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All Journal Saintek Perikanan : Indonesian Journal of Fisheries Science and Technology LIMNOTEK
Siti Rukayah
Fakultas Biologi Unsoed
Earth & Planetary Sciences Education Engineering Environmental Science

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SEASONAL VARIATIONS IN THE REPRODUCTION OF TWOSPOT CATFISH (Mystus nigriceps) FIN THE CICINGGULING RIVER, KEBUMEN, CENTRAL JAVA Siti Rukayah; Agus Nuryanto; W Lestari; Isdy Sulistyo
Saintek Perikanan : Indonesian Journal of Fisheries Science and Technology Vol 22, No 2 (2026): SAINTEK PERIKANAN
Publisher : Fakultas Perikanan dan Ilmu Kelautan, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ijfst.22.2.102-108

Abstract

The Cicingguling River in Kebumen Regency is a freshwater ecosystem that serves as a critical habitat for native fish species, including Mystus nigriceps, which holds high ecological and economic value. This study aims to examine the reproductive characteristics of M. nigriceps over a full annual cycle (November 2022 - October 2023) using a survey method with purposive sampling. Field and laboratory sampling were conducted monthly to evaluate sex ratio, gonadal maturity stage (GMS), gonadosomatic index (GSI), fecundity, and egg diameter. The results showed an unbalanced sex ratio, with the number of female fish far exceeding that of males throughout the year. The GMS III and IV were higher during the rainy season, with GMS III at 295 individuals (female) and 170 individuals (male), and GMS IV at 259 individuals (female) and 144 individuals (male). The GSI and fecundity increased from December to February, coinciding with increased rainfall. The highest GSI and fecundity were recorded in January at 12.98% (females) and 6.63% (males), with fecundity reaching 17,927 eggs, accompanied by high rainfall (403 mm). Egg diameter during the rainy season showed a single peak (0.41–0.50 mm). In conclusion, M. nigriceps exhibits a seasonal reproductive pattern, indicating that the development of aquaculture and population dynamics depend on season-based management strategies. These findings provide a biological basis for data-driven conservation and support the sustainable management of freshwater fish resources in Central Java.
Assessment of Habitat Characteristics Influencing Fish Diversity in the Ijo River, Central Java, Indonesia Siti Rukayah; Agus Nuryanto; Windiriani Lestari; M. Husein Sastranegara,
LIMNOTEK Perairan Darat Tropis di Indonesia Vol. 32 No. 1 (2026)
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/limnotek.2026.14811

Abstract

Freshwater fish populations are highly sensitive to habitat variation, yet information on how habitat characteristics shape fish diversity in Central Java rivers remains limited. The Ijo River is an important natural system for evaluating ecological factors that determine fish communities. This study aims to assess the physical and chemical characteristics of the Ijo River and evaluate their influence on fish diversity. Research was conducted using survey methods and purposive random sampling at nine stations across three zones: upstream, middle, and downstream. The results obtained are that the environmental parameters varied across river zones. The downstream zone recorded the highest temperature (29.14°C), greatest depth (2.54 m), widest channel (32.97 m), and highest free CO₂ (12.64 ppm). The upstream zone showed the greatest light penetration (74.43 cm), fastest Current Velocity (0.75 m/s), highest dissolved oxygen (5.28 ppm), and highest pH (8.31). Fish diversity also differed between zones. The downstream zone had the highest abundance (4,885 individuals) and greatest dominance (0.17), whereas the upstream zone exhibited the highest Shannon-Wiener diversity index (2.46) and evenness (0.36). These results indicate that upstream zones, with lower temperatures, faster currents, higher dissolved oxygen, and stable pH, support greater species diversity and evenness. Downstream zones, with higher temperatures, elevated free CO₂, and wider river width, show greater abundance but are dominated by a few adaptive species. This pattern, consistent with other rivers, confirms that physical and chemical water characteristics shape distribution, abundance, and dominance of freshwater fish. Thus, fish diversity is a key indicator of river ecosystem health.
Co-Authors Agus Nuryanto Agus Nuryanto Isdy Sulistyo M. Husein Sastranegara, W Lestari Windiriani Lestari