Reproduction of Mitre squid, Uroteuthis chinensis, in Okinawa

Despite the importance of Mitre squid, Uroteuthis chinensis, as a fishery resource in the Western Pacific, there have been limited research conducted on their biology. Here, we present observational evidence of U. chinensis’s reproduction in the coastal waters of Okinawa over multiple years. We found nesting events where a female laid nearly 100 eggs per single string, and we found egg masses exceeding 100 strings on the monitored site that produced far over 40,000 viable hatchlings in the October–November season of 2021. Egg capsules with expanded chorion averaged 7.23 ± 0.75 mm in diameter. The oocytes had some variation in their long and short diameters, measuring at 1.24 ± 0.13 and 0.82 ± 0.10 mm respectively. The eggs were incubated for two weeks after their collection and successfully hatched. We sequenced the entire genome and associated metagenome of one hatchling, and we described the complete mitochondrial genome of U. chinensis from Okinawa. All DNA sequencing data are available at NCBI Genbank PRJNA1285506. The mitogenome is 17,389 bp in length, encoding the standard set of 13 protein-coding genes and 2 RNA genes with circular organization. COI haplotype network delivers robust evidence that this species forms a single large, interconnected population in the Western Pacific Ocean. This study provides important information about the reproductive capabilities of U. chinensis in changing marine environments, which is necessary for the sustainable management of fisheries resources.