Colatura is the traditional Italian fish sauce made from anchovies that is an important part of the Mediterranean diet. Historically called garum, it literally saved the fishing industry during the era of the Roman Empire. After thousands of years, the diminishing supply of anchovies is causing another shift in the industry. One reason is overfishing among the 22 nations that surround the Mediterranean, and another is the tuna, now regulated, that eat them.
But there are also profound changes occurring beyond overfishing. When Egypt dammed the Nile at Aswan in the 1950s, the rich nutrients that once fertilized phytoplankton and prompted them to bloom stopped reaching the sea. On top of that, the yearly cycles of wind and weather have changed, redirecting whole populations of species out of their usual migration routes. In some cases, this is only a geographical adjustment. But more disturbing is a much larger shift, a decoupling, in fact, of the ancient predator-prey relationship that occurs on a microscopic level at the very bottom of the marine food web. The essential relationship of phytoplankton and the zooplankton that feed upon them is changing. Phytoplankton are triggered to bloom by light. As the days grow longer after the winter solstice they increase their numbers. Zooplankton, the first rung up from phytoplankton on the marine food web, are cued by temperature. With waters growing warmer and warmer each year, zooplankton are hatching too early—before the phytoplankton bloom. As a result, both types of plankton, zoo- and phyto-, crash prematurely before juvenile fish, like anchovies, have a chance to feed on them. It is partly for this reason that every year the Mediterranean gets clearer and more beautiful even as it contains less and less life.