The snakeskin gourami, Trichopodus pectoralis (Regan, 1910), commonly known as the Siamese gourami, is an economically important freshwater fish species. Consumers highly value it for its taste and year-round availability, and it is primarily marketed fresh or salted for human consumption. This species naturally inhabits various aquatic environments, including swamps, floodplains, rivers, and lakes [1,2]. In aquatic ecosystems, T. pectoralis helps control water hyacinth growth [3]. They are classified as an omnivorous species [4] and can survive in low-oxygen water [5]. This species can also be raised in many environments, including rice paddies, fish farms, and even specialized blue tanks [6-8]. Researchers have also successfully domesticated the species using genetic techniques [9]. Other scientists continue refining rearing techniques for this species [10,11].

In Southeast Asia, inland fisheries are increasingly recognized as integral to sustainable development, particularly in supporting rural livelihoods, food security, and local economies. In Indonesia, wetland fisheries provide an accessible and affordable source of protein while sustaining small-scale economic activities among riparian communities [12]. These systems are also shaped by strong socio-cultural dimensions, including traditional fishing practices that reflect accumulated ecological knowledge and adaptive resource use [1]. However, wetland ecosystems face increasing pressure from environmental degradation, climate variability, and fishing intensity, thereby requiring integrated approaches that link ecological understanding with development priorities [3,9].

Despite their ecological importance, T. pectoralis faces significant threats, including water pollution from chemical contaminants (e.g., potassium), overfishing, and wetland degradation [13]. Recognizing these threats, the IUCN Red List classifies this species as threatened [14]. Various conservation initiatives have been implemented to address these challenges and protect wild populations [15,16].

The length-weight relationship (LWR) is a fundamental tool in fisheries science, providing insights into fish growth patterns, condition factors, and overall health. By analyzing specimens from diverse freshwater systems over time, researchers can estimate expected weights at various lengths within a species, thereby informing assessments of population structure and dynamics [17]. However, reliance on LWR alone may overlook other critical aspects of fish biology. Parameters such as age, sex, gonadosomatic index (GSI), condition factor, and feeding behavior provide additional information related to reproductive status, energy allocation, and ecological adaptation. When integrated with LWR data, these biological indicators improve comparative assessments across regions and species, which contributes to more effective fisheries management and conservation efforts [18].

Although numerous studies on T. pectoralis have been conducted, much of the previous research has primarily focused on aquaculture performance, domestication, feeding ecology, reproductive biology, and length–weight relationships in specific habitats [1-2, 9]. Several studies have also investigated growth patterns and condition factors in different freshwater ecosystems across Southeast Asia [19-21]. However, information regarding the interaction between traditional fishing practices and the biological characteristics of T. pectoralis populations remains limited, particularly in wetland ecosystems of Central Kalimantan. In addition, studies integrating growth pattern, condition factor, length at first maturity, and length at first capture within a fisheries management context remain scarce.

By addressing these gaps, the present study is expected to expand the existing knowledge of the biological status of T. pectoralis in a tropical wetland ecosystem where traditional fishing practices remain important. The findings may provide a scientific basis for assessing the status of the exploited fish population and informing size-based and adaptive fisheries management of T. pectoralis in Palangkaraya City.

Several traditional fishing gears have been reported for capturing T. pectoralis in South Kalimantan Province, including Tempirai (wire stage trap), Lalangit (horizontal set gillnet), Lunta (cast net), Hancau (portable liftnet), Lukah (fish pots), and pancing (hook and line) [22,23]. However, studies by Rusmilyansari et al. [22] and Mardhiyah et al. [23] did not evaluate potential interactions between fishing practices and the biological characteristics of the captured fish population. In Palangkaraya City, local fishermen are uncertain about how their fishing activities might affect the growth and persistence of T. pectoralis populations within their fishing areas.

Therefore, this study aims to assess the growth pattern, condition factor, length at first maturity, and length at first capture of T. pectoralis in the wetlands of Palangkaraya City, providing evidence to support sustainable fisheries management. The findings are expected to contribute baseline biological information for size-based fisheries management and support the sustainable utilization of inland wetland fish resources.

2.1. Study Sites

This study was conducted at a single sampling location within the wetlands of Palangkaraya City, Central Kalimantan Province, Indonesia (Figure 1), located at 02°23′35″ S 113°59′24″ E. The study was intentionally restricted to this site to characterize the fish population in a representative wetland ecosystem where local fishers commonly encounter T. pectoralis. Research activities, including a preliminary survey, specimen collection, and subsequent data analysis, were conducted from March to June 2023.

2.2. Data Collection

A total of 164 T. pectoralis specimens were collected, comprising 84 males and 80 females, with total length ranging from 60 to 100 mm and body weight from 3.5 to 8.6 g. Fish were captured by local fishers using tempirai, lunta, and lukah (Figure 2) at a common fishing area. Therefore, the number of specimens analyzed was limited to the fish naturally captured during the sampling period. The characteristics of each fishing gear are described below:

1. Tempirai is a heart-shaped wire trap measuring 575 mm in height and 525 mm in width, with a 25 mm wide entrance slit. It is deployed in shallow water adjacent to plants and other aquatic vegetation without bait. The upper part of Tempirai emerges from the water, giving fish access to air. The size of Tempirai used in this study was relatively larger than that reported from Manarap Village, Banjar District [24].

2. Lukah is a tube-shaped fish trap made of bamboo measuring 1.5 m in length and 230 mm in diameter. Each trap has an entry funnel (160 mm diameter) and an exclusion funnel (60 mm diameter). A one-way valve, known as a hinjap, made of elastic bamboo (50 mm diameter), prevents fish from escaping. Compared to the Lukah used in Martapura Subdistrict [22], the Lukah used in this study was smaller. The trap is submerged at an angle of approximately 15 degrees to allow fish access to atmospheric oxygen at the water surface. It is typically deployed in shallow water near plants and other aquatic vegetation.

3. Lunta is a circular cast net constructed from monofilament nylon with a mesh size of 15 mm. The net, approximately 2.2 m in length with a 6-m radius, is equipped with iron rings weighing 3.5 kg. A 3.2 m handline with a diameter of 10 mm is used to cast and retrieve the net. The Lunta used in this study was smaller than that commonly found in Martapura Subdistrict [22]. It is operated in streams connected to the swamp waters.

Although the sample size (n = 164) was relatively limited for a four-month sampling period, it reflected the actual catch availability of T. pectoralis in the study area. Sampling was conducted consistently using traditional fishing gears at the designated sampling site, and the collected specimens represented a broad range of body sizes and both sexes, allowing the assessment of growth pattern, condition factor, and reproductive parameters. Nevertheless, it is acknowledged that a larger sample size and longer sampling period would further improve population representativeness.

2.3. Measurement and Size Distribution

The total length of each fish was measured from the tip of the snout to the end of the caudal fin to the nearest millimeter using a ruler calibrated against a Vernier caliper. Body weight was measured using a digital scale with 0.01 g precision (Dretec KS-233, Japan). Subsequently, the specimens were grouped into size classes for analysis. Each class consisted of individuals of similar length (5 mm intervals) and weight (5 g intervals).

2.4. Sexual Dimorphism

Male and female T. pectoralis exhibit pronounced sexual dimorphism. Males typically have more elongated, pointed dorsal fins, reddish pelvic fins, vivid coloration, and a slimmer body shape. In contrast, females have shorter and more rounded dorsal fins without reddish coloration, a more muted color pattern, and a rounder abdomen [2]. Figure 3 illustrates these morphological differences.

2.5. Sex Ratio

The sex ratio was determined by comparing the numbers of male and female specimens collected during the sampling period, following standard fisheries population analysis methods [25].

2.6. Length-Weight Relationship

The length-weight relationship (LWR) of the T. pectoralis specimens was analyzed using the equation [26]:

where W is body weight (g), L is total length (mm), a is the intercept, and b is the slope. It was linearized through logarithmic transformation (log W = log a + b log L). Residual analysis was conducted, and potential outliers were excluded to improve model accuracy. The significance of the b values for each sex was assessed using Student’s t-test to confirm that it was significantly different from the predictions for isometric growth (b = 3) [27].

Ideally, the b value should be between 2.5 and 3.5 to assess the overall health of the fish population [28]. If b = 3 (isometric growth), the fish grows proportionally and keeps its shape. If b > 3 (positive allometric growth), the fish gains weight faster than in length. If b < 3 (negative allometric growth), the fish increases in length faster than in weight. The determination coefficient (R²) and correlation coefficient (r) of the length-weight relationship were also calculated.

The weight-to-total length (W/TL) ratio was calculated for each individual as a simple body condition metric to describe fish weight relative to total length. This ratio was used only to characterize the sampled T. pectoralis population and was not intended as part of the LWR analysis.

2.7. Condition Factor

The length–weight relationship (LWR) data were subsequently used to estimate Fulton’s condition factor [29].

where K is Fulton’s condition factor, L is the total length (cm), and W is the weight (g). The multiplication factor of 100 standardizes the value to approximately 1, facilitating interpretation, where a higher condition factor value generally indicates better fish condition and health status.

2.8. Length at First Maturity

Length at first maturity (Lm₅₀), defined as the size at which 50% of females reach sexual maturity, was estimated using a logistic curve [25].

where P represents the proportion of mature females at a given total length (TL), e is the exponent, a is the intercept, b is the slope, and Lm₅₀ is the estimated length at which 50% of the population is sexually mature. The Lm₅₀ is calculated using the logarithmic transformation: Lm₅₀ = -a/b.

The analysis included individuals across all observed length classes, comprising both immature and mature individuals. Due to technical constraints, detailed gonadal examination and gonad maturity stage classification were not conducted, and gonad weight measurements were not collected; therefore, gonadosomatic index (GSI) analysis could not be performed in this study. Consequently, the estimated Lm₅₀ should be considered a preliminary approximation of the reproductive size characteristics of the sampled population.

2.9. Length at First Capture

The length at first capture (Lc₅₀) represents the total length at which 50% of the T. pectoralis population is caught by fishing gear. To estimate the Lc₅₀, the cumulative catch frequency (%) was plotted against total length (mm) and fitted to a logistic selectivity curve [30]. The length corresponding to 50% cumulative probability of capture was considered the Lc₅₀ value.

2.10. Statistical Analysis

For data analysis, Microsoft Excel and SPSS 18 were used. Statistical results are presented as mean ± standard error (SE) or as percentages and summarized in tables and figures. The Lilliefors test was applied to assess data normality and homogeneity [31]. Differences in catch size and condition factor between sexes were evaluated using a t-test. The male-to-female sex ratio was analyzed using a chi-square test. One-way ANOVA was applied to examine significant differences in fish body sizes among the three fishing gears. Statistical significance was set at p < 0.05.

3.1. Length Frequency

The overall size distribution of T. pectoralis caught using three traditional fishing gears showed a predominant length range of 60–100 mm. The size distribution of fish caught by Tempirai skewed toward larger fish, with the highest proportion in the 85–89 mm size class, followed by the 90–94 mm size class. The lowest proportion of fish was recorded in the 75–79 mm length class (Figure 4A). These results suggest that Tempirai tends to catch relatively larger T. pectoralis than Lunta and Lukah.

The size-frequency distributions of T. pectoralis caught by Lunta and Lukah were more evenly distributed across length classes than those of Tempirai. Lunta primarily caught T. pectoralis in the 75–79 mm length range, followed closely by the 65–69 mm and 80–84 mm length ranges. The lowest proportion of fish was recorded in the 100–104 mm length class (Figure 4B). Meanwhile, Lukah’s catch increased gradually toward larger sizes, with the highest percentage of catch in the 90–94 mm length class. The lowest proportion of fish was recorded in the 65–69 mm length class (Figure 4C). In other words, Lukah’s catch showed a size distribution comparable to Lunta’s, with a relatively even spread across the length ranges. No significant differences in total catch length were observed among the fishing gears used (p > 0.05).

3.2. Length-Weight Relationship

This study analyzed 164 specimens of T. pectoralis, comprising 84 males (51%) and 80 females (49%) (Table 1). The chi-square test revealed that the observed sex ratio did not significantly differ from the expected 1:1 ratio (χ² = 0.098, p > 0.05). The fish measured 60–100 mm in total length (83.45 ± 0.74 mm) and weighed 3.5–8.6 g (6.13 ± 0.11 g). The mean weight-to-total length (W/TL) ratio was 0.07, with values ranging from 0.05 to 0.09. Males averaged 83.61 ± 1.05 mm and 6.14 ± 0.16 g, while females averaged 83.29 ± 1.06 mm and 6.13 ± 0.16 g. Catch size did not differ significantly between males and females (p > 0.05).

Figure 5 presents the length-weight relationships (LWR) for pooled sexes, males, and females. The results indicated a negative allometric growth pattern, suggesting that fish length increased faster than body weight. The estimated b value was 1.8856, with a determination coefficient (R²) of 0.8511, indicating that over 85% of the variation in body weight is explained by length, reflecting a strong model fit. Furthermore, a very high correlation coefficient (r) of 0.9226 confirms a strong positive relationship between body length and body weight.

3.3. Condition Factor

Statistical analysis showed that the condition factor (K) of male and female T. pectoralis did not differ significantly (p > 0.05). The K value for males ranged from 0.78 to 1.99 (1.06 ± 0.02), while for females, values ranged from 0.80 to 2.04 (1.07 ± 0.06). Overall, these values indicate that the fish were in good health.

3.4. Length at First Maturity

The estimated length at first maturity (Lm₅₀) for male and female T. pectoralis was 85.76 mm and 85.63 mm, respectively (Table 2). These values were lower than the estimated length at first capture (Table 3), indicating that most individuals likely reached sexual maturity and reproduced before capture. No significant difference was observed in the Lm₅₀ between males and females (p > 0.05). The combined Lm₅₀ value was calculated using pooled data from both sexes to facilitate comparison with Lc₅₀ values.

3.5. Length at First Capture

Figure 6 presents the estimated Lc50 for T. pectoralis caught using Tempirai, Lunta, and Lukah. The estimated Lc₅₀ values were 91.73 mm, 93.36 mm, and 93.75 mm TL, respectively. These values represent the length at which 50% of the fish population is captured by each fishing gear. Variations in the curve shape and estimated Lc₅₀ value may be influenced by population characteristics, sample size, and local fishing practices. However, no significant differences in Lc₅₀ values were observed among the fishing gears (p > 0.05).

The length distribution of T. pectoralis observed in the present study was generally smaller than those reported from several other freshwater ecosystems in Southeast Asia (Table 4). This is reflected by the relatively low W/TL ratio (0.073) and the smaller average body size of fish collected from the wetlands of Palangkaraya City compared with populations from Sungai Batang, Semayang Lake, Lubuk Lampam floodplain, Agusan Marsh, and Esperanza Lake [1-2, 12, 19, 32], all of which also showed negative allometric growth patterns. In contrast, T. pectoralis populations from Bilah River, Patra Tani, and Sunye Lake exhibited higher W/TL ratios and positive allometric growth patterns [20-21, 33].

The predominance of relatively small-sized individuals in the present study may be associated with environmental conditions, food availability, habitat characteristics, or fishing pressure within the wetland ecosystem [13,19]. In addition, the use of traditional fishing gear may selectively capture smaller size classes. Despite the relatively small body size, the condition factor indicated that the sampled fish were generally in good physiological condition. These findings suggest that local environmental and fishing conditions may influence variability in size structure among T. pectoralis populations across different regions.

A key finding of the present study was the negative allometric growth pattern of T. pectoralis, indicated by a relatively low b-value (1.8856). This value was lower than those reported in previous studies, which ranged from 2.6409 to 3.2588. Similar low growth coefficients (b < 2) have also been reported in several freshwater fish species, such as fishes from the Imo River, Nigeria [34], and snow trout (Schizothorax richardsonii) from the Rajouri River, Himalayas [35], possibly due to seasonal fluctuations. When the b-value is below 3, fish tend to allocate more energy toward increasing body length rather than body weight [36]. Multiple factors may influence variability in growth coefficients, such as life stage, growth phase, genetics, habitat condition, and food availability [37,38]. The negative allometric growth observed in the present study may also be linked to the early onset of the dry season, which could influence water availability, habitat quality, and food resources. In addition, regional differences in growth patterns and condition factors among fish populations may partially reflect environmental variation across habitats, including temperature, habitat characteristics, and seasonal dynamics [39,40].

The estimated K value for the T. pectoralis population in the present study was lower than those reported from other populations, including Sungai Batang [19], Bilah River [20,21], and Lakea Dua [41]. Despite this, individuals inhabiting the swamp were generally in good condition. Variations in the K value may be influenced by physiological factors and environmental conditions, including intraspecific competition for space and food resources, interspecific interactions, the fish’s sex and maturity stage, its stomach contents, food availability, etc. [1,21]. This K value provides valuable insights in several key areas, including population comparisons, gonadalmaturation, and feeding activity [17,42]. Understanding the condition factor of fish is crucial for effective aquaculture management, particularly for assessing the health and condition of cultured fish. When fish condition factor declines with increasing length, it signals a need for management intervention. Strategies to address this may include improving feed quality, optimizing feeding ratios, and adjusting fish stocking density to minimize competition for food and space.

The estimated length at first capture (Lc₅₀) of T. pectoralis in the present study (92.95 ± 0.06 mm) was considerably lower than the Lc₅₀ value (173.10 mm) observed in Semayang Lake, East Kalimantan [12]. This indicates that individuals were generally recruited into the fishery at smaller sizes. These differences may reflect variation in fishing gear characteristics, fishing practices, habitat conditions, and population structure between locations. These findings highlight the importance of monitoring catch size composition and improving gear selectivity as precautionary measures for sustainable management of T. pectoralis in wetland fisheries. High exploitation rates exceeding the optimum level have been reported for T. pectoralis populations in the Patra Tani floodplain and Semayang Lake (E = 0.53 and 0.62, respectively), whereas the population in Kayu Ara Baru, South Sumatra, was categorized as underexploited (E = 0.06) [12,13]. The estimated length at first maturity (85.70 mm) in the present study was lower than the length at first capture (92.95 mm), indicating that most of the fish had the opportunity to reproduce before being caught. However, the estimated Lm₅₀ in the present study was considerably smaller than that reported from Taliwang Lake, Sumbawa, West Nusa Tenggara (136 mm) [43].

Given the narrow sampling period and the fluctuating availability of mature individuals across sampling months, this study did not perform gonadosomatic index (GSI) analysis, as gonad weight measurements were not collected during sampling. Although limited by the relatively small sample size, particularly for reproductive analyses, the Lm₅₀ estimation was performed using standard logistic regression and provides preliminary information on the reproductive characteristics of this population. These findings are expected to contribute to future studies on the reproductive biology of this species in Central Kalimantan.

Evaluating the performance of the fishing gear used in this study is important. Both Tempirai and Lukah are easily deployed within the vegetated areas, unlike Lunta. These traps utilize a funnel-like entrance to guide fish inward, making escape difficult. However, a major concern is potential bycatch, including juveniles and non-target species. This issue demands immediate attention and requires effective solutions [24]. In contrast, operating Lunta requires considerable skill and experience during casting and catch handling, unlike the traps. Additional effort is often needed when the net-bag accumulates debris and mud, or becomes entangled in submerged vegetation. Lunta can be operated from either the riverbank or a small boat. The number of fish captured depends on factors such as net opening area, coverage range, and the net’s sinking and closing speed during retrieval.

Conversely, the catch efficiency of Tempirai and Lukah is constrained by the shape, size, and number of trap entrances. Fish captured by Lunta generally remain alive because the net is retrieved approximately every 10 min during operation. In contrast, Tempirai and Lukah are deployed for longer periods (hours or overnight), which may increase the risk of predation (e.g., by snakehead or otter) or natural mortality caused by stress or exhaustion. This may occur despite providing space within the traps for fish to access air. Therefore, regular cleaning and inspection are crucial to prevent deterioration of both the catch and the gear. Similar observations have been reported in previous studies [22,23].

Although differences in size distribution among captured fish may partially reflect gear selectivity, the present study did not directly assess changes in reproductive behavior or life-history strategy associated with fishing pressure. Therefore, interpret the observed patterns with caution and primarily as biological characteristics of the sampled population. Future studies in this species should focus on collecting reproductive data on female fish, in addition to total length and body weight, from a much larger number of fish. The GSI along with body weight and length traits could reveal information that can ultimately help in the management of local fish populations to ensure that the livelihoods of fishers are well protected.

To better understand the potential effects of size-selective fishing on T. pectoralis, future studies should examine fishing-gear selectivity, as different gear types may target specific size classes. Additionally, estimating growth and mortality rates across different size groups could improve understanding of population dynamics. Such information is important for evaluating the biological and ecological impacts of fishing pressure on this species.

The findings of this study have broader implications beyond biological assessment, particularly for sustainable development in wetland-dependent communities. The estimated length at first maturity (Lm₅₀), which was lower than the length at first capture (Lc₅₀) suggests that most individuals reproduce before capture, potentially supporting natural stock replenishment and ecological sustainability. This condition is particularly important for local economic stability, as small-scale fisheries remain a key source of income and food for surrounding communities [20]. In addition, the continued use of traditional fishing gear reflects low-cost, socially embedded livelihood strategies that may contribute to community resilience [23].

Nevertheless, the relatively small body size and negative allometric growth observed in this study may indicate environmental limitations or increasing ecological pressures, underscoring the need for adaptive fisheries management. Management measures such as size-based regulations, improved gear selectivity, and participatory governance could help maintain both ecological balance and equitable access to resources [44-46]. Given the dependence of local communities on small-scale inland fisheries, management strategies should also involve collaborative approaches that incorporate local fishing practices and community-based resource management. Furthermore, regional variation in biological parameters emphasizes the importance of locally adapted, ecosystem-based management approaches [47,48]. Beyond its biological significance, the present study also has socio-economic relevance for wetland-dependent communities in Central Kalimantan, where small-scale inland fisheries contribute to local livelihoods and food security [49,50]. Therefore, integrating biological information into effective fisheries management practices is important to support the long-term sustainability of inland fisheries and their contribution to environmental, economic, and social development in Southeast Asia.

T. pectoralis exhibited negative allometric growth and reached sexual maturity at a smaller size than its length at first capture, indicating that most individuals are likely able to reproduce before being harvested. These findings suggest that current fishing practices may still support population sustainability. From a management perspective, optimizing gear selectivity and evaluating growth and mortality are essential to maintain population stability. In addition, the present study has potential socio-economic relevance for wetland-dependent communities in Central Kalimantan, where T. pectoralis fisheries may support local livelihoods and contribute to food security. Therefore, integrating biological indicators with socio-economic considerations is critical to support sustainable fisheries that contribute to food security, local livelihoods, and the long-term resilience of wetland ecosystems.

Conceptualization, methodology, software, visualization, writing-original draft preparation, writing-review and editing: A.; Data curation, data collection and measurement, visualization: Z.A.I.; Validation, supervision, and investigation: I. All authors have read and agreed to the published version of the manuscript.

All summary data supporting this study’s findings, including descriptive statistics, length–weight relationship parameters, condition factor estimates, and length-at-first-maturity and length-at-first-capture values, are presented in the manuscript’s tables and figures. The raw specimen-level dataset (individual total length, body weight, sex, and fishing gear used for all 164 specimens) generated during this study is available from the corresponding author upon reasonable request.

The authors declare no conflicts of interest.

The study did not receive any external funding and was conducted using only institutional resources.

The authors gratefully acknowledge Mr. Sahid, a local fisherman, for his assistance during field sampling. The authors also sincerely thank the reviewers for their valuable comments, which significantly improved the quality of the manuscript.

During the preparation of this manuscript, the authors used ChatGPT solely for language refinement and clarity enhancement. The authors critically reviewed and edited all outputs. The authors take full responsibility for the integrity and accuracy of the work.

This study was exempt from institutional animal ethics committee review because it involved no experimental manipulation, invasive procedures, or intervention in live animals. All T. pectoralis specimens were obtained from routine, pre-existing fishing activities conducted by local fishermen using traditional fishing gear (Tempirai, Lunta, and Lukah), independent of and unaltered by the research protocol. Researchers subsequently took non-invasive external measurements (total length and body weight) of the captured specimens; no experimental treatment, dissection, or handling of live fish specifically for research purposes was conducted. As the research was limited to non-invasive measurement of a pre-existing catch unrelated to the research, formal ethics committee approval was not required under standard institutional criteria for animal research exemption.

The research was conducted and reported in accordance with the ARRIVE guidelines. The study involved fish specimens obtained from routine fishing activities and did not involve experimental manipulation or research-specific intervention in live animals.