Improved method to investigate natal homing in marine fish with otolith chemistry

Natal homing in fish is a crucial phenomenon that shapes the ecology and evolution of populations. The homing behavior of fish has been well studied in several species. However, research has focused on a limited number of fish species due to methodological constraints, whereby the methods are either too expensive or there are too few suitable species to which they could be applied. We propose a scheme to optimize the ‘otolith edge’ concept, followed by the establishment of a discriminant model based on the optimized elemental fingerprints as natural markers. We take small yellow croaker Larimichthys polyactis (Bleeker, 1877) as an example. A 10-row by 3-column laser spot lattice on the otolith edge was identified as the optimal arrangement, and then spawning individuals from the same cohort were identified using the discriminant model. Homing rates of small yellow croakers were as follows: 86% in Haizhou Bay, 71% in Lvsi, 17% in Zhoushan, and 28% in Dachen. The results show that the otolith fingerprint as a natural marker is feasible for fish homing studies, but the application of otolith elemental fingerprints requires strictly quantitative evaluation.