Draft genome sequencing and assembly of Risso's dolphin, Grampus griseus

The Risso's dolphin (Grampus griseus) is one of the migratory marine mammals and they have commonly dispersed in tropical and temperate seas. It is a least concerned species in the IUCN red list of threatened species. However, their population size and factors affecting their population structure are unknown. Due to the wide distribution of this species, their populations might be genetically stable and less structured. To support genetic studies on dolphins and other marine mammals, we assembled the draft genome of Risso's dolphin that was found in Japan. The tissue samples were used to extract high molecular DNA and subjected to sequencing by Illumina HiSeq X, Oxford Nanopore MinION, and Bionano Saphyr. The assembled hybrid genome was 75.9% of complete eukaryotic BUSCOs and the genome size was 2.256 Gb with 2.042 Mb of scaffold N50. De novo assembly of this genome by Bionano Saphyr recovered 2.036 Gb total genome map length and structural variations. The gene structures of this draft genome were identified by BRAKER2, and 9947 genes were recovered. The data will be useful for future studies of cetaceans.