Every October, the frigid (60 - 65F), nutrient rich Humboldt Current, which flows north from Antarctica toward the Equator, (which is why there are penguins in the Galapagos) is pushed back by the warm (70 - 80F) waters of the Panama Current, and when the temperatures get just right, the Mahi catch is on. Note the underside of the Panama Current pushing from west to east:

The chart below shows the surface ocean temperatures of these waters about a year ago, December 18th, 2010, midway through the poorest mahi season on record.

The undercurrent of the Panama Current, which flows from west to east, failed to contain the northward flow of the Humboldt Current, resulting in water temperatures friendly to sword and tuna, but far too cold for mahi, which stayed 1,000 miles offshore in temperatures more to their liking. The schools were too distant to harvest, meaning the 2011/2012 season would be a good one, should water temperatures cooperate.

And a good season it is! (at least for harvesting).

Note the huge amount of 22 C water, where there was none a year ago. The result has been record catches, day after day … matched only by record ex-vessel prices, day after day, as the market can’t seem to get enough mahi. A year ago the boats got $1.15 a pound, a strong price driven by poor landings. This year they’re getting $2.00 a pound – and they’re catching a lot!
Given we’re at the midway point in the season, the point where a buyer’s thinking goes from “How much does it cost?” to “How much can I get?”