Molecular identification of genetic variants of Neocalanus flemingeri in the Gulf of Alaska from samples collected from 2015 to 2023

The subarctic Pacific is inhabit by three copepod congeners in the genus Neocalanus with an overlapping biogeographic range that includes the open ocean, marginal seas and fjord systems. Two distinct genetic variants of Neocalanus flemingeri have been reported from the western Pacific: the “small form” with an annual life cycle is found throughout the region, while the “large form” population with a 2-year life cycle is centered in the Sea of Okhotsk. Using a molecular approach, this study examined the genetic composition of N. flemingeri populations in the Gulf of Alaska from multiple stations over an eight-year period using existing nucleotide sequence data from RNA-Seq, Sanger sequencing and metabarcoding data. This is the first report for the occurrence of the large form in the eastern Pacific with a significant presence in fjord systems.