Table 1_Ontogenetic development and allometric growth patterns of the Peruvian rock seabass Paralabrax humeralis (Valenciennes, 1828) under culture conditions in Northern Chile.docx

Larval development in marine fish is a critical phase for aquaculture, as morphological and physiological changes during early ontogeny largely determine survival and subsequent performance. Paralabrax humeralis, a serranid species from the southeastern Pacific, has potential for aquaculture diversification in northern Chile; however, information on its early developmental biology and allometric growth under culture conditions remains limited. Larvae were obtained from spontaneous spawning of broodstock and reared under semi-intensive production system conditions. From hatching to 35 days post-hatching (DPH), 10–18 larvae were sampled daily and measured for total length and multiple morphometric variables related to feeding and locomotion. Developmental stages were identified following standard larval classifications, and allometric growth patterns were analyzed using power regression models. Growth trajectories were explored using LOESS smoothing, and inflection points were estimated through slope comparison analyses. Five developmental stages were identified: yolk sac, preflexion, flexion, postflexion, and early juvenile. Early development showed pronounced positive allometric growth in head and tail-related structures, reflecting functional prioritization of feeding and swimming. During flexion, growth coefficients shifted, indicating changes in developmental priorities. In postflexion and juvenile stages, most body proportions exhibited a trend toward isometric growth. Inflection points in body proportion growth were detected between 7.99 and 8.73 mm total length. The overall specific growth rate was 7.2% day-1. The observed allometric patterns indicate distinct ontogenetic growth priorities associated with key functional transitions during early development. These findings establish a morphological baseline for P. humeralis and provide essential information for optimizing larviculture protocols, supporting its incorporation into aquaculture systems in northern Chile.

海洋鱼类幼体发育是水产养殖的关键阶段，因其早期个体发生（ontogeny）过程中的形态与生理变化，在很大程度上决定了幼体的存活率及其后续生长表现。产自东南太平洋的鮨科（Serranidae）物种肩带副鲈（Paralabrax humeralis），具备在智利北部开展水产养殖品种多元化的潜力；然而目前关于该物种在养殖条件下的早期发育生物学特征与异速生长（allometric growth）规律的相关研究仍较为匮乏。实验所用幼体取自亲鱼自然产卵所获的受精卵，随后在半精养生产系统环境中进行培育。自孵化至孵化后35天（days post-hatching, DPH），每日采集10~18尾幼体，测量其全长以及与摄食、运动相关的多项形态学参数。参照通用的鱼类幼体发育阶段分类标准对其发育时期进行划分，并通过幂回归（power regression）模型分析异速生长模式。采用局部加权回归散点平滑法（LOESS smoothing）探究生长轨迹，并通过斜率比较分析估算生长拐点。本次实验共划分出5个幼体发育阶段：卵黄囊期（yolk sac）、前弯曲期（preflexion）、弯曲期（flexion）、后弯曲期（postflexion）以及早期稚鱼期（early juvenile）。早期发育阶段，头部与尾部相关结构呈现显著的正异速生长，反映出该物种对摄食与游泳功能的发育优先级。在弯曲期阶段，生长系数发生改变，表明其发育优先级出现调整。进入后弯曲期与稚鱼期后，多数身体比例呈现等距生长（isometric growth）的趋势。身体比例生长的拐点出现在全长7.99~8.73 mm的区间内。整体的比生长速率为7.2%/天。本次观测到的异速生长模式，反映了该物种早期发育过程中与关键功能转型相关的独特个体发生生长优先级。本研究结果为肩带副鲈（P. humeralis）建立了形态学基准数据，并为优化其幼体培育规程提供了关键参考依据，有助于推动该物种在智利北部水产养殖体系中的应用。