The catfish can be located around the globe. They are mostly bottom feeders which can be search in freshwater region. Meanwhile, they also have characteristics such as flat broad heads and obtain filament which are called as barbels which are elongate at the entrance of its lip (A-Z animals, 2008).
The known order for the catfish is called Siluriformes which ranges of almost 3000 knowns species around the world (A-Z animals, 2008). In general, almost all catfishes are omnivores, however others have favourite diets such as wood eating locariids (Nelson et al., 1999) and meanwhile there can also exists such as the parasitic catfishes that can feed on the blood of other animals such as the fish (de Pinna, 1992; Spotte, 2002). Their barbels was used to taste the foods as it contains taste buds. In addition, it is also used to hunt as it can help detect the scent of their prey and food in the wild. However, there are catfish that lacks the mechanism (A-Z animals, 2008).
The catfish are prepared to defend themselves as some are furnished with defences’ mechanism. Their defences can resemble as sharp balances spines. It can perpetrate serious damage to enemies (Baron et al., 1996). Other catfish can be venomous (Dorooshi, 2012). They are different from most freshwater fishes as they are nocturnal creatures and usually depend highly on senses other than their sights, such as the tactual and the chemo sensitive barbels, or a bigger olfactory organ. Thus, these creatures are able to adapt their lives in different habitats such as holes, aquifers, and deep river channels. Meanwhile, they also can normally leave the river and walk on land such as the air breathing clariid catfishes (Burgess, 1989).
The general size is around a meter and this normally depend upon the species (A-Z animals, 2008). In any case it can go in estimation from only a centimeter long to more than two meters in length. The biggest species is the European wels catfish, as it can found up to 5 meters long and can weigh around 330 kg (Treeoflife, 2003). Meanwhile, the second largest is the Mekong catfish, which is found living in different parts of the Mekong River that streams through Laos, Thailand, Cambodia and Vietnam. The largest Mekong catfish ever discovered was measured almost 3 meter in length.
2.2 Japanese catfish
The characteristic of the Japanese catfish is the normal for any Silurus species. It has a small dorsal fin which is dark grey at its sides. Their stomach is white colour with sporadic white dabs at each side. They also obtain barbels as any common catfish. However, the specialty of the Japanese catfish is having one pair of the mandibular barbell which is longer than their head while another pair of the mandibular barbell is 1/3 to 1/5 of the total length of their maxillary barbell (Liu, 1990). During the adolescent stage, this fish is around 6-7 cm as their standard length. Also, amid this stage, they have one additional combine of mandibular barbell however it will deteriorates as it enters the adulthood (Atoda, 1935).
The Japanese catfish can create its home in or under of stream or at lake banks, depressed logs, shakes or even rocks. While others would discover openings in banks, and others make the gaps themselves. The spawning season will come in the spring or late-spring from May to June. They are able to spawn eggs around 5000 up to 10000 eggs which depends on their age and size. While for their sex, it can be seen an apparent sex ratio of the species is extremely high toward females to males. They are intraspecific variety in their regenerative nature, especially during mating conduct, as it has been research inside the neighbourhood populaces in Japan (Maehata, 2007).
In Japan, a past investigation of the Japanese catfish in almost various lake has indicates a diverse mating conduct. For instances, in the lake Biwa populaces it had demonstrated a settled succession of activities, for example the pursuing, the sticking, the enclosing with pressing by the male, and by hovering of the matched fish, and the females are constantly enveloped by a solitary male (Maehata, 2002), while at the Ooi lake and at the Fuefuki lake, the populations does not demonstrate such the same behavioural sequence which was the process of enfolding a female’s body by a male. The circling by the paired fish has also not been seen but instead the females will usually enfolded by around two different males (Maehata, 2007). In the spawning activities, the Japanese catfish will scatter their eggs. This was believed to be aimed at reducing the number of juvenile mortality rate (Katano et al., 1988). The male is generally the all-time caretaker and defender of the eggs.
As the fry will continue to grow to adult phase, their diet will begin to increases as many type of animals such as the crustaceans, the clams and also small fish become their food (Katano et al., 1988). In almost all the matured adult fish are active and feed during night time. However, this fish also feed in condition such as cloudy and also in opaque waters during sunlight is available. The hunting method relies upon their sense of scent and taste due to the catfish having very poor sight (Maehata, 2007). When the larvae had aged to juvenile and become matured, they will then began to form schools and move together. Moreover, they do not possess any migrating characteristic such as travelling downstream and upstream river. But will spend a lot of their lives in lakes bottom, the reservoirs and river streams.
2.3 African catfish
The African catfish is a prevailing freshwater fish. It can develop to in the range from 1.4 up to 2m long and can also weigh in from a minimum of 8kgs up to 59kgs (Freyhof, 2016). For its characteristic, the body colouration can fluctuates from olive green, to darker and dark with the flanks frequently uniform dim to olive-yellow with dim slate or greenish darker back (FAO, 2012). In its underparts, the colours are pale olive to white and are mottled unpredictably with dull tanish green, or consistently gleaming olive.
It is heavy bone with a level headed and obtaining premaxilla while having lower jaw pointed teeth organised in few lines. Meanwhile, it also has four pairs of long trailing sensory organs known as barbels around its mouth (A-Z animals, 2008). In addition, the catfish has a high number of gill rakers differing from 24 to 110. The number will increase with the size of the fish. These fish are an insatiable predator and will likely eat almost everything in its sight (Ataguba et al., 2012). Their prey also includes several organism such as the insects, the crabs, the plankton, the snails, small fish, small birds, and many more (Ibrahem, 2011). It is generally an individual bottom feeder, however they are known to be to a great degree versatile to conditions and can move in groups at the water surface. Meanwhile, it can additionally shows an assortment of strongly behaviour such as sucking the surface for earthbound creepy crawlies and also some plant pieces that was washed into the water by overwhelming rains and pack-hunting of small cichlids. The growth is generally rapid, where the fish can obtain their maximum size within a couple of years (FAO, 2008).
African catfish are generally conveyed far and wide around the world. The species can extend from South Africa up to Middle, West and North Africa. It is likewise had been dispersed around different continent such as the Middle East and Eastern Europe. Furthermore, they are also additionally similarly introduce in Jordan, Lebanon, Israel and Turkey. It has also been brought into most of the different nations in Africa, and also a few in Europe, Asia and South America. Similarly to some other species, China also introduced it within its rice fields and is currently holding the position of among the main producing countries (De Silva, 2010). The pattern for African catfish culture has been increase throughout the following years since it introduction as one of the biggest fish species in aquaculture. Even in the market for African catfish in the sub-Saharan Africa has been increasing and evolving each year (FAO, 2010).
2.4 Aquaculture production of catfish
By and large, all of the catfishes around the globe has affected the global economy as they have esteem and are always gathered as human utilization, pet exchanging and recreations. The overall catch record of the freshwater and marine catfishes in 2000 has already surpassed 500,000 metric tons (FAO, 2000). In addition, a few catfishes such as the Flathead catfish in North America and also the Goliath catfish in South America are being forcefully looked for angler in the angling sport (FAO, 2000). In contrary, a numerous number of catfish has been translocated and acquaint with the new zones which makes some of the generous monetary misfortune and could also harm common environments and local fish abundancy (Schmitt, 2016). There is significant catfish pests in North America which is the walking catfish, C. batrachus, in Florida, and while also the Flathead catfish, Pylodictis olivaris, in the Atlantic slope drainages (Fuller et al., 1999).
While in Asia and the Pacific, the family Clariidae (Clarias spp.) had dominated the aquaculture production, by being up to the 80% of the total 76,000 tons catfish which produced in 1991 (FAO, 2000). The most cultured species were C. batrachus, C. macro-cephalus and C. gariepinus. However, only the African catfish was the introduced species that had an important effect on the Asian aquaculture industry (FAO, 2010). The very first introduction was done in Vietnam of the year 1975, where the species was then spread widely all over Asian region. Although the Asians do not find its meat quality and its large size preferable, due to its rapid growth and hardiness of the fish, it has made it very interesting among the fish farming business. While for the Japanese catfish, In general, it is rapidly gaining high popularity in aquaculture industries mostly in Asian region. It has been used cultured in Japan by many aqua culturist. In Vietnam, the production of Japanese catfish is very high in middle and lower section of rivers where they are harvested throughout year. Furthermore, the Japanese catfish is also a known sport fish due to its aggressiveness and powerful body. Generally, fish sport person love catfish as one of the best freshwater fishing game in the world.
2.5 Growth performance of catfish
The development of a fish can be characterized as an increased in magnitude, it can also be estimated by their size and also the tissue piece. It speaks to a standout amongst the most noteworthy parameters in aquaculture (Silva et al., 2015). Growth is estimated by the units of the length and the weight and is best spoken to as the important development rate. The main relationship between the weight and the length can provides an index of the state of well-being of a fish. The condition factor ‘K’Fishes can display a ‘determinate’ which is a sort of development in brief types of hotter areas and an ‘indeterminate’ sort of extensive types of colder districts (Dutta, 1994). It could also be measured by using other criteria such as the glycine uptake by scales, the hepatosomatic index, the RNA:DNA ratio and also the protein retention in the tissues. The nutrition which includes the quality and quantity of food, will play an important role in growth regulation (Siddiqui, 2014).
A few number of environmental factors, such as the temperature, the oxygen concentration, the salinity and the photoperiod, can also affect the rate of growth (Tang et al., 2008). There are fish that can exhibit a determinate type of growth in short-lived species of warmer regions and an indeterminate type in long-lived species of colder regions (Dutta, 1994). The water temperature is a standout amongst the most critical physical variables influencing fish development and creation. Fish are cold blooded creatures which expect around an indistinguishable temperature from their environment (Viadero, 2005).
The growth performance of the African catfish can be affected by many factors such as stocking density, feed formulation and water quality. Past studies of Micha (1976) suggest that the growth of African catfish to decrease with increasing stocking densities. However, (Van de Nieuwegiessen et al., 2008) had indicated that both the high and low densities had some detrimental effects on fish welfare based on juvenile African catfish of 10-100g. Factors such as feed can affects the growth of African catfish by the number of protein level contain in the feed. High level of protein is very essential to the growth of fish but an optimum level is known to ensure high growth efficiency (Tunde et al., 2016).
As for Japanese catfish, the growth of the catfish was very fast and it can grew to an average body weight, 100g at 80 days after hatching in the natural condition (Akazaki et al., 1991). The Japanese catfish has less information regarding nutrients that can help its growth but past studies of Cong Liu (2012) states that the dietary protein of 43% and dietary lipid of7% had no significant growth on Japanese catfish compared to S. meridionalis which had shown better growth performance in the same dietary nutrient. However, the Japanese catfish optimum level of dietary protein is 45% for maximum development (Kim et al., 2014). Sex of the Japanese catfish also influences its growth performance as female grow much faster than male (Kim et al., 2001). This is due to reaching sexual maturity has reduce its growth rate and reduce its feed efficiency for male.