Induced breeding of climbing perch Anabas testudineus using OVASPEC hormone

Climbing perch, Anabas testudineus, is one of the important freshwater fish species distributed in Asia, mostly in Bangladesh, India, Malaysia, Thailand, Vietnam, and Indonesia (Muchlisin and Siti-Azizah, 2009; Hossain et al., 2015; Khatun et al., 2019). This fish has a high commercial value and consumer preference and is favored by the local people because it has good taste and nutritive values (Suriansyah et al., 2011; Akbar, 2012; Muchlisin, 2013). They inhabit in swamps, small rivers, creeks, irrigation canals, and rice fields (Dekar et al., 2018; Nur et al., 2019) and can tolerate estuary conditions and salinities up to 10.2 ppt (Chotipuntu and Avakul, 2010). In Indonesia, the climbing perch is widely distributed in Kalimantan, Java, Sulawesi, and Sumatra, including Aceh province (Bungas et al., 2013; Muchlisin et al., 2015). In the local language of Acehnese, this fish is known as kruep (Muchlisin and Siti-Azizah, 2009). Climbing perch farming has been initiated by several fish farmers. However, this business is still facing obstacles, including the scarcity of high-quality larvae, due to underdeveloped hatchery technology for this fish. Therefore, intensive efforts are crucially needed to overcome this problem.

Hormone manipulation is frequently applied in hatcheries to stimulate gonadal maturation and ovulation in fish (Santika, 201). There are several synthetic hormones available in the market and are often used for fish breeding and seed production, for instance, Ovaprim, Oodev, HCG, Spawnprim, and Oxytocin (Muchlisin et al., 2014; Saptono et al., 2018; Rahmi et al., 2020; Darliansyah et al., 2017; Siregar et al., 2018; Leonita et al., 2021). The application of the synthetic hormones for induced breeding of climbing perch has been reported by several researchers. Saptono et al. (2018) reported that Ovaprim at a dose of 0.5 ml kg⁻¹ body weight (BW) was the best dosage for climbing perch; Siregar et al. (2018) reported that 0.5 ml kg⁻¹ BW was the best dosage for HCG, and Rahmi et al. (2020) tested Oodev hormone and reported that 0.7 ml kg⁻¹ BW was the best dose for this species. In addition, Aya et al. (2023) demonstrated the effectiveness of the combination of 0.5 ml IU HCG and 0.5 ml kg⁻¹ Ovaprim for inducing the breeding of climbing perch. However, the application of the OVASPEC hormone in climbing perch, A. testudineus, has not been reported despite its potential importance as cost-effective and widely available alternative for induced breeding of fish.

OVASPEC is a synthetic reproductive hormone that contains a salmon analog gonadotrophin-releasing hormone (sGnRH-a) and anti-dopamine. This hormone plays an important role in triggering the endogenous gonadotropin hormone release that further induces ovulation and the spawning process in fish (Sukendi, 1995). The successful breeding and seed production using OVASPEC hormone have been reported in two species of fish, namely, peres fish Osteochilus kappeni (Faisal and Komariyah, 2021) and seluang fish Rasbora einthovenii (Syarif et al., 2021). However, the use of OVASPEC hormone in climbing perch has not been reported previously. Therefore, this study aims to determine the optimal dose of OVASPEC hormone for the induced breeding and seed production in climbing perch.

The ANOVA test results show that differences in OVASPEC dose had a significant effect on latency period, fertilization, hatching, and survival rates of climbing perch (p < 0.05). The results indicated that a significantly low latency period was observed in the dosage of 0.7 ml kg⁻¹ BW (398.3 min) compared to other treatments (p < 0.05). The highest fertilization rate and hatching rates were obtained in the dosage of 0.5 ml kg⁻¹ BW with the value of 91.33% and 92.34%, respectively.

These values were significantly different from the 0.1 ml kg⁻¹ BW and 0.3 ml kg⁻¹ BW dosages but not significantly different from the dosage of 0.7 ml kg⁻¹ BW (p >0.05). The highest percentage of larval survival was also obtained by 0.5 ml kg⁻¹ BW treatment (97.38%), and this value was significantly different from the 0.1 ml kg⁻¹ BW treatment but was not significantly different from other treatments (p > 0.05) (Table 1).

The ANOVA test results also reveal that the differences in the dose of OVASPEC hormone had a significant effect on egg diameter (p < 0.05). The results showed that the highest egg diameter was found in the dosage of 0.7 ml kg⁻¹ BW (4,372 μm), and this value was significantly different from other treatments (Table 2).

The study showed that increasing the dose of OVASPEC hormone resulted in reduction in the latency period and effectively accelerated the ovulation process. This effect is probably due to the dose-dependent increase in GnRH hormone, which in turn accelerates the stimulation of the pituitary gland to produce enhanced gonadotropin hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH plays a role in oocyte development (vitellogenesis), while LH functions in oocyte maturation to accelerate the process of ovulation (Sukendi, 2001). The OVASPEC also contains an anti-dopamine (dopamine blocker), which functions to inhibit the action of dopamine. This dopamine hormone can block the production of gonadotropin hormones (LH and FSH) (Rottmann et al., 1991; Bryant et al., 2016). Hence, in the presence of a dopamine blocker, the dopamine hormone is not secreted, allowing the LH and FSH hormones to act optimally and to accelerate gonadal maturation (Hoar et al., 1983; Hill et al., 2009). This study shows that the application of OVAPSEC at the dose of 0.5 ml kg⁻¹ BW gave better results compared to other tested hormone doses, with fertilization, hatching, and survival rates of 91.3%, 92.34%, and 97.38%, respectively. However, the recorded fertilization and hatching rates in this study were lower than those reported by Choresca et al. (2024) with the values of 99.13% and 97.50%, but the larval survival rates were higher than those reported in previous reports of 84.69%.

In addition, the results of the present study were higher than the performance of Ovaprim at the same dose on climbing perch, which produced fertilization and hatching rates of 75.11% and 78.09%, respectively (Saptono et al., 2018). This suggests that OVASPEC is found to be more effective than Ovaprim in climbing perch. Further, the study also shows that the hormone dose of 0.5 ml kg⁻¹ BW OVASPEC increased hatching and a larval survival rates above 90%. However, the increased hormone dose of OVASPEC more than 0.5 ml kg⁻¹ BW decreased egg quality, fertilization, and hatching rates at the dosage of 0.7 ml kg⁻¹ BW. Increasing the OVASPEC dosage, in addition to resulting in a short latency period, also causes the eggs to develop bigger, but the fertility and hatching rates decreased. This indicates that although the egg size was increasing, their quality was decreasing as described above. This is likely due to the hormone dosage exceeding the optimum limit (overdose), resulting in an excessively high level of gonadotropin in the blood, this causes the vitellogenesis process to accelerate, leading to overripe eggs. This is in agreement with I'tishom (2008), who stated that hormones work optimally at the suitable dose. The use of an inappropriate dosage reduces the biological potential of fish, as seen in the fertilization and hatching rates recorded in this study.

The application of high doses of productive hormones caused early ovulation and ovulatory eggs to remain in the ovarian lumen in hypoxic conditions, which led to a decrease in egg quality (Dewantoro, 2017). According to Fujaya (2004), the administration of overdose hormones can reduce the potential of fertilization and hatching rate, result in low-quality larvae, and also decrease the survival rate. However, egg hatching and survival are not only influenced by egg quality but also affected by environmental factors such as temperature, dissolved oxygen, and pH. The water quality parameters for the experimental water were a temperature of 26–27 °C, dissolved oxygen levels of 5.40–5.43 mg L⁻¹, and a pH of 7.0. However, the optimum temperature for the hatching of climbing perch fish eggs was 26–29 °C, dissolved oxygen 2–5 mg L⁻¹, and pH 6.5–7.5 (Marlida, 2001). Therefore, the water quality ranges are still suitable for the hatching and survival of climbing perch A. testudineus larvae.

This study, along with previous reports by Choresca et al. (2024), Aya et al. (2023), and Maulida et al. (2022; 2023; 2024), has addressed the problems of climbing perch breeding. However, still other challenges remain; for instance, the nutritional requirements of larval stages are crucial and need to be explored intensively (Putra et al., 2016) for hatchery seed production and commercial culture of this valuable fish species.

The dose of OVASPEC hormone had a significant effect on the latency period, fertilization rate, hatching of eggs, and survival rates of climbing perch Anabas testudineus larvae. The study recommends 0.5 ml kg⁻¹ BW as the optimal dose of OVASPEC for successful breeding and seed production of climbing perch.