophisticated technology. The diversity and natural distribution of catfishes are documented. Farmed production of *Pangasianodon hypophthalmus* in the Mekong delta and *Ictalurus punctatus* in China is reviewed as global success story in the culture of catfishes. Important lessons from these ventures are drawn for the culture of clariid catfishes, the dominant group farmed in Africa. Amongst this family, the African catfish, *Clarias gariepinus* (Burchell 1822) is the most widely cultured species, due to its hardy nature. However, its culture is constrained by insufficient seed supply, due to poor survival of fingerlings. These challenges are brought to the fore, so that future research efforts explore strategies of countenance, in order to increase food fish production, incomes, and livelihoods in Africa.

**Keywords:** catfishes, species diversity, clariids, survival, seed production, *Pangasius*

#### **1. Introduction**

#### **1.1 Diversity of Catfishes**

Catfishes are a diverse group of ray-finned fish named for their prominent barbells, which resemble cat whiskers. Catfishes belong to the Phylum Chordata, class Actinopterygii, and of Order siluriforms. The group has about 40 families distributed around the globe. Despite their name, not all catfishes have prominent barbells, some members of the order siluriforms are defined by features of the skull and the swim bladder. They are most diverse in tropical South America, Africa, and Asia, but more


#### **Table 1.**

*Families of Catfish with the number of valid species in each family.*

than half of all catfish species are to be found in America. Catfishes are important biodiversity resources, playing important ecological roles in food chains in aquatic ecosystems. Similarly, they form important food fish for local communities and contribute to income generation and livelihoods (**Table 1**). According to [2] the most cultured among global catfish populations are the Amur catfish (*Silurus arsotus*), Channel catfish, *Ictalurus punctatus*), Stripped catfish, *Pangasianodon hypophthalmus,* and the African catfish (*Clarias gariepinus*). Africa has ten siluriform families [2–4], which include: Amphiliidae, Ariidae, Austroglanididae, Bagridae, Clariidae, Claroteidae, Malapteruridae, Mochokidae, Plotosidae, and Schilbeidae. Catfishes group into 32 families, distributed globally, with currently 3,407 valid species [5]. Like the spectacular haplochromine cichlids of the Great lakes of Africa, some groups form species flocks in the habitats where they occur. These include *Bathyclarias*, endemic in Lake Malawi [6], where they comprise up to 12 species [6].

According to [7], catfishes are distinguished by pairs of barbels, cylindrical body without scales, largemouth, pectoral, and dorsal fins that bear spines. For the clariid family, the key distinguishing feature is the suprabranchial organ formed by arborescent structures from the second and fourth-gill arches [8–10] and flat dorso-ventrally flattened skulls. Clariidae is naturally distributed in Asia, Syria, and Africa. In Africa, this family has 13 genera and 74 species. Amongst the species include the *Heterobranchus* species, *Dinotopterus*, *Bathyclarias*, *Clarias gariepinus, Clarias anguillaris,* and other nominal species of *Clarias* in Africa. The clariids are mostly found in the muddy bottoms where they graze on variety of food materials hence regarded as omnivores. Some clariids such as *Xenoclarias* and *Dinotopterus* are found in Lakes Tanganyika, Victoria, and Malawi, the upper Congo, the middle and the upper Zambezi, the Okavango, L. Ngami, the Chobe, the Cunene and the Quanza in South Africa, and other Great lakes of Africa. The Gymnallabes live in turbulent well-oxygenated rivers of the Congo, but they lack the respiratory accessory organs. The Bathyclarias species are also found in Lake Malawi [10, 11] (**Table 2**).


#### **2. Diversity and distribution of catfishes**




*Perspective Chapter: Species Diversity and Distribution of Catfishes and Their Current… DOI: http://dx.doi.org/10.5772/intechopen.106706*




#### **Table 2.**

*Families of catfishes, common species per family and their distribution. Although not complete, this table captures the diversity of catfishes, and where each species is distributed globally.*

#### **3. Contribution of catfishes to food security in Africa**

According to [29], a total of 27 catfish species were farmed in 86 countries worldwide in 2017, with a total production of 5, 518 878 tonnes, worth US\$10, 569 972 billion of farm gate value. A large percentage of this production is from Pangasiid and Clariid catfishes, which contributed 51% and 24%, respectively, to the total annual production [29], which represents diversity and resilience of these two groups. The Mekong river harbors up to 16 species of *Pangasius*, grouped into 4 genera of *Helicophagus*, *Pangasianodon*, *Pangasius,* and *Pteropangasius* [30]. However, only 2 species are farmed in the river-based capture aquaculture: the river catfish (or sutchi or tra catfish) (*Pangasianodon hypophthalmus*) and Bocourt's catfish (*Pangasius bocourti*) [31]. Of these species, *P. hypophthalmus* is the most commonly cultured species, due to its higher fecundity, which occurs mainly at the surface, therefore, its larvae are easily caught for seeds [32] and exploit diverse food resources [33]. The culture of *P. hypophthalmus* in the Mekong delta of Vietnam grew at an average annual rate of 37% between 1997 and 2008, reaching a total annual tonnage of 1.4 million tonnes in 2009 [34], with an export turnover worth US\$1.85 billion in 2011. This rapid increase in production of Vietnamese farmed *Pangasius*, an iconic industry directly employing over 180,000 people, was fueled by high and expanding market demand in over 100 countries, especially in the USA and Europe [34]. Despite adverse media


*These measures significantly spurred production, raising the industry from artisanal to a commercial export-oriented one, supplying over 100 countries globally. Source: [36].*

#### **Table 3.**

*Historical transformation of the Vietnamese striped catfish farming in the Mekong.*

reports of possible poison levels in *Pangasius* imports from Vietnam, demand for these fish products skyrocketed, buoyed by favorable reports of risk assessment and management, through toxicological risk surveys [35] (**Table 3**).

With current production of cultured *P. hypophthalmus* in Vietnam equivalent to 65% of European aquaculture production [37], the industry provides a microcosm of what production efforts for related species need to be put in place to spur production. Starting as a small-scale backyard activity, farmers grew the fish in ponds, with limited input and harvests [38]. This transitioned to the use of pens and cages in the Mekong, with use of poor-quality seeds caught from natural aquatic systems, especially from the Cambodian waters of the confluence of the Mekong, Bassac, and Tonle Sap Rivers [39]. However, with the ban on the collection of natural seed stocks for the species by Cambodian authorities in 1994 [40], production declined slightly, but this challenge in seed availability stimulated a focus on seed production technology. Similarly, challenges associated with water flow under cages led to a transition to pond culture along the lower reaches of the Mekong. This, infused with technological improvements in the artificial propagation of seeds, vertical integration of the pond farming systems, and processing of the final product, significantly transformed production between 1997 and 2007 (**Figure 1**).

Therefore, although a majority of the farmers were small-scale, with up to 81.9% of the 5,393 farms being less than 1 ha in size, high production was still achieved and maintained (**Figure 2**) [38].

#### **3.1 Factors contributing to a rise in farmed Vietnamese striped catfish in the Mekong**

The production units were vertically integrated, with seed production, fry production, fry to fingerling, and grow-out units being distinct, in different locations and

#### **Figure 1.**

*Total tonnage of farmed* Pangasianodon hypophthalmus *produced and exported in Vietnam, from 1997 to 2010. Source: [38].*

setups. This ensured specialized labor and effort (cluster of operations) increased efficiency of the sector and effective dissemination of technology to farmers [38]. Similarly, special attention was given to seed production and broodstock management at hatcheries. The major technique that revolutionized the sector was the development of artificial propagation of tra catfish seeds [42], and the dissemination of the technology to all hatcheries in the Mekong. This ensured the availability of adequate highquality seeds for the enterprises, following the ban on collection of natural seed stocks in the Mekong. Apart from this, a large number of hatcheries were developed, ranging from small-scale or back yard to commercial scale or large establishments (0.2 to 15 ha) [43]. There were 93 hatcheries for tra catfish in the Mekong delta, producing up to 818.3 million hatchlings annually under optimal operations of 29 cycles of fry production annually [44]. Many hatcheries maintained a large number of broodstock (up to 29,200) so the frequency of reusing a brooder was very low [38]. This reduced the rate of inbreeding and genetic drift, two processes that often negatively impact quality of seeds or fry, and this consequently improved the quality of the seed. Many hatcheries also replace their brood stock frequently [43], with stocks from their own extensive farms, neighboring grow-out farms, or from natural sources [38, 43]. Continuous improvement of seed quality is undertaken, for instance through selective breeding program for the species that has been initiated [45]. Feeding regimes in nursery units are also quite improved, ranging from recommended practices of live feeds such as

#### **Figure 2.**

*Annual production of farmed striped catfish,* Pangasianodon hypophthalmus *in Vietnam 2010 to 2019, the lead global producer of farmed Pangasiid catfishes. Annual production steadied from 2010 to 2019, mainly because of commitment of farmers and an expanded export market for the product. Source: [41].*

Moina, or other such natural feeds for larvae, to commercial diets for fingerlings. The feeding ration was 5 to 18% body weight at a frequency of 4 to 8 times daily [43]. Grow-out systems were mainly operated by small-scale farmers (72%) [46], comprising deep ponds averaging 2.0 to 6.0 m, with a water depth of 3.5–4.5 m, with a high stocking density of 18 to 125 fish m–<sup>2</sup> depending on seed availability and financial ability of farmers. Average yields ranged from 70.0 to 850 t ha<sup>1</sup> crop<sup>1</sup> , although the pond area and productivity per unit area have been increasing since 2000 [46].

Growth in the production of *P. hypophthalmus* was also boosted by export-oriented markets, with the USA being the main market in the 1990s. Increasing imports of tra catfish to the USA were boosted by the admission of Vietnam to the Asia Pacific Economic Consortium (APEC) block, and the dropping of tariffs on raw seafood [47]. The increased imports of tra catfish affected markets of the local ictalurid catfish and occasioned trade restrictions via new laws against tra catfish and renegotiation of bilateral agreements against the species [48]. These restrictions were worsened by negative internet and media campaigns against striped catfish industry of Vietnam [49]. However, with the explosion in the production of striped catfish in the 2000s, export market diversified, to about 136 countries between 2002 to 2008 [38], with the European Union being the major market [38]. This phenomenal growth occurred despite trade restrictions by the USA due to negative publicity about *Pangasius*.

Expanding export markets was due to deliberate efforts by Vietnamese authorities to promote production while exploring alternative markets. Some of these efforts included: certification of groups of small-scale operators. Certification is a procedure by which a certification body gives written or equivalent assurance that a product, process, or service conforms to specified requirements and is carried out by competent and accredited body [38] (**Figure 3**).

Certification is important as it ensures that food quality and safety are achieved with respect to internationally traded food commodities and that the production systems comply to accepted norms and are socially responsible. Similarly, certification of a product ensures that farming systems have minimal environmental impact and that the production systems are sustainable. Certification also assures markets (buyers, retailers, and consumers) that the fisheries products are safe to consume and originate from aquaculture farms or capture fisheries adopting responsible management practices [38].

Certification of tra catfish farmers, therefore, assured the international market of the safety and quality of the product, and the confidence associated with this spurred

#### **Figure 3.**

*Global Production of farmed striped catfish,* Pangasianodon hypophthalmus *2010–2018. Intensification of production and use of technology, high-quality seeds produced from hatcheries' commercial diets, and processing of the product using global quality control systems commercialized the industry. Global production was averaging 2.4 million tons, from China,Thailand, Cambodia, Myanmar, Lao PDR, Vietnam, and Bangladesh. A large proportion of this came from Vietnam, with many farmers utilizing the large Mekong delta of Vietnam. Source [41].*

demand for the product. Related to marketing of the product, the Vietnamese Government adopted negotiation with organizations such as the WWF, to address the biased negative publicity against tra catfish, and the WWF removed the species from its red list of endangered species. Similarly, Government encouraged farmers to adopt BMPs, cluster management approaches, and compliance to responsible farming practices to deter future problems. Due to the very marginal profits made across the tra catfish value chain, improved processing operations increased efficiency of processing, so that a relatively small amount of fish was required to produce 1 kg of processed fish. Production was also sustained by increased turnover or high production by farmers, exploiting the benefits of economy or scale of production [38]. This was further boosted by authorities implementing the guaranteed price scheme at each link of the value chain, to cushion operators against large fluctuations in prices [50]. Generally, there was deliberate action to maintain a suitable quality of the product, with desirable nutritional profile, as well as low content of pollutants, such as mercury, organochlorine pesticides, and polychlorinated biphenyls, consistent with the European rapid alert notification system [38]. Such actions included reduced use of veterinary drugs and other restricted or banned chemicals in the value chain of the fish by farmers and other operators, in compliance with food quality and food safety regulations.

Despite the rapid explosion of tra catfish culture in the Mekong, the industry has had very minimal environmental impacts on the Mekong ecosystem [38]. This is because only 2% of the waters of the Mekong pass through the ponds, and therefore the impact of aquaculture on the water quality of the river is minimal since sedimentation, mineralization, and infiltration occur in the ponds [51]. Further limitation of environmental impacts is achieved through the use of sludge from ponds as fertilizer for rice paddies, which helps to achieve environmental and economic sustainability for the farmers [52]. Similarly, hatchery-reared stocks of tra catfish have not impacted natural populations of the species and related fishes in the Mekong, through hybridization from escapees [53].

#### **3.2 The Channel catfish, Ictalurus punctatus (Rafinesque, 1818)**

The channel catfish (*Ictalurus punctatus*) is a member of the family Ictaluridae in the order Siluriformes. The native range of the Channel catfish or the North American Channel catfish, *Ictalurus punctatus*, is the southern Canadian Prairie Provinces south to the Gulf States, west to the Rocky Mountains, and east to the Appalachian Mountains [54]. Further, it extends to St. Lawrence River and its tributaries from southern Quebec through to Ontario including the Ottawa River and its tributaries, all the Great Lakes except Lake Superior, in southwestern Ontario and the southern part of Manitoba (**Figure 4**). This extends to Susquehanna River and the Florida Peninsular. However, the fish has been introduced in Georgia, North Carolina and South Carolina, and in most of the USA, including the Pacific and Atlantic drainages [54]. It is also widely introduced in Europe, Japan, and China (**Figure 4**). Its large size and excellent taste make it a popular target of anglers. Its high fecundity, tolerance to extreme environmental conditions, and resistance to diseases make it an excellent species for commercial cultivation.

The congener, Blue catfish, *I. furcatus*, and the hybrid between *I. punctatus* \* *I. furcatus*, are also important in culture [56], and the three contribute to more than 60% of total aquaculture production in the USA, especially in the southern states of Mississippi, Louisiana, Arkansas, and Alabama [57]. The US catfish industry peaked in

#### **Figure 4.**

*Global distribution of the North American Channel catfish,* Ictalurus punctatus*. Countries culturing* Ictalurus punctatus *are shown in orange color. Source: [55].*

2003, but declined later, in part due to competition from the Vietnamese catfish imports.

Sizeable fingerlings are stocked in fertilized ponds. During growth, fish of bigger size are intermittently harvested for market, and an equal number of fingerlings is added to ponds to replace the harvested fish. Therefore, multiple-batch production is often adopted, although fish grow faster in single-batch stocking [58]. So a pond often has fish of different sizes, and cropping for market is frequently carried out, to supply the market steadily, and also control flooding the market with fish and negatively affect fish prices [55]. This is maintained for several years, without draining ponds. Initial feeding ration is about 50% body weight, which is reduced gradually, to 3–4% body weight. However, water quality in ponds is monitored frequently, and aeration of water is carried out, to ensure the fish under high stocking density do not suffer stress, disease outbreaks, and mortality. Apart from ponds, fishes are also reared in cages, raceways, and tanks (**Figure 5**).

#### **3.3 The Culture of Channel Catfish in China**

The Channel catfish, *I. punctatus* was introduced to China from the USA in 1984, and successful artificial propagation was achieved in 1997, to support seed production for commercial culture. Rapid growth in the culture of the species in the country was recorded, due to several factors. Domestic consumption of the species reached 130,000 tons in 2013, of which 120,000 tones were fresh fish while 10,000 tones were processed [59]. The culture of the species has led to the growth of associate industries, strengthening synergies in the sector. For instance, due to the high demand for Channel catfish in many provinces of China, companies such as the Gaobazhou Aquatic Products processing company, promote value addition to the fish products, boosting sales, while simultaneously creating employment opportunities for locals [60] (**Figure 6** and **Table 4**).

**Figure 5.** *Annual average global production of farmed Channel catfish,* Ictalurus punctatus *from 1980 to 2010. Source: [29].*

#### **3.4 Seed production to support the expansion of Channel catfish culture in China**

Following the importation of *I. punctatus* to China in the 1980s, artificial production was successfully initiated and perfected, assuring the sector of sufficient seed production. However, production of adequate amounts of quality seed was affected by degradation of germplasm quality, inbreeding, variation of germplasm, reduced growth rates of fry, and increased incidence of diseases [60]. In order to address these challenges, Government authorities established the National Channel Catfish improved variety bases in Sichuan, Hubei, and Anhui, to undertake breeding schemes for improved varieties of *I. punctatus* for culture [60]. The result of these efforts was the development of improved strain of catfish named the Jiang Feng No. 1 [60], whose growth rate is 22.1 to 25.3% greater than that of any other strain [60]. Later, 2 improved lines were developed by screening different populations for economic gain and growth performance, using the Best Linear Unbiased Prediction (BLUP) method. This led to the development of two hybrid lines with high growth rates, resistance to diseases, and survival. Further research on this focuses on identifying populations of high genetic variation and quantitative trait locus (QTL) of economic interest, to develop superior strains for use by farmers [63]. In line with these, fish seed breeding centers, together with other hatcheries for farmers adopted best management practices, especially focusing on managing quality of broodstock. Most hatcheries maintain a large number of brood fish, ranging from 30,000 to 50,000. This is necessary

#### **Figure 6.**

*Annual Farmed Channel catfish,* Ictalurus punctatus *production in China, 2003 to 2010. Source: [61]. There was a rapid increase in production between 2005 to 2013, because of artificial propagation of seeds, and improvement in quality of seeds and strains used by farmers.*

because a large sample size from which breeding pairs of fish are drawn maintains high genetic variation that positively impacts seed quality. Due to these improvements, seed production for Channel catfish farmers reached 800,000,000 to 1 billion, and rose to 1.5 billion fry in 2013 [60], helping to spur a vibrant culture industry for the species.

#### **3.5 The culture of African Catfish,** *Clarias gariepinus* **(Burchell, 1822)**

While the different families of catfishes are widely distributed in natural aquatic ecosystems in Africa and are landed from fisheries by local fishermen, the African Catfish, *Clarias gariepinus* is the most commonly exploited species. There are 58 species of *Clarias*, of which 33 are in Africa, while 25 are distributed in Asia [21, 64]. In Africa, apart from *C. gariepinus*, *C. anguillaris* and *Heterobrachus longifilis* are also common in aquaculture, although these 2 are of restricted distribution [64], mainly in the Nile and West Africa. Other non-*Clarias* clariid catfish genera in Africa include *Bathyclarias* (in Lake Malawi) and *Gymnallabes typus* (in the lower Niger River and Cross River basin of Nigeria and Cameroon).

A systematic revision of 120 nominal species of *Clarias* by Teugels reduced these to only 32 valid species [65]. In a related study, Teugels [66] documented 74 species of African clariid catfishes within 12 genera. The description of two species of *Xenoclarias* as *Clarias eupogon* (Norman, 1928) and *Xenoclarias holobranchus* (Greenwood, 1958) was changed to *Xenoclarias eupogon* (Gee, 1975) using more samples, as a monotypic genus. Similarly, three clariid genera, *Clarias*, *Clariallabes,* and *Heterobranchus* occur


#### **Table 4.**

*Historical milestones in the growth of the Channel catfish culture in China.*

in Southern Africa [67], with *Clarias* having 6 species, while *Clariallabes* and *Heterobranchus* have a single species each [67]. In Southern Africa, a total of six *Clarias* species exist: *Clarias gariepinus*, C. *liocephalus*, *C. cavernicola*, *C. theodorae*, *C. stappersii*, and *C. ngamensis* [67]. On the other hand, six *Clarias* species inhabit Central Africa: *C. gariepinus*, *C. platycephalus*, *C. camerunensis*, *C. gabonensis*, *C. buthupogon*, and *C*. *angolensis* [68]. In lower Guinea, a total of 13 *Clarias* species are documented, including *C. gariepinus*, *C. anguillaris*, *C. agboyiensis*, *C. gabonensis*, *C. buthupogon*, *C. angolensis*, *C. pachynema*, *C. submarginatus*, *C. platycephalus*, *C. maclaroni*, *C. ajensis*, *C. longior,* and *C. camerunensis* [69]. Similarly, several *Clarias* species exist in Lake Victoria and its influent rivers in East Africa. Apart from *C. gariepinus*, several species including *C. liocephalus* (Boulenger 1898), *C. alluaudi* (Boulenger 1898), *C. theodorae* (Weber 1897), *C*. *werneri* (Boulenger 1906), and *Xenoclarias* also abound [70].

In Asia, 3 Asian clariid catfish species are used in aquaculture: *Clarias batrachus* (Linnaeus, 1758) in India [71], *C. macrocephalus* in South-East Asia [72], and *C. fuscus* (Lacep'de, 1803) in Taiwan and Hawaii [73]. *Clarias batrachus* also inhabits Southern Thailand in Malay Peninsula, Mekong, and Chaophraya River basins. *Clarias magur*

(Hamilton, 1822) is also present in the Malay Peninsula and India, while *C. nieuhofii* (Valenciennes, 1840) inhabits South East Asia, successfully tried as an aquaculture species [74].

While these descriptions may not be quite accurate and require urgent revisions, they illustrate the diversity of *Clarias*, which is often unrecognized and undescribed, yet extremely important as biodiversity for local economies, and food resources for local communities. Similarly, some of these clariid species could be useful aquaculture candidates, to help overcome some of the challenges of *C. gariepinus* as a farmed species. From the diversity of clariid catfishes, it is also clear that there are two groups: the large and small-sized *Clarias* species. The large *Clarias* is represented by *C. gariepinus*, while the small group includes most other species across different regions of Africa. *Clarias gariepinus* has been widely translocated, at least in 35 countries, mainly for culture [64]. These translocations often ignore existing laws that ban transfer of fish across drainage basins [75] and pose risk to existing native stocks or species, due to hybridization. Examples of hybridization between different *Clarias* species include *C. anguillaris*\**C. gariepinus* in Nigeria [76] and a hybrid of *C. macrocephalus* (better taste and culinary attributes) \**C. gariepinus* (faster growth and higher resistance to diseases). This hybrid is the main fish stocked for culture, because of faster growth and higher resistance to diseases, with its product valued at over US \$100 million in Thailand [77]. The introduction of *C. batrachus* and *C. macrocephalus* from Thailand to China, the Philippines, Taiwan, and Hong Kong led to the loss of endemic cyprinids from Lake Lanao, Mindanao due to predation and the displacement of native *C. macrocephalus* from Luzon [64]. Introgression of alleles from this hybrid into the genome of natural population of *C. macrocephalus* devalues the natural genetic resource of *C. macrocephalus* [78] and also causes decline in the natural stocks of *C. batrachus* (**Figure 7**) [79].

#### **3.6 Challenges facing the culture of** *Clarias gariepinus* **in Africa**

Although it is well recognized as a suitable fish species for aquaculture to meet food security, income generation, and livelihoods for local communities in Africa, annual cultured production of the species is low. FAO estimates that average production for farmed clariid catfishes was over.

300,000 tons, which was valued at nearly US\$400 million in 2006 [77]. Total production of *C. gariepinus*, the main farmed clariid catfish species, averages 200,000 tons in 2014 [41] (**Figure 8**). Diverse efforts to increase average production in many countries of Africa have not yielded much fruit, despite ample supplies of water, land, labor, and technical know-how, as well as diverse populations of natural germplasm (**Figure 7**).

The main challenge stifling the culture of *C. gariepinus* is poor survival of fry or larvae [81]. This reduces the quantity of fry produced by farmers at hatcheries, negatively impacting seed availability and supply for commercial aquaculture ventures. In East Africa, *Clarias* fingerlings have taken on an even bigger role and importance, being used as live baits for catching Nile perch and *Lates niloticus* in the Lake Victoria long line fishery activities [82]. It is reported that a total of 3 million *Clarias* live baits are required daily by *L. niloticus* fishermen on Lake Victoria [83], a demand that creates enormous opportunities for *Clarias* farmers and hatchery operators to generate income and livelihoods. Despite this, the supply of fingerlings from hatcheries in East Africa is very low, forcing bait traders to exploit natural populations for fingerlings. Harvesting fingerlings from natural populations is not environmentally

#### **Figure 7.**

*The main ichthyological provinces of Africa (Adopted from [80]. Except the Maghreb, Karoo and Cape,* Clarias gariepinus *is widely distributed in the rest of the Provinces on the continent.*

sustainable, with intermittent supply as availability is rain-dependent. This practice also exacerbates overexploitation of natural fish stocks, contrary to the need to conserve natural fisheries resources, especially for the Lake Victoria basin, whose endemic fish species already declined [84] due to many factors [82, 85]. Apart from endangering the health of fishermen who collect the fingerlings from the wild, this practice does not yield adequate numbers of fingerlings required quickly. It, therefore, involves a waste of time, and transport costs as fishermen have to venture into different parts of the lake, swamp, or river and spend many hours scouring different sites for catfish fingerlings. For sites within Lake Victoria, this task is especially complex and risky, due to dense mats of the water hyacinth, *Eichhornia crassipes* [86] that cover large areas of the lake.

In order to avoid these challenges and support the conservation of natural fisheries resources while simultaneously helping hatchery operators to generate income and livelihoods, artificial propagation of *Clarias* at hatcheries has been proposed and encouraged [85, 87–89]. However, despite the fact that artificial propagation of *Clarias* at hatcheries is well perfected, practiced, and documented, high mortality of *Clarias* fry at hatcheries still persists. In some hatcheries, mortality of more than 80% of hatchlings occurs, severely curtailing efforts of increasing seed availability for farmers. In some cases, the whole batch of incubated eggs fails to hatch, due to contamination with bacteria and fungi [90] in hatchery and egg incubation

#### **Figure 8.**

*Annual production of Farmed* Clarias gariepinus *in Africa, 2000 to 2014. Most of the production is from 3 countries (Nigeria, Uganda, and Ghana), as the lead producers on the continent, with most countries producing insignificant amounts of catfish annually. Source: [41].*

facilities. Over the last several decades, research efforts have concentrated on addressing poor survival of *Clarias* fry or fingerlings at hatcheries. These research efforts included studies on improving quality of diets for larval catfish [81, 91–93], expanding the range of *Clarias* production systems [94], control of bacteria and fungi in egg incubation units [95], as well as fry nursery units [96], and improving the choice of source population of brood stock used at hatcheries for propagation [88, 89], as well as management of elite lines of brood stock for seed production [86]. In this regard, hatchery managers and farmers need to understand that the use of poor quality broodstock of mixed ancestry or suffering low genetic variability yields seeds of poor quality [89] because of outbreeding depression that compromises the fitness of offspring [97]. Despite this suite of studies aimed at addressing the challenge of poor survival of *Clarias* fry or fingerlings, the problem is far from being comprehensively addressed, in order to achieve sufficient seed availability and supply. There is need to understudy seed production and supply in the farmed catfish industry of Asia, especially the Vietnamese striped catfish, *P. hypophthalmus* and the Chinese Channel catfish, *I. punctatus*. We suggest that future efforts in addressing seed quality and quantity in *C. gariepinus* aquaculture will have to focus on using improved strains. Techniques of improvement, such as selective breeding and genomic selection will need to be employed, and research in these fields need to be strengthened.

### **Conflict of interest**

The authors declare no conflict of interest.

## **Author details**

Don Felix Ouma and James E. Barasa\* Department of Fisheries and Aquatic Sciences, University of Eldoret, Kenya

\*Address all correspondence to: barkanoti@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 4**

## Advances in African Catfish (*Clarias Gariepinus*) Seed-Production Techniques in Kenya

*Jonathan Munguti and Jacob Odeke Iteba*

### **Abstract**

African catfish is one of the aquaculture species in Kenya and a potential source of cheap protein for human nutrition. However, the major hindrance in the culture of catfish is seed production. The high-mortality rate of fry and fingerlings experienced by hatchery operators has limited the access and availability of catfish seeds. This had resulted in low-annual average production of farmed catfish. To address these challenges, different methods have been employed to enhance its seed production. One of such methods is induced spawning followed by larval rearing by the use of live feed like *Artemia*, thereafter, fry rearing with dry formulated feed, sorting by size, and stocking in nursery ponds. This chapter, therefore, will review the different mechanisms that had been adopted to enhance the seed production of catfish thus boosting its production in Kenya.

**Keywords:** African catfish, seed production, induced spawning, live feed, aquaculture

#### **1. Introduction**

The African catfish (*Clarias gariepinus*), also known as the mud catfish (**Figure 1**), is a good candidate species for culture to boost fish production for both domestic and global markets, which will improve human nutrition and food security in Africa [2]. The hardy nature of catfish in terms of its use of supplementary feeds, high tolerance to water stress, and high market acceptance makes it a suitable candidate for culture promotion in Africa as noted by [2].

In Kenya, the African catfish, from a biological perspective, is undoubtedly the most ideal aquaculture species [3]. It is widely distributed, hardy, and thrives in diverse environments, such as lakes, rivers, and fish farms [3]. Although, catfish is the most suitable species for aquaculture in Kenya; it contributes only 18% of total farmed fish production compared to Nile tilapia, which contributes 75% of total production [4] as illustrated in **Figure 2**. This shows that the high potential for catfish culture had not been fully exploited and indicates certain challenges that need to be addressed.

**Figure 1.** *African catfish (*Clarias gariepinus*) (image source: [1]).*

*Clarias gariepinus* culture in Kenya is practiced as a small-scale rural activity [3]. The system is largely semi-intensive [5] and is done in polyculture with Nile tilapia to control its prolific breeding and increase production per unit pond area [6]. African catfish is mainly cultivated under mixed-sex semi-intensive systems in earthen and liner ponds. The ponds are fertilized with organic manure, and the fish are fed on supplemental feed [4].

As noted by [3], several opportunities are available in Kenya for the production of African catfish. These include high-nutritional value, availability of feeds, and ready market for the fingerlings among others. The demand for catfish fingerlings as

**Figure 2.**

*Cultured fish species production (in MT) in Kenya from 2010 to 2019; source: [4].*

#### *Advances in African Catfish (*Clarias Gariepinus*) Seed-Production Techniques in Kenya DOI: http://dx.doi.org/10.5772/intechopen.105665*

bait fish for the Nile perch fishery in Lake Victoria has attracted a lot of interest from fish farmers [7]. In addition to the local demand, presently there is a huge demand for catfish fingerlings (both for stocking and bait fish) in the neighboring countries (Uganda and Tanzania) [8]. Therefore, farmers can also target the regional market in addition to producing for the local market,

Although catfish is suitable for aquaculture production in Kenya, there are several challenges to its quick adoption as an aquaculture candidate by farmers as noted by [3]. The scarcity of high-quality fingerlings in hatcheries remains a major impediment to the commercialization of catfish culture [2]. Fish farmers are often forced to resort to collecting fish seed from the wild or purchasing poor-quality seed from hatcheries [7]. Technologies for African Agricultural Transformation (TAAT) Aquaculture compact also noted that besides poor-quality fish seed, fish farmers are confronted with the following challenges in producing catfish. These include low skills of fish breeders in Best Management Practices (BMPs), high fry, and fingerling mortality associated with cannibalism, predation, poor feeding, and the lack of knowledge on fish-health management among hatcheries [2].

Therefore, this review explores the different techniques for breeding and seed production of African catfish that have been developed and can easily be adopted by fish farmers in Kenya to boost the culture and production of catfish in the country.

#### **2. Review methodology**

The scoping review methodology [9] and systematic reviews approach were adopted in the present study to generate a comprehensive literature review on the advances that have been made in seed production of African catfish in Kenya. The literature review is focused on artificial propagation, use of living, and formulated feeds for feeding and catfish grading measures in the hatchery. To meet the set objectives, a wide range of keywords (closely related to African catfish production) were searched in online database tools and scientific domains of Science Direct, Research Gate, Google Scholar, and Web of Science. To further narrow and refine search, Boolean operators ("OR," "AND," and "NOT") were appropriately used in the various databases and search engines. The collected literature database was organized in excepts, copies, and notes according to topics. The current paper is a result of research publications that met the inclusion criteria for the review paper.

#### **3. Advances in African catfish (***Clarias gariepinus***) seed-production techniques**

#### **3.1 Artificial propagation**

According to [10], domestication of *C. gariepinus* can be traced to 1950's and the success in African catfish farming can be linked to the successful development of artificial-propagation protocols in the 1980's. African catfish breeds naturally during the rainy season in flooded rivers, inundated paddy fields, and earthen ponds [11]. The seed collection of this species from the wild is unreliable, time-consuming, and uneconomical for large-scale culture of this fish [11]. To overcome these problems, artificial propagation of catfish through induced spawning techniques at hatcheries is thought to be the only alternative to reduce exploitation pressure on natural populations of these indigenous fish species of the Lake Victoria basin [7]. Furthermore, this practice generates income and livelihood opportunities for farmers [12] as well as guarantees quality and adequate numbers of seeds [13]. As noted by [7] identification and isolation of high-quality catfish brood stock for use at hatcheries in artificial propagation in combination with improved husbandry for resultant fry could be a good measure to increase the availability of catfish seed and enhance its commercialization in Kenya.

As noted by [11], the developments of catfish artificial-propagation techniques have allowed farmers to profitably breed and culture this species that does not naturally reproduce under captive conditions. Over the last few decades, hormonal administration techniques have been used to induce final oocyte maturation and spawning that has allowed reproduction in controlled conditions [14]. Moreover, as reported by [15] induced breeding techniques have significantly contributed a lot to the expansion and diversification of the aquaculture industry. The *gonadotropin-releasing hormone (*GnRHa) and domperidone are the most popular compounds for induction of ovulation and spermiation in various fish species [13]. The introduction of GnRH analogs has been proven to be efficient in inducing maturation and spawning in many fish species, including catfishes [16]. Successful induced spawning depends upon the dosage of hormone injection, the stage of maturity of the fishes, and environmental condition, such as temperature, water currents, and rain as reported by [13]. As reported by [17], various commercially available synthetic ovulating agents in a ready-made form that contained GnRHa and dopamine antagonists, such as ovatide and ovaprim, are becoming easily accessible nowadays and found to be efficient and successful spawning agents in different fish species as noted by [18]. Successful spawning through a synthetic analog of GnRH has been reported in several air-breathing fish species including African catfish [13].

#### **3.2 Use of live feeds and formulated feed diets**

One of the suitability of African catfish for aquaculture arises from its acceptance of both artificial and non-specialized feeds, and the larval period is considered critical in their life history as noted by [19]. Successful larval rearing depends mainly on the availability of suitable diets that are readily consumed, efficiently digested, and that provide the required nutrients to support good growth and health [20]. Fish larvae often depend on live food, and in general, fish species like catfish have been reared successfully in aquaculture at the larvae period with fully digestive system at starting time of feeding. As noted by [21], live foods, besides their nutritional value, are highly digestible, easily detectable, and easy to capture by the fish larvae due to their swimming movements in the water column.

As reported by [21], the most widely used live food in catfish larvae culture is the brine shrimp (*Artemia salina)*. It is popular for mass production because of its viability over longer period of time and its ease of transport, due to its ability to form cysts. *Artemia* is also very nutritious to the larvae (>56% crude protein, 17% lipid and 3% carbohydrate) as noted by [22]. Zooplanktons, such as *Daphnia*, *Moina,* and rotifers are the other live food currently being used in Africa and other parts of the world. Besides being known to improve the flavor, color, and texture of fish that feed on them, they are valuable sources of crude protein, amino acids, lipids, fatty acids, minerals, enzymes, and carotene [23].

#### *Advances in African Catfish (*Clarias Gariepinus*) Seed-Production Techniques in Kenya DOI: http://dx.doi.org/10.5772/intechopen.105665*

In Kenya, hatcheries have recently adopted the use of biofloc technology (BFT) to enhance the provision of live feed to the fish larvae. The BFT uses the principle of nutrient cycling through complex bio-pathways to produce natural food for fish [24]. The working machines are the bacterial flocs that convert pond bio-wastes into edible nutrients for the cultured animals, thus it reduces feed cost by about 30% and ensures higher profitability as reported by [24]. BFT is useful for mass production of live food resources, which are indispensable for successful larviculture in hatcheries since they constitute organic particles, food debris, chemoautotrophic, and heterotrophic bacteria, which are nutritious and ultimately result in improved growth performances of fish [25]. As noted in a study by [26], the biofloc increased protein utilization efficiency, lowered the Food Conversion Ratio (FCR), and enhanced the fish-growth rate of Nile tilapia fish fry. These can also be applicable in the culture of catfish larvae in the hatcheries. For instance, [27] in their study reported that, though African catfish broodstocks maintained in the biofloc systems resulted in comparable fecundity and eggs quality to those broodstocks in the control systems, it significantly improved the larval quality and embryonic development rate. Moreover, culturing the larvae in biofloc systems improved their survival and final body length [27]. Nevertheless, absolute use of live foods as the diet for catfish larval rearing can be slightly alleviated by weaning with dry formulated fish feeds.

The use of dry feeds for catfish larval and fry rearing should satisfy the nutritional requirements of the species and should be readily accepted. As reported by [20], a fundamental aquaculture species considers dietary protein essential since adequate dietary protein significantly influences growth, fish survival, and feed cost. The main source of protein in aqua feeds remains to be fishmeal, as it contains a profile of highquality protein with balanced amino acid, and the high demand for it, along with supply fluctuation made fishmeal expensive [28]. As a result, relentless efforts have been made to substitute a fish meal with other cheaper sources of protein, such as the use of Black Soldier Fly (BSF) [29]. In Kenya as reported by [30], several protein sources of both animal and plant origins (blood meal, soybean, wheat bran, maize, and other formulated feeds) are being tested as fishmeal replacements and are in use by different aquaculture farms in the culture of catfish.

#### **3.3 Grading technique**

As reported by [31], cannibalism is another fundamental issue affecting the culture of catfish that can be addressed by adopting grading techniques. The *C. gariepinus* exhibits allometric growth patterns where larger fish have higher growth potentials than small-sized individuals [32]. Heterogeneous size distributions often lead to social dominance, which in turn results in aggressive behavior and cannibalistic responses [31]. This in turn increases their susceptibility to diseases and weakens the fishes making them more liable to cannibalism or death [33]. Therefore, to enhance profitability from catfish aquaculture production, strategies that are designed to reduce cannibalism should be explored.

As reported by [34], size grading practices is a common procedure used during intensive fish rearing to reduce size variations and have resulted in differences in growth, production, feed conversion, and foodfish size distribution. Moreover, size grading practices have been advocated method to control large differences in the size of fish during the nursery period of many piscivorous fish species as noted by [31]. Furthermore, [35] notes that sorting enhances feeding since ration sizes and feed granulation can be customized to the fish size. In a study to determine the effects

of size grading on the growth performance and cannibalism of *C. gariepinus* [36] noted that, the growth performance of *C. gariepinus* was affected by the frequency of fish grading whereby the growth rate was improved by 15% and 12% in the grading every two weeks and grading every four weeks over the control group. The study also established that mortality owing to cannibalism was affected by grading frequency where the highest cannibalism mortality occurred in *C. gariepinus* where there was no grading (42.4%) followed by grading every four weeks (18.9%) and intermediate at grading frequency every two weeks (7.5%). Therefore, hatcheries' operators in Kenya have adopted grading techniques to effectively reduce intracohort cannibalism rates in larviculture of *C. gariepinus* as noted by [31] to enhance its seed production.

#### **3.4 Management strategies by the government**

The government has established a system of hatchery authentication to ascertain the quality of broodstock, the seed produced, and the availability of necessary facilities and skills in order to maintain the quality of catfish seed [37]. The authentication of hatcheries is being undertaken by the State Department for Fisheries and the Blue Economy in collaboration with Kenya Marine and Fisheries Research Institute (KMFRI) [37]. Note that the steps followed by the system are not very far from the approach that has been followed by other major aquaculture-producing countries like China. Similarities are observed in how the government responded to seed-quality problems by encouraging investment in hatcheries by the private sector, whereby hatcheries in Kenya are mostly owned by private fish farmers (82%) and only a few (18%) are owned by the government institutions [37]; instituting seed-quality control policy measures to improve seed-quality management; including the establishment of fish-seed certification methods and standards, which were developed by KMFRI in collaboration with the Kenya Bureau of Standards (KEBS) and State Department for Fisheries and the Blue Economy; and encouraging and supporting the production and distribution of quality seed [38].

These management strategies were aimed at maintaining the quality of brood fish and seed because poor management had led to deterioration in the quality of broodstock and seed over time as noted by [37]. Therefore, a training program for hatchery managers was initiated at the National Aquaculture Research Development and Training Center (NARDTC), Sagana in 2009 where all hatchery managers were trained on the necessary skills in hatchery operations. Moreover, [37] reports that, to enable fish farmers purchasing catfish seed from government-endorsed hatcheries trust the product, a seed certification and accreditation system was developed [37]. Also notes that, in Kenya, one of the requirements for a hatchery is that the manager should possess a diploma or degree certificate in aquaculture. This is an effort by the government to make hatchery management more professionalized and able to adopt technologies, innovations, and management practices (TIMPS) leading to higher production of quality catfish seed.

#### **4. Conclusion**

The potential of *C. gariepinus* to make a significant contribution to Kenyan fish production is very real. The demand for seed has increased steadily and several farmers have engaged in the culture of catfish. The techniques, such as artificial propagation, the use of live and dry formulated feeds, and grading have been developed for

*Advances in African Catfish (*Clarias Gariepinus*) Seed-Production Techniques in Kenya DOI: http://dx.doi.org/10.5772/intechopen.105665*

African catfish production and can be easily adopted by fish farmers to enhance the growth and survival of larvae and fingerlings. Certainly, in the next few years, catfish farming will make a significant contribution to food security, foreign exchange generation, and the creation of employment opportunities, which are key to economic growth and poverty alleviation in Kenya.

#### **Conflict of interest**

The author(s) declare that they have no known competing financial or nonfinancial, professional, or personal conflicts that could have appeared to influence the work reported in this paper.

### **Author details**

Jonathan Munguti1 \* and Jacob Odeke Iteba<sup>2</sup>

1 National Aquaculture Research Development and Training Center (NARDTC), Kenya Marine and Fisheries Research Institute (KMFRI), Sagana, Kenya

2 Directorate of Fisheries, Busia County, Busia, Kenya

\*Address all correspondence to: jmunguti2000@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Section 4
