Otolith Sr/Ca reveals ontogenetic shifts in the leopard coral grouper Plectropomus leopardus

The coral grouper Plectropomus leopardus holds significant economic importance in the live grouper fish trade of the Indo-West Pacific region, yet its developmental and life-history patterns remain poorly understood. Here, we analyzed otolith core-to-edge Sr/Ca of P. leopardus individuals from 4 Philippine localities (Linapacan, Quezon, and Taytay in Palawan, and Tawi-Tawi) using laser ablation inductively coupled plasma mass spectrometry to infer ontogenetic shifts. Otolith core-to-edge transects had Sr/Ca ranging from 1.47 to 3.83 mmol mol -1 and exhibited consistent U-shaped patterns: elevated early-life values; declining values during the potential juvenile and small adult period; and gradual increases during later life stages. Functional principal component analysis identified 2 distinct ontogenetic profiles: (1) early transitioners with shifts within the first year, and (2) late transitioners with delayed shifts at approximately 3 years of age. The relative frequency of these ontogenetic patterns in Sr/Ca varied among sites, with early transitioners dominating in Quezon (~80%) and late transitioners in Linapacan, Taytay, and Tawi-Tawi (>70%). Within late transitioners, individuals from Tawi-Tawi had higher mean Sr/Ca than those from Linapacan and Taytay, indicating regional differences in Sr incorporation. These findings reveal intra-population life-history diversity and regional variation in ontogeny, possibly related to resource partitioning to reduce intraspecific competition. Such variability underscores the importance of multiple life-history strategies to sustain recruitment and long-term population resilience in coral reef fishes.