Abstract
Associations between ocean surface thermal fronts and the swordfish catch rates of U.S. longline vessels were explored. The study area was the western North Atlantic off the United States, extending from 32°N to 45°N and from 76°W to 63°W. To locate and describe fronts, we used three variables computed from satellite-derived sea surface temperature (SST): horizontal gradient, distance to nearest thermal surface front, and frontal density. Most of the fishing effort analysed occurred along the edge of the continental shelf, where there was a high frequency of frontal presence. Very high catch per unit effort (CPUE) occurred more frequently in the vicinity of fronts than would be expected by chance. The high variability of CPUE that could not be explained by our frontal parameters suggested other, unmeasured, factors also influenced catch rates.
