Weather Wise

A FEW weeks ago, reader Eric Sutherland wrote in complaining that his December scuba-diving holiday in Mexico was ruined thanks to the all-pervasive effects of El Nino.

The warm waters brought to the east Pacific by this anomalous current have caused a depletion in the plankton stocks, leading to a shortage of plankton-eating fish and fish-eating sharks. The tropical waters off the tip of Baja California, the southern reaches of the Sea of Cortes and the western coasts of Central America are normally teeming with exotic fish. This winter, thanks to El Nino, they have been empty - bad news for fishermen and divers.

I managed to have a closer look myself earlier this month. We stayed at the little port of Bahia de Los Angeles, about half-way down the east coast of Baja California, and found it full of happy fishermen; fish were literally leaping out of the water. More than the usual number of whales had been spotted, including the perilously-close-to-extinction blue whale. We were told that, 120 miles to the north, at the resort of San Felipe, the water was thick with hammerhead sharks, who would affectionately nuzzle swimmers.

The reason is simple. The Sea of Cortes acts as a gigantic trap. The warm waters to the south have forced the fish to move north, taking the sharks with them. While the tropical waters to the south are lifeless, the sub-tropical waters north of the 28th parallel have become home to millions of marine refugees.

While El Nino may have damaged the livelihoods of thousands of fishermen to the south, it has proved to be a boon to those further north. This shows that climatic changes, on any scale, temporary or permanent, rarely have a purely positive or negative effect.