Biology and morphometrics of dominant salp species in the subarctic Northeast Pacific

Salps are ubiquitous members of shelf break and offshore zooplankton communities in the subarctic Northeast Pacific. However, little is known about their species composition and biology compared to other regions in the Pacific. Seven salp species occur more or less frequently, whereas three of them numerically dominate: Cyclosalpa bakeri, Salpa aspera, and S. fusiformis. Two more southern salp taxa, Thalia democratica and Thetys vagina, not sampled since 2016, re-invaded the subarctic Northeast Pacific likely due to a series of marine heat waves. Specimens were collected during 1985–2020 using various gear types (BIONESS, Bongo net, midwater trawl, Multinet, neuston net, ring net, Tucker trawl) in the top 250 m (occasionally down to 1500 m) off the west coast of British Columbia, Canada. In total, approximately 1200 salp specimens were analysed. General salp biology, including life cycle stage and development stage compositions as well as body morphometrics (i.e., total length, oral-atrial length, embryo length, stolon properties, gut diameter) were measured. Species, size-, and stage-specific differences were compared. For the three dominant species and T. democratica, first biological and morphometric measurements in the subarctic Northeast Pacific are provided.