A sex-specific molecular marker in Mulloway (Argyrosomus japonicus)

Mulloway (Argyrosomus japonicus) is an endangered species. Dwindling fisheries have prompted restocking efforts. Discerning the sex of Mulloway, crucial for effective aquaculture and conservation, is difficult due to the lack of phenotypical indicators. This study reports the development of reliable PCR-based sex identification markers in Mulloway, providing a rapid and effective tool for accurately determining the sex of non-spawning Mulloway of all ages. The pipeline employed in this study demonstrates a straight-forward method for biodiscovery of sex markers in species with poor genomic resources. This has applications in aquaculture management and wild sampling, as well as in understanding life history and sex determination strategies for this endangered species. Sex markers were developed via Whole Genome Sequencing together with targeted bioinformatics and are based on the dmrt1 gene, specifically a 95 bp deletion in the male sequence of dmrt1. DNA samples from thirty-one known-sex, wild-caught adult Mulloway were used to confirm the accuracy and reliability of the sex markers in distinguishing between male and female individuals. Following this, markers were used to identify the genetic sex of juvenile fish which were then validated by histological examination of gonads. The sex markers were found to be consistent with observed sex in all cases. These markers, validated on both adult broodstock and juveniles, offer a reliable and efficient means of sex determination, contributing to the optimisation of breeding programs and sustainable management of Mulloway. The identification of the 95 bp deletion in the male sequence of dmrt1 increases understanding of Mulloway sex determination, the application extends beyond aquaculture management, offering insights into the life history and molecular mechanism underlying sex determination in this endangered species.