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Culture Pond Influences the Growth and Survival of Clarias gariepinus Fingerlings reared in Poly and Monoculture

Monoculture is the rearing of single species of fish in a pond while polyculture is the farming of two or more species in the same physical space. This study aims to compare the growth parameters of Clarias gariepinus fingerlings in monoculture and polyculture, using concrete and earthen ponds in a randomized complete block design. The polyculture, comprised of Clarias gariepinus and Oreochromis niloticus. 480 fingerlings were used; the stocking density was 40fish in a 3x2x1.5m depth with initial weight (4.84±0.11547) for C. gariepinus in monoculture and 40 each in polyculture with an initial pooled weight of O. niloticus (50g) replicated thrice, it was fed for eight weeks with commercial feed (40% crude protein). Weekly, random sampling was done to measure the growth and adjust the feeding rate. The results revealed that polyculture has the best mean final weight (160.07±0.18559g) and weight gain of 155.29, while the highest total length (45.666±3.179) was recorded in monoculture for Clarias gariepinus reared in an earthen pond. The polyculture had the highest specific growth rate (2.46), Relative growth rate (246.49), and condition factor (0.184). There was a significant difference (P<0.05) in monoculture of both concrete and earthen ponds. Original Research Article Onyia et al.; AJFAR, 14(4): 22-28, 2021; Article no.AJFAR.73378 23


INTRODUCTION
Monoculture is the rearing of single species of fish in a pond or tank, the culture of Clarias gariepinus only or Oreochromis niloticus [1]. The culture endows the farmer to formulate feed that will meet the nutrients requirements of a specific fish, particularly in the intensive and semiintensive culture system [2]. Fish of diverse ages can be stocked such as omnivores and herbivores species, this can enhance selective harvesting [3]. Polyculture is the production of two or more cultured species either two different fish species or fish with animals or crops in the same physical space within the same period. The major objective of polyculture is to produce multiple products that have economic value [4]. In a polyculture system, fish farming is fundamentally distinguished according to their level of intensification; however, this is significantly defined according to their feeding practices. However, Aquaculture is the raising of animals and plants in a controlled and semicontrolled environment, in an Aquaculture system, feed typifies more than 50% of the total operating cost [5]. Similarly, other production cost includes water, land, capital, labor and the fish seed. Polyculture can be carried out intensively, semi-intensive and, in extensive methods [6].
In Nigeria, African catfish; C. gariepinus, C. anguillaris, Heterobranchus bidorsalis, H. longifilis and, their hybrids are the most cultured and consumed because of their hardiness, rapid growth, stress resistance, adaptation ability in captivity and can utilize both natural and artificial feed for growth and body maintenance [7]. In Nigeria, overfishing has led to the extinction of most wild species, due to high demand by a local market. In addition, the growing population has motivated the fishers to fish more; hence this has necessitated farmers into engaging in aquaculture systems with little or no knowledge; since that is the only way they can survive and feed their family in a population of over 200 million people.
Aquaculture is in a stage of development [8], most of the farmers engaging in aquaculture have little or no knowledge of the aquaculture management practices and feeding methods. The majority of the fish farmers' in Nigeria utilize concrete ponds, plastic tanks, fiber tanks and, tarpaulin ponds, which are not economical, and are not used for long-term farming because of the impact of the sun. Researchers have worked on survival rates in polyculture of catfish and Tilapia, [8][9] examined the impact of stocking density on C. gariepinus and O. niloticus; while [10] ascertained the performance of C. gariepinus, O. niloticus under integrated farming with Broiler. However, [11] reported the effect of prey density, predator size, and feed supplementation on the polyculture of C. gariepinus and O. niloticus. But in this research, the growth parameters of C. gariepinus reared in an earthen pond and concrete pond have not gained attention. In this research, the influence of concrete pond and earthen pond on the growth performance of C. gariepinus reared in a monoculture and polyculture system were evaluated. The aim was to expose its significance to fish farmers, to encourage them to practice polyculture and utilizing earthen ponds to maximize production and economically increase yield.

MATERIALS AND METHODS
The Experiment took place from 25 th March 2019 to 20 th July 2019 at the Department of Fisheries Teaching and research farm, Modibbo Adama University of Technology, Yola, Adamawa State. The state is located on latitude 9.20-9.33ºN, longitude 12.30-12.50ºE and, an altitude of 185.9m. Yola has an average annual rainfall of about 759mm, with a maximum temperature of 39.7ºC. The rainy season commences in May and ends in October. The dry season commences in November and ends in April [12].

Experimental Fish
A total of 480 fingerlings; 360 C. gariepinus and 120 Oreochromis niloticus were utilized. The fingerlings were collected from the nursery pond in the research farm. Polyculture consisting of 40 Oreochromis niloticus of 50g pooled weight was stocked before the commencement of the research. One month later, 40 C. gariepinus (4.8g initial body weight) was introduced in the earthen pond consisting of O. niloticus while in the monoculture, 40 C. gariepinus were stocked in an earthen pond and another 40 C. gariepinus in a concrete tank all in an outdoor facility and replicated thrice. All the ponds (concrete and earthen pond) were replicated thrice was 3x2x1.5m depth. None of the ponds were fertilized with any organic/inorganic manure before the commencement of the feeding trials. All the fishes were fed with prime crown twice a day at 5% body weight. Fish were weighed weekly to ascertain the weight and length increase and subsequently adjust the feeding rate. Also, the water quality parameters (pH, dissolved Oxygen, Temperature) were monitored throughout the experimental period.

Experimental design
The research consists of three treatments with three replications each using a randomized complete block design (RCBD) as shown below: Treatment 1 (monoculture) concrete tank stocked with forty (40) C. gariepinus only Treatment 2 (monoculture) earthen pond stocked with forty (40) C. gariepinus only and Treatment 3 (polyculture) earthen pond stocked with forty (40) C. gariepinus and forty (40) Oreochromis niloticus, all the treatments were replicated three times for accuracy.
The ponds are 3x2x1.5m in depth

Ponds preparation
The earthen ponds were drained, allowed to dry for one week to lay off every aquatic organism in the pond, and cored to avoid leakage. While the concrete tanks were washed and sanitized with saline solution before the commencement of the experiment. The water was pumped into the ponds two days before the experiment commenced. The same volume of water was maintained throughout the experimental period.

Statistical analysis
Data collected were subjected to one-way analysis of variance (ANOVA) using SPSS 20, differences between the means were analyzed using Duncan multiple range tests (DMRT).

Weekly Growth in Weight of Monoculture and Polyculture of C. gariepinus Fingerlings
The result of the growth in weight of monoculture and polyculture of C. gariepinus fingerlings reared in concrete and the earthen pond are presented in Table 1. C. gariepinus in polyculture had the highest final weight after the feeding trial 160.07±0.18559g followed by monoculture in earthen pond 148.04±0.11547g and the least was in monoculture in concrete pond 92.04±0.11547g.

Weekly growth in the length of monoculture and polyculture of C. gariepinus fingerlings
The result of the weekly growth in length of monoculture and polyculture of C. gariepinus juvenile reared in concrete and the earthen pond are presented in  Table 3 displayed the result of the Growth parameters in polyculture and monoculture of Clarias gariepinus in concrete and earthen ponds. The C. gariepinus reared in polyculture in an earthen pond for 56days had the highest weight gain 155.29g, it was followed by C. gariepinus reared in monoculture (earthen pond) 143.22g and the least was in C. gariepinus reared in a concrete pond 87.0g. However, the C. gariepinus reared in a monoculture in an earthen pond had the highest length gain 40.33cm, followed by C. gariepinus reared in polyculture in an earthen pond 39.00cm and the least was in C. gariepinus reared in a concrete pond 33.33cm. The specific growth rate ranged from 1.38 in C. gariepinus reared in a concrete pond to 2.27 in an earthen pond (monoculture) and 2.46 in polyculture. The relative growth rate was 138.4 in a concrete pond, 227.33 in monoculture (earthen pond), and 246.49 in polyculture. The percentage survival in all the treatments was 100%, and there was no significant difference (P<0.05) in the condition factor across the treatments. Means with different superscripts are significantly different (p<0.05)

Water quality parameters
The water quality parameters are presented in table 4. The temperature ranged from 32 0 C in the concrete pond to 33 0 C in monoculture and polyculture reared in an earthen pond. Dissolve Oxygen ranged from 1.62mg/l in a concrete pond, 2.21mg/l in monoculture in an earthen pond, and 2.28 in the earthen pond (polyculture), the pH (6.5) in a concrete pond, 7.2 in an earthen pond (monoculture), and 7.8 in polyculture. Ammonia was 0.15 in a concrete pond, 0.34 in monoculture in an earthen pond, and 0.39 in the polyculture respectively.

DISCUSSION
The weight increase of C. gariepinus in this research has proved that irrespective of the essentiality in the quality of feed consumed; other parameters are relevant in weight and length increase in farm animals; the culture medium, stocking density, size of the pond, physicochemical parameters of the water, general cleanliness and hygiene and level of exposure to toxic substances is weighty. The rearing process involved concrete ponds and earthen ponds; the C. gariepinus reared in the same pond with O. niloticus (polyculture, without fertilization) inherently increased in the body weight. The rate of the growth was incredible when compared with other treatments; this accord with previous research [14] who reported higher weight gain in C. gariepinus reared with common carp and Tilapia; subsequently, previously [15] reported a higher growth rate in pangasius catfish reared with silver carp, while [16] had a higher growth rate in polyculture of Clarias gariepinus and Oreochromis. Similarly, [9] recorded an increase in weight gain when C. gariepinus and O. niloticus were stocked in ratio 1:3 than in ratio 1:1 and 1:2; also the same trend was observed in previous research [17] respectively. There was a significant difference (P<0.05) across the treatments in the mean weight gain. In Nigeria, majority of the fish farmers utilize concrete pond and plastic tanks, with an increase in growth [18,19], while some reported low growth with high mortality at the early stage of rearing [20], meanwhile, the mortality rate can be attributed to low pH of the water [12]. However, this research has proved that the rearing of catfish (C. gariepinus) in an earthen pond is more economical, effective and gives a better growth rate and yield when compared with C. gariepinus reared in a concrete pond. The weight gain recorded in monoculture of C. gariepinus reared in a concrete pond was 87.02g; however, the monoculture of C. gariepinus reared in an earthen pond was 143.22g while polyculture had 155.29g.
Concerning the growth in length, C. gariepinus reared in monoculture (earthen pond) had the highest growth in length, this is in comport with Khan et al. [15]; similarly, Algrient et al. [21] reported the highest length gain in monoculture C. gariepinus.
There was a significant difference (P<0.05) in the result of the specific growth rate, relative growth rate and, condition factor across the treatments. C. gariepinus reared in the polyculture system had the highest in the above-mentioned parameters; it agreed with researchers [9,[14][15]. There was no mortality at the end of the research across the treatments.
The water quality parameters carried out during the research revealed that the ponds were in good condition. However, the earthen ponds showed an increase in pH of the water; this disagreed with [22] who reported a decrease in pH of the pond water with the addition of catfish. The temperature was high. Subsequently, the dissolved Oxygen, turbidity observed in the research concord with [23]. Hence across the treatments used in this research, Polyculture has proved to be effective and productive. Rearing of C. gariepinus and O. niloticus maximized the growth of C. gariepinus which will result in higher productivity, the income level of the farmer, net profit per unit area of a pond used, and maximize feed intake.

CONCLUSION
The research revealed that the use of an earthen pond as a rearing medium in C. gariepinus in a polyculture system is advantageous, productive and, economical. It is a means of increasing the weight of the fish. This has established the reasons for Nigerian farmers to effectively utilize the vast land in the country for the polyculture system to meet the high demand for fish for the growing population.

COMPETING INTERESTS
Authors have declared that no competing interests exist.