Catfish can be found all over the globe. They mostly bottom feeders that are found in the freshwater region. Other characteristics is such as flattened broad heads and the long whiskers like barbels that protrude from the mouth of the opening (A-Z animals, 2008).
The order for catfish is Siluriformes which comprises of almost 3000 knowns species (A-Z animals, 2008). Almost all catfishes are omnivores, however others have highly specialized diets such as wood-eating loricariids (Nelson et al., 1999) and while there are also parasitic catfishes that can feed by the blood of other organism such as fish (de Pinna, 1992; Spotte, 2002). The barbels is used to taste the foods as it have taste buds. In addition, barbels are also used to hunt as the barbels can detect the smell of the prey and food in the However, some catfish lacks the prominent barbels (A-Z animals, 2008).
Catfish are additionally ready to guard themselves as some are furnished with resistance mechanism. Illustrations resemble sharp balance spines. It can perpetrate serious harm to predators (Baron et al., 1996). Some catfish can be venomous (Dorooshi, 2012). They are different from most freshwater fishes as they are nocturnal and depend a lot on senses other than sight, such as tactile and chemo sensitive barbels, or a bigger olfactory organs. Thus, the catfishes are able to adapt their lives in different habitats such as caves, aquifers, and deep river channels. Meanwhile, others can regularly leave the water and move to land such as the air-breathing clariid catfishes (Burgess, 1989).
Their average size is around a meter in length normally somewhat less relying upon the species (A-Z animals, 2008). In any case it can go in estimate from only a centimeter long to more than two meters in length. The biggest species of catfish is European wels catfish, 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 nearly 3 meters in length.
2.2 Japanese catfish
The morphology of the Japanese catfish is the regular 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 have barbels as any common catfish. The specialty of the Japanese catfish is having one pair mandibular barbell which is longer than the head while another pair of mandibular barbell is 1/5 to 1/3 of the length of the maxillary barbell (Liu, 1990). Amid adolescent stage, this fish is around 6-7 cm for standard length. Also, amid this stage, they really have one additional combine of mandibular barbell however it deteriorates as it enters the adulthood (Atoda, 1935).
The Japanese catfish can make its home in or under stream or lake banks, depressed logs, shakes or even rocks. While others would discover openings in banks, and others make the gaps themselves. The spawning season is in the spring or late-spring from May to June. They are able to spawn eggs around 5,000 to 10,000 eggs depending on their age and size. While for sex, the apparent sex ratio of the species is extremely high toward females. Intraspecific variety in their regenerative nature, especially mating conduct, has been seen inside neighbourhood populaces in Japan (Maehata, 2007).
In Japan, a past investigation of Japanese catfish in various lake indicates diverse mating conduct. For instance the Biwa lake populace demonstrates a settled succession of activities, for example, pursuing, sticking, enclosing with pressing by the male, and hovering of the matched fish, and females are constantly enveloped by a solitary male (Maehata, 2002), while at the Ooi lake and Fuefuki lake populations does not demonstrate such the same behavioural sequence which was the process of enfolding a female’s body by a male. Circling by the paired fish has not been seen but instead the females are usually enfolded by two males (Maehata, 2007). During spawning Japanese catfish will scatter their eggs, which believed to be aimed at reducing juvenile mortality (Katano et al., 1988). The male is usually the main caretaker and defender of the eggs.
As the fry continue to grow, their diet will begin increases as many type of animals such as crustaceans, clams and small fish become their prey (Katano et al., 1988). Almost all the matured adult fish are active and feed at night however they also feed in condition such as cloudy and also in muddy waters during the day time. Theirs hunting technique rely upon their sense of smell and taste due to having poor vision (Maehata, 2007). As their larvae had aged to juvenile and become matured, they will then move in schools. They do not have migrating behaviour such as travelling downstream and upstream river. But will spend a lot of their lives in lakes, reservoirs and rivers.
2.3 African catfish
The African catfish is a prevailing freshwater fish. It can develop to in the vicinity of 1.4 and 2m long and can weigh from 8kgs to 59kgs (Freyhof, 2016). Its body colouration 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). Underparts are pale olive to white and are mottled unpredictably with dull tanish green, or consistently gleaming olive.
It is heavy boned with a level headed fish with premaxilla and having lower jaw pointed teeth organised in few lines and has four pairs of long trailing sensory organs known as barbels around its mouth (A-Z animals, 2008). It 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 insatiable predator and eat almost everything (Ataguba et al., 2012). Their prey includes insects, crabs, plankton, snails, fish, young 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 move in groups at the water surface. While it additionally shows an assortment of encouraging behaviour including sucking the surface for earthbound creepy crawlies and plant pieces washed into the water by overwhelming rains and pack-hunting of small cichlids. The growth is generally rapid, which can obtain maximum size within a couple of years (FAO, 2008).
African catfish are generally conveyed far and wide. The species extend from South Africa up to Middle, West and North Africa. It likewise dispersed around Middle East and Eastern Europe. They are additionally similarly introduce in Jordan, Lebanon, Israel and Turkey. It has likewise been brought into most different nations in Africa, and also a few in Europe, Asia and South America. Similarly to other species, China introduced it within its rice-fields and is currently among the main producing countries (De Silva, 2010). The pattern for African catfish has increased throughout the years as one of the biggest fish species in aquaculture. The market for African catfish in the sub-Saharan Africa is increasing and evolving each year (FAO, 2010).
2.4 Aquaculture production of catfish
By and large, all catfishes around the world affect the economy as they have esteem and are gathered as human utilization, pet exchanging and recreations. The overall catch creation of freshwater and marine catfishes in 2000 has surpassed 500,000 metric tons (FAO, 2000). A few catfishes, for example, the flathead catfish in North America and the Goliath catfishes in South America are forcefully looked for angler in the angling sport (FAO, 2000). In contrary, numerous catfish has been translocated and acquaint with new zones which makes some generous monetary misfortune and 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 also the flathead catfish, Pylodictis olivaris, in Atlantic slope drainages (Fuller et al., 1999).
In Asia and the Pacific, the family Clariidae (Clarias spp.) had dominated the production, by being up to 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. While the African catfish is the only introduced species that had a significant effect on the Asian aquaculture industry (FAO, 2010). The first introduction was done in the year of 1975 located in Vietnam, where the species was then spread widely all over Asia. Although Asians do not find its meat quality and its large size preferable, its rapid growth and hardiness has made it interested among the fish farmers. While for Japanese catfish, it is rapidly gaining popularity in aquaculture industries mostly in Asian region. It has been used cultured in Japan by many aqua culturist. In Vietnam, the production is very high in middle and lower section of rivers where they are harvested throughout year. Japanese catfish is also a sport fish. Notably, fisherman love catfish as one of the fishing game in the world.
2.5 Growth performance of catfish
The development of a fish can be characterized as an adjustment in magnitude,it can be estimated in size and tissue piece and speaks to a standout amongst the most noteworthy parameters in aquaculture (Silva et al., 2015). Growth is estimated in units of length and weight and is best spoken to as the particular development rate. The relationship between weight and length provides an index of the state of well-being of a fish (condition factor ‘K’Fishes display a ‘determinate’ sort of development in brief types of hotter areas and a ‘indeterminate’ sort in extensive types of colder districts (Dutta, 1994). It could also be measured by using certain 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 number of environmental factors, such as the temperature, the oxygen concentration, the salinity and the photoperiod, can also become the influence 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 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) indicated that both high and low densities had detrimental effects on fish welfare based on juvenile African catfish of 10-100g. Factors such as feed affects the growth of African catfish by the protein level contain in the feed. High level of protein is essential to the growth of fish but optimum level is to be 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 growth (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.