Morphometrics and meristics variation of Uroteuthis chinensis in the north coast waters of Central Java, Indonesia

Uroteuthis chinensis (mitre squid) is a commercially important cephalopod species in Indonesian waters, particularly along the north coast of Central Java. Understanding its morphological variation is essential for stock identification and sustainable fisheries management. This study aimed to analyze the morphometric and meristic characteristics of U. chinensis collected from Rembang and Tegal waters. A total of 224 specimens were examined (109 from Rembang and 115 from Tegal) using 19 morphometric characters and two meristic characters (number of sucker ring teeth on the tentacles and third arms). The Shapiro-Wilk test, Whitney U test, Principal Component Analysis (PCA), and Spearman’s correlation were performed to analyze morphometric and meristic variation and relationship. Whitney U test indicated significant differences (p < 0.05) in most morphometric characters between populations, especially in mantle, fin, and arm dimensions. The PCA extracted three principal components that cumulatively explained 71.2% of the total variance. Left fin length, mantle length, and head width were identified as the most significant contributors to morphological differentiation. However, PCA scatterplots displayed overlapping clusters between Rembang and Tegal, suggesting limited morphological divergence. Spearman’s correlation indicated that certain morphometric traits, particularly fin length, tentacle length, and total length, were strongly correlated with mantle length (p > 0.7), especially in the Rembang population. In contrast, the Tegal population showed weaker correlations, with only fin length showing a strong relationship. These findings suggest, that although U. chinensis populations from both sites likely belong to the same biological stock, some degree of morphometric variation exists, possibly due to environmental or ecological factors. The study underscores the importance of combining morphometric and meristic analyses to support effective stock identification and the sustainable management of squid fisheries in Indonesia.