Effects of oceanography on North Pacific armorhead recruitment in the Emperor Seamounts

The North Pacific armorhead (NPA), Pentaceros wheeleri, is thought to exhibit an extended post-spawning epipelagic phase in which larvae disperse to the northeast Pacific Ocean. Current understanding of juvenile distribution, development, and mechanisms that drive recruitment variation, however, remains largely incomplete. The objective of this study was to compare a time series of NPA recruitment to established climate indices and to environmental covariates to explore drivers of the NPA life cycle. Additionally, this work investigates potential larval NPA transport pathways and their positional relationships to the proposed northeastern nursery grounds. Using Lagrangian particle tracking, trajectories of passive larvae were simulated at depths of 0 and 15 m for 18 years (2001–2018) from the Southern Emperor-Northern Hawaiian Ridge (SE-NHR) natal habitat. Dispersal distances and particle end positions were examined for their potential relationships with recruitment. Sea surface temperature and net primary productivity were evaluated as predictor variables using generalized additive modeling. Neither regression of particle end-point characteristics nor environmental covariates resulted in significant correlations with recruitment here, perhaps owing to data limitations surrounding the nursery zone. Particles were found to be advected largely within the North Pacific transition zone in the central north Pacific. Significant seasonal correlations were found between recruitment and the Arctic Oscillation, Pacific Decadal Oscillation and North Pacific Gyre Oscillation, suggesting that NPA recruitment mechanisms respond to interannual ocean-atmospheric climate oscillations. Better knowledge of the connections between recruitment and the environment would be valuable for stock management, and improvements for advection predictions are discussed.