Landmark-based geometric morphometric and meristic analysis of body shape variation among Indonesian climbing perch <i>Anabas testudineus</i> (Bloch, 1792) populations

Fish stock assessments require a holistic approach that accounts for population heterogeneity, size range, sampling time frames, and habitat characteristics. However, these theoretical principles are often overlooked, potentially resulting in inappropriate fishery management decisions. This research aimed to evaluate (1) the spatial variation in the morphology of climbing perch (Anabas testudineus) across Indonesian populations using truss network analysis and (2) the temporal stability of these morphological traits over 90 years, assessed at 10-year intervals in habitats with varying ecological characteristics. The study analyzed 235 fish specimens from 20 Indonesian provinces, preserved at the Museum Zoologicum Bogoriense (MZB), Cibinong, Indonesia. Morphometric data were collected using the truss network method, measuring 19 distances between 10 anatomical landmarks with digital calipers. Nine meristic traits were recorded, including scale and fin spine/ray counts. Morphometric traits were standardized and analyzed using bivariate and multivariate statistical techniques. Based on the results of this study, population heterogeneity and the sampling time frame showed minimal influence on phenotypic variation, with a tendency for overlap between groups. Discrimination was observed among three islands – Sumatra, Kalimantan, and Sumba (with differences ranging from 2.1 to 2.39 mm) – as well as between the sampling periods <1970 and 1970–1980, with differences reaching up to 2.47 mm, and between the periods <1970 and 1980–1990, with a recorded difference of 2.36 mm. However, population and habitat characteristics had a significant effect on morphotype. Body depth and caudal peduncle shape significantly contributed to between-sub-population heterogeneity, while habitat characteristics were associated with all three body regions. These results demonstrate that the morphometric truss method can comprehensively evaluate fish population structure, with implications for decision-making to support sustainable fisheries management.