Jurnal Iktiologi Indonesia

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. . — 2026-06-01

Morphometric Relationship of Otolith With Body Length and Weight of Bonylip Barb (Osteochilus Vittatus Valenciennes, 1842) in The Rivers of Magelang Regency

Nurul Azizah Puteri Rahma Dewi — 2026-10-22

The bonylip barb (Osteochilus vittatus) is a freshwater fish species commonly found in the rivers of Magelang Regency and is captured by the fishermen as a source of protein. The purpose of this study is to determine the relationship between the morphometric and the somatic body size of the bonylip barb. Samples were collected from the catch of fishermen in the river waters of Magelang Regency from September to December 2025. The total number of fish samples used in this study was 105 individuals (62 male fish and 43 female fish). The fish body was measured for length and weight, then dissected, and the otolith was removed for otolith morphometric measurements (otolith length, width, area, perimeter, and mass). Morphometric parameters of otoliths were measured using ImageJ, and otoliths were weighed on an analytical balance. The results of the otolith shape index analysis of bonylip barb, based on otolith morphometrics, indicate that oval-shaped otoliths tend to be elongated and irregularly surfaced. The relationships between male and female otoliths and between right and left otoliths were tested separately using t-tests. Statistical analysis of otoliths by gender showed no significant differences in length, width, or area, whereas circumference and weight differed significantly. The statistical test of the right and left otoliths showed no significant differences in any otolith parameters, indicating that the otoliths are symmetrical. The relationship between the length and weight of the bony lip barb is reflected in the linear regression equation y(i) = a + bx. The analysis results show a positive relationship between fish somatic size and otolith size, indicating that the otolith can serve as an indicator of fish growth.

Feeding Habits of Sergang Fish (Ambassis Interrupta) in The Cengkrong Tidal Creek, Trenggalek, East Java

Titis Dwi Andhani — 2026-10-22

Estuarine ecosystems provide a diverse range of natural food sources for fish, reflecting the dynamics of trophic interactions in these waters. In estuarine species such as the sergang fish (Ambassis interrupta), diet composition can be used to determine the fish’s trophic position within the food chain. This study aims to analyze the diet composition and feeding patterns of the sergang fish using the Relative Gut Length (RGL) parameter, diet composition, and the Index of Stomach Content (ISC). Fish stomach samples were collected directly in the field and preserved using 10% NBF for dietary composition analysis, while gut length was measured to determine food groups. The results showed RGL values ranging from 0.57–0.71% (omnivorous) and ISC values ranging from 0.25 – 1.09% (active foragers). The dietary composition of the sergang fish consisted of 62% phytoplankton (12 genera) and 38% zooplankton (5 genera). Based on the RGL value, the sergang fish belongs to the omnivorous group, however, the dietary composition indicates that this fish is classified as a plankton feeder, with a preference for phytoplankton. This indicates that feeding patterns are strongly influenced by food availability, with phytoplankton serving as the primary food source. This feeding pattern positions the sergang fish as a link between primary producers and higher-level consumers, making its population crucial for maintaining the stability of the food chain. To preserve ecosystem balance, an integrated approach is necessary to prevent environmental changes and ensure that the fish’s feeding patterns and habits remain undisturbed.

Species Composition and Temporal Patterns of Upstream-Migrating Fish at Kamijoro Weir, Yogyakarta, Indonesia

Ainun Ainun Nurhayati — 2026-10-22

This study aimed to identify species composition, analyze temporal migration patterns, and assess gonad maturity stages of upstream-migrating fish at the Kamijoro Dam on the Lower Progo River, Yogyakarta. We conducted the research over five months (September 2025–January 2026) using a hanging fish trap net installed at the dam, with morning and afternoon sampling. We identified each specimen, measured its total length and weight, and assigned a gonad maturity stage (GML I–V) based on descriptive criteria. We captured 1,603 individuals from seven species of the family Cyprinidae, dominated by Barbonymus schwanefeldii (42.98%) and Mystacoleucus obtusirostris (41.92%). Catch numbers peaked in October (1,028 individuals; 64.1%) and subsequently declined sharply by January (11 individuals). Most catch (81.2%) occurred in the afternoon. GML analysis revealed the following distribution: GML I (3.2%), II (48.9%), III (22.3%), IV (23.4%), and V (2.1%). The dominance of immature fish (GML II–III = 71.2%) suggests that the migration was primarily driven by foraging, whereas the presence of sexually mature fish (GML IV = 23.4%)—specifically among Osteochilus vittatus (56.5%) and Labiobarbus leptocheilus (58.3%)—indicates the occurrence of reproductive migration. The afternoon catch bias reflects circadian rhythms, while the exclusive presence of Cyprinidae suggests community simplification resulting from the weir's influence. The study concludes that the Kamijoro Weir serves as a critical aggregation point for migratory fish exhibiting distinct temporal patterns, highlighting the need for sustainable fisheries management and long-term monitoring.

Assessing Fish Diversity, Water Quality, and Conservation Evidence in Mahakam Fish in the Tropical Rainforest Environment (Book Review)

Lenny S Syafei — 2026-10-22

Fish biodiversity is a key indicator of aquatic ecosystem health and sustainable freshwater management, particularly in the diverse but increasingly pressured Mahakam River system. Mahakam Fish in the Tropical Rainforest Environment provides field-based information on fish biodiversity and aquatic environmental conditions. This review critically evaluates evidence on fish biodiversity, water quality, and fish conservation. A descriptive-analytical critical review was conducted based on sampling design, study coverage, data collection, and consistency of findings and recommendations. The study covered the Kedang Kepala River, Kedang Rantau River, and Lake Siran using seven sampling stations. Fish diversity was assessed using Shannon–Wiener, Evenness, Dominance, and Margalef indices, while water quality was evaluated using physicochemical parameters and the Storet method. Storet results classified the Kedang Kepala River as slightly polluted, Kedang Rantau River as moderately to heavily polluted, and Lake Siran as moderately polluted. Four introduced fish species were recorded, while Chitala borneensis was not captured and Notopterus notopterus was found. The book’s broad coverage of biological and physicochemical aspects is a major strength; however, the sampling design, temporal coverage, data integration, and ecological interpretation require further consideration. Future studies should incorporate long-term monitoring to strengthen evidence-based conservation and ecosystem management.

Reproductive Biology of Indo-Pacific King Mackerel (Scomberomorus guttatus Bloch & Schneider, 1801) in Bantul Waters

Imron Thohai — 2026-10-22

This study investigated the reproductive biology of Indo-Pacific king mackerel (Scomberomorus guttatus) in Bantul waters, Yogyakarta, Indonesia, to provide baseline data for sustainable fisheries management. We collected 96 specimens (51 females, 45 males) from October 2021 to February 2022 using gillnets (3.5-inch mesh) and hook-and-line (size 12) along the Pantai Baru, Kuwaru, and Depok coasts. The sex ratio was 1:0.8 (female: male), showing no significant differences from 1:1 (chi2 = 0.75, p > 0.05). Gonad maturity level (GML) distribution showed that 58.8% of females were immature (GML I), while males were more advanced, with 42.2% at GML II and 13.3% at GML III. Gonadosomatic index (GSL) increased progressively from GML II to GML IV in both sexes, with females reaching 2.3±0.97% and males 0.42±0.08% at GML IV. Length and weight distributions were similar between sexes, with a modal length of 38 cm (31.4% females, 33.3% males) and a modal weight of 400 g (45.1% females, 48.9% males). Egg diameter analysis revealed two distinct populations: pre-spawning eggs (0.2-0.5 mm, 52.9%) and mature eggs (0.6-0.8 mm, 47.1%), indicating partial spawning behavior. Fecundity ranged from 60,000 to 352,000 eggs for fish measuring 45.8-55.1 cm, following a power relationship with body length. Length at first capture (Lc) was approximately 37 cm for both sexes, while length at first maturity (Lm) was estimated at 45 cm for females and 41 cm for males. These findings indicate that current fishing practices in Bantul waters capture a substantial proportion of immature individuals, particularly females, suggesting the need for management interventions including minimum size regulations and seasonal closures during peak spawning periods to ensure sustainable exploitation of this commercially important species

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. . — 2026-06-01