Introduction: Wetlands are among the most important and productive ecosystems on Earth, playing a vital role in biodiversity conservation and providing various environmental and economic benefits, including water purification, flood regulation, and recreational services. Effective conservation of these ecosystems requires a thorough understanding of their biological components, particularly aquatic species such as fish, whose biogeography and biology are still poorly understood. Anzali Wetland, one of Iran’s key freshwater habitats, has high ecological and economic importance due to its unique geographic location and direct connection to the Caspian Sea. It supports diverse plant and animal species, particularly fish, which are crucial for ecological balance. Among them, Hemiculter leucisculus is a key species recognized for its adaptability to diverse environmental conditions. Studying its growth, feeding, and reproductive traits provides valuable information on habitat quality, environmental impacts, and sustainable ecosystem management. Biological indices such as length–weight relationships, gonad weight, condition factor, gonadosomatic index, and length–age distribution are essential tools for understanding fish biology and population dynamics. This study aims to analyze the biological and reproductive indices of Sharpbelly in Anzali Wetland, examining seasonal and spatial patterns to provide a comprehensive understanding of the species’ biology and support wetland biodiversity conservation.
Materials and Method: Sampling of Sharpbelly (Hemiculter leucisculus) in Anzali Wetland was conducted across three stations (eastern, central, and western) during all four seasons of 2021 to examine seasonal and spatial variations in biological traits. A total of 130 specimens were collected using electroshockers and cast nets during early morning hours and transferred to the laboratory for analysis.
For each fish, total length (TL), body weight (W), and age (A) were recorded. Length was measured with 0.1 mm accuracy, weight with 0.01 g precision, and age was determined via growth rings on scales. These data were used to investigate biological patterns across stations and seasons.
Key indices—including gonad weight (GW), condition factor (CF), and gonadosomatic ratio (GSR)—were calculated to assess nutritional status and sexual maturity. Data analysis was performed in SPSS 26. One-way ANOVA and Tukey’s post-hoc test were applied to compare indices among stations and seasons, and growth patterns were evaluated using Pauly’s method.
Results and Discussion: The biological and physiological characteristics of Hemiculter leucisculus in Anzali Wetland showed notable variation across sexes, stations, and seasons. Total length (TL) ranged from 4.3 to 16.4 cm (mean 11.3 ± 3.3 cm) and body weight (W) from 0.52 to 30 g (mean 12.4 ± 9.2 g). Males and females had similar mean lengths (11.3 cm and 11.4 cm) and weights (11.8 g and 13.1 g), but females had higher gonad weights (0.7 g vs. 0.13 g), indicating greater reproductive investment. Condition factor (K) was comparable between sexes, while gonadosomatic ratio (GSR) was consistently higher in females, particularly at the central station. Spatial analysis revealed allometric growth in all stations, with length–weight coefficients (b) and high R² values confirming robust models. Length-frequency distributions indicated that females at the central station dominated larger size classes (12–16 cm), whereas males in the western station were more abundant in smaller size classes (6–8 cm). Seasonal age patterns showed higher abundances of young fish (0–1 year) in summer and winter, while older fish (3–6 years) appeared mainly in spring and summer, suggesting seasonal recruitment and survival trends. Growth analysis demonstrated increasing TL and W with age, though growth rates varied spatially. Polynomial regression models indicated slower growth in the western station but with more predictable patterns. Overall, H. leucisculus exhibits significant spatial and seasonal variability in growth, reproductive indices, and condition, highlighting the importance of incorporating temporal and spatial factors in wetland fish management and conservation.
Conclusion: This study examined the biological and physiological characteristics of Hemiculter leucisculus in Anzali Wetland, focusing on total length, body weight, age, gonad weight, condition factor (K), and gonadosomatic ratio (GSR). Results showed that these traits are influenced by habitat, sex, and age. Total length ranged from 4.3 to 16.4 cm and body weight from 0.52 to 30 g, with mean values of 11.3 cm and 12.4 g, reflecting high morphological diversity. Age distribution spanned 0–6 years, with two-year-old fish dominating, while condition factor values indicated good nutritional status. Females exhibited higher GSR, highlighting greater reproductive investment. Length–weight relationships indicated allometric growth, and spatial variations among stations suggested habitat quality and food availability affect growth and reproduction. The findings emphasize the need for future studies with larger, more frequent sampling across multiple habitats to capture seasonal and annual variations. Evaluating environmental factors such as water quality, climate change, and anthropogenic pressures, along with implementing monitoring and management programs to reduce human impacts and enhance habitat conditions, is essential for the sustainable conservation of this ecologically important species.
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