The Norht Pacific SubTropical Front
(STF) is marked by the 18°C SST isotherm
and the Transition Zone Chlorophyll Front
(TZCF) by the 0.2 mg chl.m-3
isopleth. They roughly mark the northern boundary of the North Pacific Subtropical
Gyre as well as the northern extent of the Hawai`i-permitted longline fishery. The
STF is targeted by the swordfish fishery. Additionally, both the STF and TZCF are used
as migration and foraging corridors by both commercially-valuable and protected species.
Both fronts migrate meridionally seasonally and their positions are impacted by the phase
of ENSO. Due to significant seasonal variation, the climatology
(SST: 1982 – 2015, Chl: 2003 – 2015) and anomaly (2016) are presented for the first quarter
of the year only, when the swordfish fishery operates.
The climatological (solid) and 2016 (dashed) positions of the STF (red) and
TZCF (blue) in the first quarter of the year (Jan – Mar).