Molecular identification of pelagic fish eggs with oil globule

Marine fish eggs exhibit transversal morphological characteristics that complicate their identification. It is estimated that 75% of pelagic eggs possess oil globule(s). Identifying these eggs provides valuable information about spawning biomass and potential spawning areas for commercially important and threatened species. Molecular markers, such as the FISH (COI gene), enable a precise identification and exploration of the genetic variability within fish populations. San Vicente Bay, located in south-central Chile is partially protected from the effects of the Humboldt current, making it a notable spawning and nursery ground for various fish species. This study aims to identify and characterize, oil-globule-containing eggs present in the bay during October, a period that aligns with the spawning season of many species.

This study seek to standardize the DNA extraction method and PCR process, addressing the challenges posed by the low quantities of tissue in these eggs. We employed 2 methods, by a DNA extraction kit and Chelex resin. Out of 94 eggs, 24 samples yielded positive PCR results, corresponding to a 25% of success. All these eggs were successfully identified using genetic databases, revealing a total of 9 genera and 8 species. The observed genetic distances at the species level were low, supporting the hypothesis that the eggs originated from the same female or gene mutation rate.

The methods employed successfully identified fish eggs and documented species whose early life stages have not been previously reported in the bay.