During the winter months, seasonal winds blow through gaps in the mountain ranges, pushing the surface waters offshore. This causes deep, oxygen-poor water to upwell, and the thermocline is very shallow. Small, prey species are restricted to the oxygenated waters above the thermocline, and predators like billfish and tuna follow. This "habitat compression" means that the fish apend most of their time very close to the surface, and is responsible for the high catch rates in the region.

 

In our lab at the University of Miami, we are engaged in a tagging program to exhamine the migrations and depth residency of sailfish and marlin. The Billfish Research Center is studying the billfish's use of oceanographic retention mechanisms like seasonal eddies for feeding and spawning.