Lapillus otolith shape, a useful taxonomic feature for the identification of sea catfishes (Ariidae: Siluriformes) from the north-eastern Pacific.

Otolith shape is widely used as a taxonomic feature in fish systematics. In Siluriformes, the lapillus otolith is the most relevant character for taxonomic purposes, although its discriminant potential has not been assessed quantitatively. Our study model were sea catfishes of the family Ariidae from the north-eastern Pacific as representatives of Siluriformes, a taxon with increased taxonomic complexity. The lapillus otolith shape obtained by geometric morphometrics showed high discrimination potential both at the genus and species levels with an overall classification accuracy of c. 93% (K = 0.92). Due to the strong species delimitation exhibited by lapillus otolith shape, the descriptions and identification keys provided here are the most useful materials to recognize the eight sea catfish species evaluated. The shared similarities in lapillus otolith shape among species seem to be more influenced by phylogenetic relationships than other factors such as habitat. The lapillus otolith shape is the most powerful taxonomic feature discovered so far for the identification of sea catfishes from the north-eastern Pacific.

Genetic diversity, population structure, and demographic history of the chilhuil sea catfish Bagre panamensis in Northwestern Mexico inferred from mitochondrial DNA.

The chilhuil sea catfish (Bagre panamensis) is an ecologically relevant species contributing to the structure, organization, and functioning of the ecosystems it inhabits. Also, it is an important artisanal fishery resource in the Mexican Pacific coast. This study aimed to determine the genetic diversity, population structure, and historical demography of B. panamensis in the Mexican Pacific. The mitochondrial DNA was amplified from two distinct regions, r16S and COI, resulting in an 1142 bp of the concatenated genes. Low genetic diversity levels were detected for r16S (H = 12; h = 0.131; π = 0.0003) and high genetic diversity levels for COI (H = 57; h = 0.9128; π = 0.0039) and the concatenated gene fragments (H = 62; h = 0.9307; π = 0.0023). Population structure analysis indicated 'panmixia' for B. panamensis along the Mexican Pacific. Furthermore, historical demographic analysis (Tajima's D, Fu's Fs, mismatch distribution, and Bayesian Skyline plot analyses) supported a population expansion scenario for the studied species.