Reproductive aspects of native and endangered wild Betta fish (Betta dennisyongi and Betta rubra) from Aceh waters, Indonesia

Aspectos reprodutivos de peixes Betta selvagens nativos e ameaçados de extinção (Betta dennisyongi e Betta rubra) das águas de Aceh, Indonésia

Abstract

Betta dennisyongi and Betta rubra are ornamental fish native to Aceh waters, facing a decline in population due to overexploitation and environmental changes. Therefore, this research aimed to obtain information regarding the reproduction of B. dennisyongi and B. rubra. The study was conducted from January to December 2020, with B. dennisyongi and B. rubra samples collected from Nagan Raya Regency and Aceh Besar, respectively. Approximately 1,099 Betta fish samples were successfully collected, comprising 600 B. dennisyongi and 499 B. rubra. The results showed that sex ratio (male:female) analysis had 1:5 and 1:6 for B. dennisyongi and B. rubra, respectively, indicating a predominance of female. Further analysis showed that only 15% of female B. dennisyongi samples had mature gonads out of 505 and 3.7% of male among 95 B. dennisyongi. Female of B. dennisyongi showed first mature gonads at a size of 3.86 cm, while male had maturity at 3.99 cm. For B. rubra, only 11.1% of female and 26.9% of male samples showed mature gonads out of 432 and 67, respectively. Female of B. rubra first matured gonads at a size of 3.86 cm, while male had maturity at 3.90 cm. Reproductive analysis showed that both species were continuous spawners in the year, as indicated by mature gonads in each month of observation, with fluctuating percentages. The peak spawning period for B. dennisyongi occurred in October, while B. rubra was observed in January. Consequently, it was recommended not to catch these species during their spawning months to maintain the sustainability of these endangered species.

Keywords:
Aceh Besar; Nagan Raya; reproduction; Sundaland

Resumo

Betta dennisyongi e Betta rubra são peixes ornamentais nativos das águas de Aceh, que enfrentam um declínio populacional devido à superexploração e mudanças ambientais. Portanto, esta pesquisa teve como objetivo obter informações sobre a reprodução dessas duas espécies. O estudo foi conduzido de janeiro a dezembro de 2020, com amostras de B. dennisyongi e B. rubra coletadas em Nagan Raya Regency e Aceh Besar, respectivamente. Aproximadamente 1.099 amostras de peixes Betta foram coletadas, compreendendo 600 B. dennisyongi e 499 B. rubra. Os resultados mostraram que a análise da proporção sexual (macho:fêmea) foi de 1:5 e 1:6 para B. dennisyongi e B. rubra, respectivamente, indicando uma predominância de fêmeas. Análises posteriores mostraram que apenas 15% das amostras de fêmeas de B. dennisyongi tinham gônadas maduras (de um total de 505), enquanto entre os 95 machos analisados, apenas 3,7% estavam sexualmente maduros. A fêmea de B. dennisyongi apresentou as primeiras gônadas maduras com um tamanho de 3,86 cm, enquanto o macho teve maturidade com 3,99 cm. Para B. rubra, apenas 11,1% das amostras de fêmeas e 26,9% dos machos apresentaram gônadas maduras de 432 e 67, respectivamente. A fêmea de B. rubra apresentou as primeiras gônadas maduras com um tamanho de 3,86 cm, enquanto o macho teve maturidade com 3,90 cm. A análise reprodutiva mostrou que ambas as espécies foram reprodutoras contínuas ao longo do ano, conforme indicado pelas gônadas maduras em cada mês de observação, com percentuais flutuantes. O pico do período de desova para B. dennisyongi ocorreu em outubro, enquanto o de B. rubra se deu em janeiro. Recomenda-se não capturar ambas as espécies durante os meses de desova, para manter a sustentabilidade dessas espécies ameaçadas.

Palavras-chave:
Aceh Besar; Nagan Raya; reprodução; Sundalândia

1. Introduction

Freshwater ecosystems such as rivers, lakes, and wetlands are experiencing a biodiversity crisis. This crisis is caused by human activities that pose threats to the sustainability of freshwater biodiversity (Reid et al., 2019; Tickner et al., 2020; Albert et al., 2021; Ottoni et al., 2023; Sayer et al., 2025) to population decline (Dudgeon et al., 2006). One species that is affected by environmental damage is the Betta fish. In Indonesian waters, there are approximately 53 species of Betta fish, comprising 71.6% of the 74 species worldwide (Froese and Pauly, 2025). Among this distribution, four species are identified in Aceh waters (Nur et al., 2022), two of which are native, namely Betta dennisyongi Tan 2013 and Betta rubra Perugia 1893. Currently, the supply for the trade of B. rubra and B. dennisyongi relies heavily on wild catches, posing a potential threat to their populations in natural habitat. This phenomenon is increased by habitat degradation in various regions due to land use conversion into plantations, roads, and residential areas. According to the IUCN (International Union for Conservation of Nature) Red List of Threatened Species data, B. dennisyongi is considered vulnerable, while B. rubra is endangered (IUCN, 2020). The fish that are commercially traded are sourced from the wild, leading to a reduction in populations, showing the form of measurement to ensure sustainability in natural habitats. Therefore, urgent management efforts, including conservation strategies, are essential to prevent the extinction of these natural treasures in Indonesia. Biological reproductive information is a crucial aspect of developing fish breeding programs (Abu‐Hakima, 1984; Muchlisin et al., 2010; Lowerre-Barbieri et al., 2011a; Muchlisin, 2014; Pensinger et al., 2021).

Based on reproductive behavior, Betta fish can be categorized into nest-builders and mouthbrooders. Nest-builders construct bubble nests for spawning and incubate the eggs in the bubbles. However, mouthbrooders incubate their eggs in the mouths (Alderton, 2012). B. rubra and B. dennisyongi belong to the mouth-brooding group, where male fish typically collects fertilized eggs and broods within its mouth. Male species search for refuge behind plant roots or debris until the eggs hatch (Schindler and van der Voort, 2011).

The reproduction of B. dennisyongi and B. rubra remains challenging due to the lack of information on reproductive biology, particularly sexual maturity, fecundity, and spawning periods. Therefore, understanding the reproductive biology of these fish is crucial for fisheries management planning (Jakobsen et al., 2016). The absence of adequate information can lead to failures in management and the development of cultivation programs (Kjesbu et al., 2009; Alves and Silva, 2012). There is currently limited research on the reproductive biology of Betta fish, with only B. pugnax from Damansara waters, Malaysia, being reported. This species spawns in the year, with a peak period during the rainy season in October-November (Kok-Jee, 1972). Despite the decline in population, the report specific to B. dennisyongi and B. rubra from Aceh, Indonesia, is still lacking. Therefore, this research aimed to analyze sex ratios, gonad maturity indices, spawning seasons, and fecundity of B. dennisyongi and B. rubra.

2. Materials and Methods

2.1. Time and site

This research was conducted from January to December 2020. Samples of B. dennisyongi were collected from Nagan Raya Regency, while B. rubra were obtained from Aceh Besar (Figure 1). The captured fish were kept alive and transported to the Breeding Laboratory at the Faculty of Marine and Fisheries, Universitas Syiah Kuala, Banda Aceh, for further analysis. B. dennisyongi samples were collected from three locations in Nagan Raya, namely Blang Neuang Village (04° 16.936”N and 096° 27.023”E), Blang Baro (04° 16.515”N and 096° 24.147”E), and Babah Krueng (04° 16.135”N and 096° 24.030”E). Meanwhile, B. rubra samples from Aceh Besar were collected from Bira Cot (05° 29.895”N and 095° 27.939”E). The sampling locations were selected based on information from residents. Fish samples were captured using scoop nets, transferred alive into sample bottles, and taken to the laboratory for further analysis. The captured fish were kept alive and transported to the Breeding Laboratory at the Faculty of Marine and Fisheries, Universitas Syiah Kuala, Banda Aceh, for further analysis. The fish were measured for total and standard length using digital calipers (Mitutoyo, CD-6CS. Error = 0.01 mm), and weight was recorded using a digital scale (Toledo, AB-204. Error = 0.01 g). Subsequently, the samples collected were euthanized using cold water (4 °C) for 3-5 minutes, followed by preservation in a 10% formalin solution (Ferreira et al., 2022)

Figure 1
Sampling locations of Betta spp. in Aceh Besar and Nagan Raya Districts, Indonesia.

2.2. Gonad observation

A total of 600 B. dennisyongi were successfully collected from Nagan Raya, and 499 B. rubra from the waters of Aceh Besar. In this research, the collected fish were dissected to observe sex.

2.3. Gonad maturity stage and Gonadosomatic index (GSI) analyses

Visual observations of gonad maturation were conducted following Brown et al. (2014) for female Betta fish and Lim et al. (2014) for male. These observations aimed to determine the maturation of female (ovary) and male (testis) reproductive organs, providing insights into the size at which fish first reach sexual maturity. Gonadosomatic index (GSI) was calculated according to Amtyaz et al. (2013) (Equation 1):

$$GSI\left(\%\right)=\frac{\text{Weight of gonad}}{Bodyweight}\text{x}100$$ (1)

2.4. Sex dimorphism, sex ratio, and fecundity analyses

Observation of sex dimorphism aimed to distinguish male and female fish (physical appearance) morphologically. Fish samples were visually examined, considering body shape and color. Sex ratio observation was performed to determine the ratio of male to female in a population. Observations of sex dimorphism and gonad maturity stage allowed for the precise identification of sex of each fish sample, enabling the calculation of the ratio of female to male. Sex ratio was calculated using the Formula 2 by Adebiyi (2013):

$\text{Sex ratio}=\frac{\text{Number of males}}{\text{Number of females}}$ (2)

Fecundity observation analyzed the reproductive capability of Betta fish. Absolute fecundity was calculated by directly counting the number of fish eggs using a stereo microscope (Meiji Techno Microscopes, Made in Japan).

2.5. Size at maturity (SAM) and spawning frequency

Size at maturity (SAM) provides information about the proportion of mature at a specific size. The length and age at sex change were estimated for each species using the logistic Equation 3 by Williams et al. (2008):

$PL=(1+e^{-\text{ln}\left(19\right)\left(L-L_{50}\right)/{(L_{95}-L_{50})}^{-1}}$ (3)

where PL is the proportion of mature fish at length L, where L50​ and L95​ represent lengths at which 50% and 95% of fish are mature, respectively. Spawning frequency, representing the number of days between spawnings, was calculated by dividing 100 (representing the total fish population) by the percentage of fish with mature gonads (Muchlisin et al., 2011).

2.6. Data analysis

A chi-square contingency table (12 × 2) was used to detect significant differences in size, class sex ratio, and monthly (male and female) GSI among species. Reproductive organ weight and length data were analyzed using GraphPad Prism 8, and the results were presented in tables and figures.

3. Results

3.1. Gonad maturation stage and Gonadosomatic index (GSI) analyses

B. dennisyongi and B. rubra show apparent sexual dimorphism in terms of weight, size, and body color, with male being brighter and larger than female (Figure 2). A total of 1,099 samples of Betta fish, comprising 600 B. dennisyongi and 499 B. rubra, were successfully collected during the 12-month period. The monthly sex ratio significantly changed in both species (B. dennisyongi χ2 = 102.19, p < 0.05; B. rubra χ2 = 46.66, p < 0.05). There was a significant difference in sex ratio per size class for both species (B. dennisyongi χ2 = 347.21, p < 0.05, B. rubra χ2 = 409.09, p < 0.05). Captured B. rubra showed standard lengths (SL) ranging from 9.82 to 37.17 mm SL and weights 0.02-1.02 g. Meanwhile, B. dennisyongi showed weight ranging from 0.001 to 0.85 g and standard lengths from 3.95 to 32.62 mm (Table 1). Observation of the gonad maturation stage showed that most female B. dennisyongi reached gonad maturation in October, spawning every 2 days, while male matured in May, spawning every 5 days (Table 2). For B. rubra, most female matured in January with a spawning frequency of 2 days, and male matured in July with a spawning frequency of 3 days (Table 3). Analysis results indicated that out of 505 female B. dennisyongi, only 76 (15%) showed gonad maturation. Among 95 males, only 16 (3.7%) showed gonad maturation (Figure 3a, b). Similarly, among 432 female and 67 male B. rubra, only 48 (11.1%) and 18 samples (26.9%) showed gonad maturation, respectively (Figure 3c, d).

Figure 2
(a) male B. rubra; (b) female B. rubra; (c) male B. dennisyongi; (d) female B. dennisyongi.

Table 1
Measurements of standard length, total length, and weight of Betta fish collected from waters in Aceh, Indonesia.

Species	n	Standard length (mm)		Total length (mm)		Weight (g)
		Range	Mean±SD	Range	Mean±SD	Range	Mean Mean±SD
Betta dennisyongi	600	3.95-32.62	20.11±5.57	5.04-57.81	25.97±7.68	0.001-0.85	0.22±0.17
Betta rubra	499	9.82-37.17	21.87±5.91	12.12-45.45	27.88±7.57	0.02-1.02	0.26±0.22

Table 2
Gonadal maturity level and gonadosomatic index (GSI) of Betta dennisyongi.

Month	Female (n)	Presentation of mature gonadal female Betta dennisyongi (%)							Spawning frequency (days)	GSI min-max (mean±SD)	Presentation of mature gonadal male Betta dennisyongi (%)							Spawning frequency (days)	GSI min-max (mean±SD)	Male (n)
		I	II	III	IV	V	Gonadal development (%)				I	II	III	IV	V	Gonadal development (%)
							Immature	Mature								Immature	Mature
January	40	95.00	0.00	0.00	0.00	5.00	100.00	0.00	0	0.02-1.21 (0.13±0.19)	90.00	0.00	0.00	0.00	10.00	100	0.00	0	0.07-0.91 (0.25±0.24)	10
February	45	44.44	28.89	13.33	11.11	2.22	75.56	24.44	4	0.03-6.13 (0.89±1.77)	40.00	60.00	0.00	0.00	0.00	100	0.00	0	0.04-1.04 (0.47±0.50)	5
March	46	63.04	8.70	17.39	6.52	4.35	76.09	23.91	4	0.02-6.72 (0.76±1.49)	75.00	25.00	0.00	0.00	0.00	100	0.00	0	0.09-0.17 (0.12±0.04)	4
April	44	77.27	9.09	2.27	4.55	6.82	93.18	6.82	15	0.03-9.17 (0.57±1.44)	83.33	0.00	0.00	0.00	16.67	100	0.00	0	0.06-1.03 (0.40±0.42)	6
May	46	73.33	13.33	2.22	0.00	11.11	97.78	2.22	45	0.02-2.46 (0.51±0.56)	80.00	0.00	20.00	0.00	0.00	80	20.00	5	0.20-2.46 (0.79±0.94)	4
June	48	47.92	18.75	10.42	12.50	10.42	77.08	22.92	4	0.05-6.08 (0.95±1.37)	100.00	0.00	0.00	0.00	0.00	100	0.00	0	0.34--43 (0.39±0.06)	2
July	47	72.34	8.51	10.64	4.26	4.26	85.11	14.89	7	0.03-7.57 (0.89±1.65)	100.00	0.00	0.00	0.00	0.00	100	0.00	0	0.11-0.14 (0.13±0.02)	3
August	50	54.00	18.00	10.00	8.00	10.00	82.00	18.00	6	0.03-12.29 (1.47±3.01)	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a
September	49	59.18	14.29	6.12	10.20	10.20	83.67	16.33	6	0.05-12.04 (1.75±3.07)	0.00	100.00	0.00	0.00	0.00	100	0.00	0	0.61	1
October	27	51.85	7.41	25.93	14.81	0.00	59.26	40.74	2	0.009-9.95 (3.13±3.60)	91.30	8.70	0.00	0.00	0.00	100	0.00	0	0.10-1.21 (0.35±0.27)	23
November	29	79.31	3.45	10.34	0.00	6.90	89.66	10.34	10	0.06-6.30 (0.77±1.49)	80.95	9.52	0.00	0.00	0.00	90	0.00	0	0.07 -0.64 (0.30±0.16)	21
December	34	100.00	0.00	0.00	0.00	0.00	100.00	0.00	0	0.03-0.33 (0.10±0.07)	93.75	0.00	0.00	0.00	6.25	100	0.00	0	0.04-0.25 (0.12±0.06)	16

Table 3
Gonadal maturity level and gonadosomatic index (GSI) of Betta rubra.

Month	Female (n)	Presentation of mature gonadal female Betta rubra (%)							Spawning frequency (days)	GSI min-max (mean±SD)	Presentation of mature gonadal male Betta rubra (%)							Spawning frequency (days)	GSI min-max (mean±SD)	Male (n)
		I	II	III	IV	V	Gonadal development (%)				I	II	III	IV	V	Gonadal development (%)
							Immature	Mature								Immature	Mature
January	19	15.79	15.79	21.05	21.05	26.32	57.89	42.11	2	0.14-9.11 (1.84±2.57)	0.00	33.33	33.33	0.00	33.33	66.67	33.33	3	0.18-0.48 (0.33±0.15)	3
February	24	66.67	12.50	12.50	8.33	0.00	79.17	20.83	5	0.05-18.15 (2.08±4.08)	0.00	0.00	0.00	0.00	100.00	100.00	0.00	0	0.28	1
March	48	66.67	14.58	4.17	4.17	10.42	91.67	8.33	12	0.06-5.12 (0.79±1.01)	0.00	50.00	0.00	0.00	50.00	100.00	0.00	0	0.19-0.33 (0.26±0.10)	2
April	43	76.74	16.28	4.65	2.33	0.00	93.02	6.98	14	0.05-3.36 (0.50±0.66)	42.86	28.57	14.29	14.29	0.00	71.43	28.57	4	0.07-2.96 (0.57±1.05)	7
May	50	82.00	14.00	0.00	2.00	2.00	98.00	2.00	50	0.06-9.89 (0.61±1.40)	n/a	n/a	n/a	n/a	n/a	n/a	n/a	0	n/a	n/a
June	38	60.53	26.32	5.26	2.63	5.26	92.11	7.89	13	0.04-5.79 (0.86±1.19)	33.33	22.22	22.22	11.11	11.11	66.67	33.33	3	0.04-0.34 (0.23±0.09)	9
July	26	46.15	23.08	7.69	7.69	15.38	84.62	15.38	7	0.11-13.16 (1.30±2.83)	9.09	9.09	27.27	27.27	27.27	45.45	54.55	2	0.13-1.92 (0.43±0.51)	11
August	47	78.72	2.13	12.77	6.38	0.00	80.85	19.15	5	0.03-8.59 (0.95±1.62)	33.33	33.33	0.00	33.33	0.00	66.67	33.33	3	0.18-0.76 (0.36±0.27)	3
September	44	84.09	11.36	0.00	4.55	0.00	95.45	4.55	22	0.05-4.34 (0.55±0.85)	0.00	83.33	0.00	16.67	0.00	83.33	16.67	6	0.24-0.67 (0.44±0.16)	6
October	37	83.78	8.11	2.70	5.41	0.00	91.89	8.11	12	0.05-4.95 (0.56±0.93)	69.23	7.69	7.69	15.38	0.00	76.92	23.08	4	0.07-0.69 (0.24±0.18)	13
November	44	70.45	11.36	4.55	4.55	9.09	90.91	9.09	11	0.05-11.80 (0.89±1.99)	66.67	0.00	0.00	0.00	33.33	100.00	0.00	0	0.19-1.76 (0.53±0.61)	6
December	12	58.33	16.67	8.33	8.33	8.33	83.33	16.67	6	0.10-2.52 (0.79±0.79)	11.11	22.22	11.11	0.00	22.22	55.56	11.11	9	0.09-0.92 (0.34±0.32)	6

Figure 3
Gonadal maturity frequency of Betta fish during a year of study. where (a) female Betta dennisyongi (total 76 samples); (b) male Betta dennisyongi (total 14 samples); (c) female Betta rubra (total 48 samples); (d) male Betta rubra (total 18 samples).

3.2. Size at the first maturity and sex ratio

Frequency length analysis divided female B. dennisyongi and B. rubra into 8 length classes, while male of both species were grouped into 5 length classes (Figure 3). Female B. dennisyongi typically showed gonad maturation in the 25-44 mm and male matured at 21-36 mm (Figure 3a, b). In B. rubra, female showed gonad maturation at 30-41 mm and male at lengths of 30-41 mm (Figure 3c, d). Size at the first maturity analysis indicated that female B. dennisyongi matured at a length of 3.86 cm (Figure 4a) and male at 3.99 cm (Figure 4b). Similarly, in B. rubra, female first matured at a length of 3.86 mm (Figure 4c) and male at 3.90 cm (Figure 4d). Sex ratio of mature gonad fish in B. dennisyongi showed a ratio of 1:4.8 (male:female), where the number of mature gonad female B. dennisyongi was 4.75 times greater than male. In B. rubra, the ratio of mature gonad male to female was 1:2.67, with mature gonad female B. rubra being 2.67 times more numerous than male. The analysis results showed that female fish were more dominant in both B. dennisyongi and B. rubra, with the highest found in August for B. dennisyongi and May for B. rubra (Table 4). However, GSI of male (p > 0.05, χ2 = 9.92, df = 11) and female (p > 0.05, χ2 = 5.00, df = 11) of both species did not differ.

Figure 4
L50 size of gonadal mature Betta fish: (a) female Betta dennisyongi; (b) male Betta dennisyongi; (c) female Betta rubra; (d) male Betta rubra (: Observation and : Measurement).

Table 4
Sex ratio of Betta dennisyongi and Betta rubra based on the month of observation.

Month	Betta dennisyongi				Betta rubra
	Sex (Ind)		Ratio sex		Sex (Ind)		Ratio sex
	Male	Female	Male	Female	Male	Female	Male	Female
January	10	40	1	4	3	19	1	6.33
February	5	45	1	9	1	24	1	24
March	4	46	1	11.5	2	48	1	24
April	6	44	1	7.33	7	43	1	6.14
May	4	46	1	11.5	0	50	0	50
June	2	48	1	24	9	38	1	4.22
July	3	47	1	15.67	11	26	1	2.36
August	0	50	0	50	3	47	1	15.67
September	1	49	1	49	6	44	1	7.33
October	23	27	1	1.17	13	37	1	2.85
November	21	29	1	1.38	6	44	1	7.33
December	16	34	1	2.13	9	12	1	1.33
Total	95	505	1	5	70	432	1	6.17

3.3. Fecundity

Total fecundity (TF) analysis for B. dennisyongi ranged from 20 to 68 eggs/female or an average with standard deviation (±SD) of 37.47±7.43 eggs/female. Relative fecundity (RF) ranged from 0.01 to 7.53 eggs/gram body weight with an average of 2.38±1.95 eggs/gram for B. dennisyongi. For B. rubra, fecundity ranged from 30 to 73 eggs/female with an average of 46.57±9.69 eggs/female, and RF ranged from 0.06 to 8.55 eggs/female or 2.12±1.81 eggs/gram body weight (Table 5). Correlation coefficient (r) analysis between fecundity and length in B. rubra showed a low relationship (r2 = 0.27), while in B. dennisyongi, it showed a weak correlation (r2 = 0.47) (Figure 5a, b). The highest fecundity for B. dennisyongi based on length class was found in the 39.9-42.4 mm length class, reaching 46.67 eggs/ind. The length class with the highest fecundity in B. rubra was in the 30.0-32.2 mm length class, reaching 60.00 eggs/ind (Figure 5c, d).

Table 5
Total fecundity (FT) and relative fecundity (FR) of Betta fish from Aceh waters.

Species	∑ Ind (n)	Standard length	Total length	Weight (gram)	Total fecundity (eggs/individual)	Relative fecundity (eggs/gram of fish)
		(mm)	(mm)
Betta dennisyongi	64	20.20-32.62 (27.11±3.24)	24.80-42.36 (35.04±4.30)	0.18-0.77 (0.43±0.15)	20-68 (37.47±7.43)	0.01-7.53 (2.38±1.95)
Betta rubra	46	23.80-34.93 (30.49±2.86)	30.04-45.06 (39.24±3.47)	0.35-1.02 (0.64±0.61)	30-73 (46.57±9.69)	0.06-8.55 (2.12±1.81)

Figure 5
(a, b) Correlation between length and fecundity; (c, d) average fecundity based on length classes in Betta fish.

4. Discussion

Betta dennisyongi and Betta rubra exhibit apparent sexual dimorphism in terms of weight, size, and body color, with males being brighter and larger than females. This aligns with the findings of Jaroensutasinee and Jaroensutasinee (2025), who reported similar traits in male B. splendens Regan 1910 from Nakhon Si Thammarat, Thailand. Biokani et al. (2014) further noted that young bettas only develop color after about three months, making it easier to distinguish between males and females after 3 months, reaching gonadal maturity at 5 months. In addition to being larger and brighter, males also have longer fins (Smith, 1945; Braddock and Braddock, 1955; Simpson, 1968; Biokani et al., 2014).

Reproductive analysis of B. dennisyongi and B. rubra in this study indicates that both species spawn throughout the year (multiple spawners), as evidenced by fluctuations in the percentage of males and females with mature gonads in each month of observation. The highest percentage of mature gonads in male and female B. dennisyongi was observed in May and October, while for B. rubra, it was in January and July, predicting the peak spawning of these species during those months. The analysis of mean total fecundity shows values of 37.47±7.43 eggs/individual for B. dennisyongi and 46.57±9.69 eggs/individual for B. rubra. These values are lower than other betta species; for example, B. splendens can produce up to 2,184 eggs in a single spawning season (Reyes-Bustamante and Ortega-Salas, 2002). Low fecundity can lead to low recruitment, resulting in small populations in the wild and susceptibility to overfishing. This aligns with Hutchings (2000) statement that overfishing causes a significant decline in fish populations. Pörtner et al. (2001) added that a decrease in fish population fecundity can also be caused by environmental factors, where energy allocation for reproduction is only possible after physiological homeostasis requirements are met (Wieser, 1994). Correlation analysis between fecundity and fish size shows a weak relationship(r=0.27-0.47), indicating that an increase in fish size does not significantly contribute to an increase in the number of eggs. The low fecundity of B. dennisyongi and B. rubra may be related to their parental care nature, as both species are mouthbrooders, incubating eggs and larvae in their mouths (Oppenheimer, 1970). According to Priyadi et al. (2024), Spawning in B. rubra occurs after 1–2 weeks. After successful spawning, the embryogenesis process of B. rubra fish takes six days, and the fish larvae enter a rapid exponential growth phase until day 39.

Mouthbrooder behavior can negatively affect parents (Reardon and Chapman, 2010; Keller et al., 2017; Sawecki et al., 2019). During egg incubation, the ability of parent to eat and respire is disrupted, only searching for food after the incubation period (Morley and Balshine, 2003; Schürch and Taborsky, 2005; Abecia et al., 2022). The cessation of feeding and the use of stored resources to maintain physiological processes during incubation can lead to a decline in the body condition of parent. However, prolonged incubation periods have potential to cause the death of the parent (Smith and Wootton, 1994; Okuda and Yanagisawa, 1996; Grüter and Taborsky, 2004; Abecia et al., 2022). Male mouthbrooder Betta fish will incubate eggs in their mouths for approximately 4 weeks (Schmidt, 1996). During this period, male fish become more aggressive as the offspring age (Jaroensutasinee and Jaroensutasinee, 2003). The parental care behavior of mouthbrooder focuses on increasing the survival chances of their offspring (Klug and Bonsall, 2010; Klug et al., 2012) and providing a suitable environment for growth and development (Oppenheimer, 1970; Keenleyside, 1991). Vierke (1991) added that mouthbrooding behavior adapts to habitat and predation risks. The mouthbrooder classification restricts the quantity of offspring that betta fish can rear, thereby affecting the limited number of progeny produced. This process complicates natural population growth unless managed judiciously. Research conducted by Priyadi et al. (2024) indicated that among 73 ova, only 34 successfully hatched.

The analysis of gonad maturation in both types of Betta fish in this research indicates that female fish mature gonads earlier than male. The size at which fish first mature gonads is considered an indication of overfishing, where overexploited fish tend to mature earlier or at a smaller size. This phenomenon has also been reported by Muchlisin et al. (2010) in Rasbora tawarensis and Efizon et al. (2021) in Barbonymus sp. from Aceh waters, where both types of fish experience overfishing. Therefore, further research is essential on the stock status of B. dennisyongi and B. rubra in Aceh waters.

Sex ratio analysis for B. dennisyongi is 1:5 (male:female) and 1:6 for B. rubra, indicating a predominance of female. Similar reports have been documented for other betta species in different waters, such as B. raja in Bandar Tinggi Village, Indonesia, Manullang and Khairul (2020). B. splendens were also identified in the common waters of Riau reservoirs (Purnomo, 2019) and Thailand (Watson et al., 2019). However, sex ratio of B. splendens in Nakhon Si Thammarat Province, Thailand, is reportedly balanced (Jaroensutasinee and Jaroensutasinee, 2025). Theoretically, an imbalanced sex ratio is capable of increasing the vulnerability of fish population sustainability. This is because fewer male can cause lower egg fertilization opportunities, leading to decreased fish recruitment. However, the low male-to-female ratio in both betta species in this research is related to the reduced fecundity of female, producing approximately 20 to 73 eggs in one spawning season. The assumption is that the low ratio of male fish may be due to excessive exploitation, attractive colors, higher market value, and use in betta fish. Udo et al. (2016) also suggested that the higher number of females than males could be because females had a longer lifespan. Additionally, sex ratio is influenced by reproductive activities (Matoba, 1977) and the conditions of fish and their environment (Cushing, 1973; Lowerre-Barbieri et al., 2011b).

5. Conclusion

In conclusion, this research showed that female B. dennisyongi and B. rubra reached gonadal maturity at a smaller size compared to male. Both species spawned in the year, with the peak occurring in October and January for B. dennisyongi and B. rubra, respectively. Female sex ratio was more dominant in both betta species, while fecundity was considered low.

Acknowledgements

This study was supported by the Universitas Syiah Kuala through Riset Unggulan Unsyiah Percepatan Doktor (PRUUPD) 2022 (Contract Number: 487/UN11/SPK/PNBP/2022). Therefore, the authors are grateful to the Rector of the Universitas Syiah Kuala for their support.

Data Availability Statement

The research data are only available upon request to the corresponding author.

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Edited by

• Editor:
  Felipe P. Ottoni

Publication Dates

• Publication in this collection
  15 Sept 2025
• Date of issue
  2025

History

• Received
  18 Sept 2024
• Accepted
  23 Apr 2025