An invasion of fish species into the eastern Mediterranean Sea has brought about dramatic changes in the fishing industry and threatens local species, new Israeli research indicates.
The scope of the fish invasion is the broadest in the world, according to the researchers’ study of fish caught off the Israeli coast two decades ago in comparison to the types caught today.
The study, published last month in the American journal Diversity and Distribution, the study was conducted by Dor Edelist of the University of Haifa, together with Dr. Gil Rilov of the Israel Oceanographic and Limnological Research Center and Dr. Daniel Golani of the Hebrew University of Jerusalem. Dr. James Carlton, an American scientist specializing in invasive species, was also involved in the Haifa University research.
The study was designed to assess changes in the Mediterranean’s fish population due to the ongoing introduction of foreign species from the Indian Ocean and the Red Sea reaching the sea via the Suez Canal. Researchers made several trips in trawlers and examined the catches in 2008-11 and compared their findings data available on catches in 1990-1994.
The findings show that within two decades there had been a dramatic change in the makeup of the catches, particularly at depths between 15-100 meters. If two decades ago the invasive species comprised 29 percent of the catch, now they make up more than half. If 20 years ago these species made up only a quarter of the biomass (the living creatures in a given area), they have now reached 55%.
The researchers note that 55 Indo-Pacific species that arrived via the Suez Canal have established themselves in the Mediterranean, the highest invasion rate of any marine ecosystem. Half of the foreigners were introduced during the past decade and of these, six have multiplied so rapidly that they are among the most common species now found in the eastern Mediterranean.
This extensive invasion, the researchers point out, is not only evident near the coasts and bays of the Eastern Mediterranean, but also in the open sea. The scientists noted a clear invasive trend of other species, not just fish, in the Mediterranean.
From a commercial standpoint, this extensive invasion somewhat compensates for the ongoing depletion of the local fish population due to overfishing. At the same time, the invaders are a factor in the depletion of local species with which they compete for food and breeding sites, often forcing the indigenous species out of their natural habitat.
Haaretz Daily Newspaper Ltd.