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

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.

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].

Figure 1.

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

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 2.

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

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 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].

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 high-quality 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 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 non-financial, professional, or personal conflicts that could have appeared to influence the work reported in this paper.