Background

Fish are the most resourceful of animals in terms of reproduction. Impairment of reproduction in captivity can be partial or total (Taranger et al., 2009). However, in some species of fish, the gonads may mature at the same time; while in another fish of the same age the gonad may mature and even produce viable gametes while the other does not (Beirao et al., 2019). In many species, these may tarry after wild fish of the same age have spawned repeatedly. Fish farmers need fry or seed in very large numbers. Recently, with low catch from the wild, there is a need to increase production through aquaculture (Oguntuase and Adebayo, 2014; Naylor et al., 2000). The better the reproductive physiology of fishes is understood, the more chances of success with induced breeding (Ochokwu et al., 2015).

However, Fraser (2008) reported that the challenge is to balance the cost of providing a sufficiently “natural” captive environment against the effectiveness of intervening with hormones. In such a case many species will spawn without synthetic hormones with environmental manipulation A complementary approach, environmental manipulation and more attention to broodstock require diet, water quality, stocking, and holding conditions are combined to enhance the outcome of hormone techniques, which can also yield productively (FAO, 2007). 

Including the development of endocrine gland techniques, interest has recently increased in using environmental optimization to bring cultured fish to spawn (Migaud et al., 2013). Bayne (2017) reported that culture conditions differ from those in the natural environment and are often not optimal for the final stages of sexual development, maturation, and the production of high-quality gametes. Meanwhile, providing optimal conditions for broodstock reproduction can reduce the need for pharmacological intervention. In species such as Clarias gariepinus, where the environmental regulation of sexual development is apprehended, culturists uphold several stocks under environmental regimes that allow sequential spawning throughout the year (Ochokwu et al., 2015). However, more research on the environmental regulation of reproductive development in tropical species like (Clarias) will surely enhance the  development of technologies for all year round seed supply in the Lake Chad region of Northern Nigeria (Gupta et al., 2004).

The demand for catfish fingerlings is very high all over Nigeria but the major problem being experienced by hatchery operators in the dry northern zone of Nigeria is the seasonality in the production of Catfish fingerlings (Miller and Atanda, 2010), the quality of the water, pH, High rate of mortality during the first two weeks after breeding, availability, and accessibility of the broodstocks, viable and matured gametes (Migaud et al., 2013). Catfish are known to spawn/breed naturally during the rainy season both in captivity and in the wild (Akankali et al., 2011). The length of the rainy season in various parts of the country, determines the length of the breeding period in those areas (Cochrane et al., 2009). This breeding habit most adversely affects the northern part of the country where the rainy season is limited to only 4-5 months in a year.

So far there have been few studies on the efficacy and effectiveness of these two hormones in the arid zone (Northern Nigeria). Although capture fisheries activities are predominant around Lake Chad Basin, yet this study shall further enlighten prospective fish culturist, towards catfish fingerling production in a more economical technique and creating possibilities of producing fingerlings throughout the year, by enhancing proper timing in fish seed production in the zone to satisfy the quest of those that have embraced aquaculture. Breeding/fingerling production has been limited to 4-5 months of the rainy season and collection of catfish fingerlings from the wild (open water) has been the source of fingerlings and this has not been adequate in term of quantity for aquaculture production (Ponzoni and Nguyen, 2007), leading to the importation of fingerlings from the southern regions of Nigeria with losses of a large number due to transportation stress. Hence research of this nature shall solve some of the limitations in arid zone aquaculture. More so, Barange et al. (2018) reported that the resultant reduction in the Lake Chad surface water, water depth, and near absence of open water for so long a period might serve as an opportunity for practicing flood plain pond culture reducing the stress of fishermen trekking longer distances before reaching the receding lake water bodies. The Lake Chad basin is a very prominent livestock and agricultural area and most investments in these activities depend on the neighboring countries (Niger, Chad, Nigeria, and Cameroun Republics) (Zieba et al., 2017), this could burst the increase in fish farming, fish demand, and fish marketing activities due to high population and different ethnicity within the region (Zieba et al., 2017). The general objective of this work is to assess the efficacy of ovaprim and pituitary gland extract in the Induced reproduction of Clarias gariepinus fry/fingerlings in the arid zone of northern Nigeria. To evaluate the growth of the F1, and subsequently point out the reason while fish farmers in the zone should use ovaprim/pituitary in fish breeding to meet up with the demand for fish.

1 Materials and Methods

The experiment was done in the Hatchery Unit of Federal College of Freshwater Fisheries Technology (FCFFT), Baga, Borno State, Nigeria. FCFFT is situated in Kukawa Local Government Area of Borno State, which falls within the Lake Chad Basin. Baga lies on latitude 12^o-55’N and longitude 13^o-35’E and has a population of about 105,588 people (Biu et al., 2020). The major occupation of people is farming and fishing. The “Baga” fish trading is known all over the country and forms a great item of international trade between Borno and other States. The dominant ethnic group is Kanuri, however, a sizeable number of Hausa, Fulani, Igbo, Yoruba, and international tribes from Chad, Niger, Cameroon, and other African countries co-exist peacefully by the lake. The peak of the annual rainfall commence in August and ends in October. Average water temperature during peaks of breeding season ranges from 22℃～32℃ and as low as 14℃ in the dry season (November to December) (Sule and Raji, 2003). 

1.1 Collection and acclimatization of experimental fish 

Twenty (20) broodstocks of C. gariepinus average weight for males 1.2 kg and females 800 g in a ratio of 12:8 were collected from fishermen at the landing site of Lake Chad and transported to Federal College of Fresh Water Fisheries Technology, Baga in a plastic trough of 50 cm x 30 cm deep. The physicochemical parameter of the Lake Chad water was: pH-7.0, water temperature 28℃, Dissolve 0xygen 4.00 mg/L. The broodstocks were collected in July 2019 and acclimatized for a month in a 10 m² earthen pond in the FCFFT Hatchery complex. They were fed twice daily at 3% of their biomass with a 40% protein diet. 

1.2 Collection of the pituitary gland

The pituitaries were collected from four (4) males as shown in Figure 1. The head of the fish was turned upside down, a sharp butcher's knife was used to cut the lower jaw away (cranium). The skull was lifted to expose the brain and the blood was cleaned off, showing the fatty lobe substances exposing the olfactory nerves of the brain. The pituitary gland was located on the top of the skull after gently removing the entire brain, it is a pinky white globule-like organ located on the ventral side of the brain. The pituitaries were collected with a pair of tweezers and put in a mortar and crushed, 2 mL of physiological solution was added (9 g of NaCl / 1 liter of distill water) (Shanthanagouda and Khairnar, 2018).

Figure 1 Extraction of pituitary gland

1.3 Hypophysation and induced breeding

The selected females and males were injected intramuscularly with ovaprim and pituitary gland extract in Figure 2. 0.5 mL/kg for ovaprim and 2 mL/kg of pituitary extract. The male received half of what was administered to the females. The injection of the two hormones was done at the same time, after which the injected breeders were kept in an aerated holding plastic tank containing oxygenated water.

Figure 2 Injection of C. gariepinus with ovaprim/pituitary

1.4 Gametes collection 

Hand stripping of females was carried out after the latency period of 10~12 hours respectively. The females were first cleaned with a hand towel to avoid water having contact with the eggs during stripping. Stripping was done by applying pressure on the abdomen as shown in Figure 3, the fecundity was estimated. While for the testes the abdomen was gently dissected using a surgical blade and the testis were located and measured using meter rule for the sperm length, 2 mL syringe was utilized to make an opening on the testis and the milt from each lobe was collected separately and measured Figure 4. The male was stitched as shown in Figure 5 and returned to the spent tank for survival. During this period the stitched males remain for two weeks inside the water without feeding. The healed male was returned into the broodstock tanks and fed. Subsequently, it was ready for reuse after four (4) months respectively (Onyia et al., 2015). 

Figure 3 Egg stripping

Figure 4 Collection of milt from the male broodstock

Figure 5 Stitched male (survived after two weeks)

1.5 Eggs fertilization and incubation

50 eggs from each treatment were placed in a dry Petri dish replicated five times, 0.5 mL of milt was added and allowed for 2 minutes to fertilize and counted under a microscope (mg x40). The fertilization rate was calculated as reported by (Ochokwu et al., 2016).

% Fertilization = Number of fertilized eggs/total number of eggs x 100

% Hatchability = Number of hatchlings/total number of incubated eggs x 100

% Survival = Number of fry /No. of stocked hatchlings x 100

1.6 Incubation of eggs (indoors)

However, 100 fertilized eggs from each treatment were replicated five times and incubated in well-aerated rectangular concrete (indoor) tanks of 1 m x 1 m x 1 m in a complete randomized design arrangement to evaluate for the growth performance and survival. Hatchlings were fed ad-libitum with fish meal. After one week, the pooled weight of fry in each tank was taking using a sensitive balance ACCULAB 333 to the nearest 0.1 g to adjust the feed, the growth in length was measured using meter rule (cm), and survival rate recorded as previously reported by Onyia et al. (2016).

1.7 Fingerling stage (outdoors)

At the end of the feeding trial for four weeks in an indoor facility, 50 fingerlings replicated five times were transferred to the nursery pond (2 x 2 x 1.5 m) in an outdoor pond and reared for four weeks in a complete randomized design setup. Fingerlings were fed with a 40% crude protein diet (coppen feed) trice daily at 5% of their biomass. Initial pooled weight of the fingerlings/treatment were taken while weekly 20 fingerlings of each treatment were taken for length, weight measurements, and survival was recorded for four (4) weeks in the concrete nursery ponds (outdoors). 

1.8 Monitoring of physicochemical parameters

The following physicochemical parameters were monitored throughout the rearing period Temperature, Dissolve Oxygen, pH, and conductivity.

1.9 Statistical analysis

Variations in the data generated from the two hormonal treatments were subjected to one-way analysis of variance (ANOVA). The differences in the means that were significant at 5% were determined using Duncan multiple range tests (DMRT) in an SPSS version 20. While the graphs were plotted using Excel software 2013. 

2 Results

Table 1 revealed the fecundity, percentage fertilization/hatchability and survival of F1 reared for a week. C. gariepinus induced with ovaprim had the highest fecundity (10,500) while pituitary was 7,000. The percentage fertility and hatchability for fish induced with ovaprim were (71.4 and 70) respectively while the fish induced with pituitary gland had fertility (68.1) and hatchability (69). The survival rate after a week was highest in C. gariepinus induced with pituitary 65% and ovaprim had 62%.

Table 1 Mean Fertilization, hatchability and fecundity of C. gariepinus induced with Ovaprim and Pituitary gland Note: Means with a different superscript in the same row are significantly different (P<0.05)

However, Table 2 uncover the sperm volume which was higher in the males induced with pituitary gland 3.2 mL, and also has the highest length of the testes 5.2, meanwhile, the male induced with ovaprim had the highest weight of the testes 6.1 respectively.

Table 2 Mean sperm volume, the weight of the testes, and milt volume of C. gariepinus induced with ovaprim/pituitary gland Note: Means with a different superscript in the same row are significantly different (P<0.05)

Figure 6: represent the weekly mean weight relationship due to the effect of ovaprim and pituitary gland extract on the production of clarias gariepinus fry reared indoors for four (4) weeks. There was no significant difference (P>0.05) in the final weight of fish induced with ovaprim after four weeks (6.22) and pituitary gland (6.82).

Figure 6 Weekly weight (g) of C. gariepinus induced with Ovaprim and Pituitary reared in indoor pond

Figure 7: weekly increase in length of C. gariepinus fry induced with ovaprim/pituitary reared indoor. There was no significant difference across the treatments in length increase of the fish reared indoors. The final length for C. gariepinus hatchlings induced with pituitary was (6.82) and ovaprim (6.22).

Figure 7 Weekly length (cm) of C. gariepinus induced with Ovaprim and Pituitary reared in an indoor pond

Weekly weight (g) of C. gariepinus hatchlings induced with ovaprim/pituitary gland reared in an outdoor pond is presented in Figure 8. The final weight of the fish induced with ovaprim after four weeks was 56.91 g and the pituitary had 56.98 g, interestingly there was no significant difference among the treatments.

Figure 8 Weekly mean weight (g) of C. gariepinus induced with Ovaprim and Pituitary reared in outdoor pond

Figure 9 showed the increase in the length of the hatchlings reared in an outdoor pond. At the end of the four weeks of rearing, fish induced with ovaprim had 24.72 cm while pituitary had 24.69 respectively.

Figure 9 Weekly mean length (cm) of C. gariepinus induced with Ovaprim and Pituitary reared in outdoor pond

Figure 10: delineate the DO of the water used to rear the fry in an indoor pond. The DO recorded was 4.5 mg/L in pond water containing fish induced with pituitary and 4.2 in pond water treated with ovaprim.

Figure 10 Dissolve oxygen level of the water used to rear the fry induced with Ovaprim and Pituitary reared in indoor pond

While in Figure 11. Which represents the pond water used to rear the fingerlings in an outdoor pond. The DO was 3.4 mg/L for the pond treated with pituitary and 3.2 for the ovaprim treated ponds.

Figure 11 Dissolve oxygen level of the water used to rear the fry induced with Ovaprim and Pituitary reared in outdoor pond

Figure 12 shows the pH (7.2), conductivity (610) and Temperature (28^oC) of the fingerlings reared in an indoor pond. There was no significant difference.

Figure 12 Some physicochemical parameters of the water used to rear the fry induced with Ovaprim and Pituitary reared in outdoor pond

Subsequently, in Figure 13. The same trend was observed in the water utilized to rear the fingerlings in an outdoor pond. pH 7.9 in pond treated with pituitary and 8.0 in pond treated with ovaprim, while the conductivity was 460 and temperature 30^oC.

Figure 13 Some physicochemical parameters of the water used to rear the fry induced with Ovaprim and Pituitary reared in outdoor pond

Table 3 displays the growth parameters of the fry reared in an indoor pond. There was no significant difference in the weight gain of the fry treated with pituitary (8.77) gland and ovaprim (8.13) also in mean length gain the fry induced with ovaprim had 6.08 and pituitary 6.7. However, the percentage of survival was higher in pituitary induced C. gariepinus 78% and ovaprim 76%.

Table 3 Growth parameters of fry reared in an indoor pond Note: Means with a different superscript in the same row are significantly different (P<0.05)

Table 4 indicate the growth parameters of the fingerlings reared in an outdoor pond. There were no significant differences in the mean weight gain. Pituitary had 14.42 and ovaprim 14.35 respectively. The survival rate was higher in the fingerlings reared outdoor. Ovaprim had 98% while pituitary was 95% survival.

Table 4 Growth parameters of the fingerlings reared in an outdoor pond Note: Means with a different superscript in the same row are significantly different (P<0.05)

3 Discussion

The result obtained in this research revealed the efficiency and profitability of induced breeding using natural hormone (C. gariepinus pituitary extract) and ovaprim. It exposed that there is no significant difference in using synthetic hormone (ovaprim) and natural hormone (pituitary gland) in inducing catfish breeding. In this research the weight of the broodstock used was males (1200 g) and females (800 g) and all responded positively to the hormones. Subsequently spawned 10 hours after injecting with hormones at 29^oC.

The fecundity rate was higher in the females induced ovaprim than females induced with pituitary extract, this coincides with Chattopadhyay (2018) who recorded an increase in the fecundity of catfish (Ompok pabda) induced with ovaprim, meanwhile, the fish injected with carp pituitary yet had high fecundity as also reported in this research, but do not comply with (Olaniyi and Akinbola, 2013) who reported an increase in fecundity of fish induced with the pituitary gland. However, Ganias (2018) defined fecundity as a measure of gamete produced which reveal the number of matured eggs released in a breeding period while Bradshaw and McMahon (2008)reported that fecundity is the physiological maximum potential reproductive output of a female fish within its lifetime and in totality typify one of the major fundamentals of theoretical and applied population biology.

Towers (2014) reported that the temperature, pH, and season of the year could be a causative factor to increase or low in fecundity. Moreover, fish size and weight, egg diameter, the viability of the eggs, latency period, and amount of toxin in the culture medium/water are inclusive.

The percentage of fertilization and hatchability recorded in this research were higher in the fish induced with ovaprim. However, both treatments gave a high result to that effect. This agreed with (Hamid et al., 2005; Ndimele and Owodeinde, 2012; Olaniyi and Akinbola, 2013; Chattopadhyay, 2018); also Das et al. (2016) and Hossain et al. (2012) conveyed high fertility in fish induced with ovaprim but Hossain et al. (2012) also report high hatchability among the females induced with pituitary extract. Subsequently, the fish induced with pituitary extract recorded high survival (65%) after four weeks of rearing in an indoor pond against the fish induced with ovaprim (62%), this concurs with (Chattopadhyay, 2018).

The growth rate of the hatchlings induced with pituitary and ovaprim reared indoors and outdoor revealed that there was no significant difference (P<0.05) across the treatments. Ndimele and Owodeinde (2012) recorded poor growth rate across the treatments when compared with this research, moreover, the highest weight gain (8.88 g) observed in Ndimele and Owodeinde (2012) was in ovaprim induced fish reared for 56 days which was lower than the weight gain obtained in this research (14.35 g). The same trend was observed in Abdul et al. (2017), who recorded poor growth after feeding the fry for 28 days. Similarly, Ikechukwu et al. (2019) recorded an increase in weight of the fish induced with ovaprim and pituitary, He also stated that the fish induced with ovaprim had significant growth which did not differ from those induced with the pituitary. This has proved that the pituitary gland is an alternative for ovaprim which is costly, not easily accessible in the arid zone. The major causes of poor growth in fish farming are correlated with diet (feed, nutrients contents of the feed the fish consumed), the stocking rate, pH of the water, dissolved oxygen (Ochokwu et al., 2019). Another causative effect is the genetic makeup of the parent stock which is inherited by the offspring (Ochokwu et al., 2015). These traits have higher effects on the first generations. 

Similarly, the percentage survival recorded in this work was high in both treatments and it concurs with Ikechukwu et al. (2019) but disagreed with Ndimele and Owodeinde (2012) who recorded poor survival at the end of the research.

4 Conclusion

The research points out the essentiality of using the pituitary gland from available C. gariepinus in the arid zone for breeding and effectively rearing the hatchlings for fingerlings availability in the zone. Both the synthetic hormone (ovaprim) and natural hormone (Pituitary extract from C. gariepinus) positively influenced the reproductive performance of the fish, it exerted positive change in fertility, hatchability growth in weight, length, and survival of the hatchlings both in an indoor and outdoor rearing facility. Finally, the farmers who depend on capture fisheries for survival because of the poor access to synthetic hormone and the cost of purchasing it can adopt the pituitary gland for inducing breeding in the zone. However, in this research 2 mL/kg was used to inject the females and 1ml/kg was injected into the male, this can still change and should not be limited to only 2 mL/kg. The farmers should also be alert throughout the latency period to avoid under or over-ripening of the eggs after injection.

Authors’ contributions

The research was divided into different phases in which the three authors listed, effectively contributed and positively to the completion of the research article. Ochokwu, I.J. Y.Y., Saidu, K.A, Technologist X.X., Prof. Bichi, A.H, Z.Z, Paul, M.M, XX conceptualization, X.X. and Y.Y.; methodology, Y.Y. and Z.Z; software, Y.Y. and X.X; validation, X.X., Y.Y. and Z.Z.; formal analysis, X.X. and Y.Y; investigation, X.X. Y.Y and Z.Z; resources, X.X. and Z.Z; data curation, X.X. and Y.Y; writing—original draft preparation, X.X. and Y.Y; writing—review and editing, X.X. and Y.Y and Z.Z; visualization, X.X.; supervision, X.X. and Y.Y; project administration, X.X.; funding acquisition, X.X. and Y.Y. All authors read and approved the final manuscript.

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