The longfin yellowtail ( Seriola rivoliana ) is a fast-growing marine fish with high aquaculture potential . However, early larval mortality remains a bottleneck for large-scale production. This study aimed to describe the allometric growth patterns of S. rivoliana from hatching to early juvenile stages (0–30 days post-hatching, DPH) under controlled hatchery conditions. The analysis focused on the ontogenetic development of morphometric traits to identify inflection points (IPs) and support improved rearing protocols.
Larval were obtained from spontaneous spawning of domesticated broodstock at CENAIM (Ecuador). Rearing was conducted under stable physicochemical conditions with live feed and progressive weaning. A total of 620 specimens were sampled and grouped into five developmental stages. Morphometric measurements included total length (TL) and six body traits: head length (HL), eye diameter (ED), mouth length (ML), body depth (BD), trunk length (TRL), and tail length (TAL). Growth relationships were analyzed using power functions and log-transformed linear regressions. Inflection points were identified by comparing regression slopes via paired t-tests.
Growth in TL followed an exponential pattern (TL = 2.316e0.083DPH ; r2=0.99) with a specific growth rate of 8.3% per day. Early stages showed rapid morphogenesis of the head, eyes, mouth, and body depth, essential for exogenous feeding, sensory development, and locomotion. All traits displayed biphasic allometric growth with significant changes in growth coefficients before and after the IPs, ranging from 5.22 to 8.69 mm TL. After the IPs, growth patterns shifted toward isometry or negative allometry (Figure 1) . The early development of S. rivoliana is governed by biphasic allometric growth patterns.
The prioritized growth of feeding, sensory and locomotor structures before 8.69 mm TL underscores an adaptive strategy for survival under environmental pressure. The insights contribute to the biological understanding of the species and provide applied value for the refinement of larviculture protocols.