Resumen del producto

The Dolphinfish, Coryphaena hippurus, is an epipelagic predator that inhabits temperate and tropical seas worldwide. In the Eastern Pacific Ocean (EPO) it ranges from 46°N to 38°S, where it is captured either incidentally or as a target species. Given its migratory nature, setting management measures requires to determine whether the fishing operations in EPO are affecting just a single or more than one stock. Genetic investigations conducted to date have been inconclusive in this regard, as a high genetic variability has been observed. In recent years, the use of otolith morphometry has allowed the identification of stocks of various fish species; thus, this study describes the morphometry of the sagitta otolith for different Dolphinfish sizes caught off Cabo San Lucas, Mexico. If the morphometry of these calcified structures is an adaptive result of a specific environment-related and life-history trait, then the environmental spatial heterogeneity and differences in population dynamics across EPO may affect the phenotypic characteristics of this bone and, ultimately, we may have a tool to discriminate between stocks. Nevertheless, to determine whether this tool is suitable to discriminate between stocks, fish samples collected throughout EPO and analyzed under a comparative approach are needed. In this work, the morphometric description is based on samples collected between January 2007 and December 2014. For each fish, fork length, weight and sex were recorded. The left sagitta otolith of each specimen was photographed, and the perimeter, area, length and width of each otolith were measured and recorded. Otolith contours were detected by transformation of grayscale images; in order to obtain automatic layouts, these were transformed to binary data using a threshold pixel value (intensity threshold). Otolith contours were reconstructed using Fourier coefficients (FC) through a Fourier’s elliptical analysis. To assess the morphology pattern of otoliths between interval sizes and sexes, a principal component analysis was used with the FC data matrix, which was also applied to reduce data size. Otolith samples were compared between interval sizes and sexes using multivariate analysis of variance and canonical discriminant analyses. The results show that the main variation in otolith shape is observed in two specific otolith features: the point of separation between the rostrum and antirostrum, and the posterior separation of dorsal and ventral otolith wings.

Palabras clave: Otoliths; morphometric; Dolphinfish

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