SPNI workers - Zafrir Rinat - 27122011
SPNI workers at Ein Maklef spring, near Mevasseret Zion on Sunday. Photo by Zafrir Rinat
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Ariel Filber and Assaf Galdor made their way on Monday from the Society for the Protection of Nature in Israel's field school in Ofra to a small spring near Jerusalem, Ein Maklef. They put on rubber fly-fishing overalls and waders and, using fishing nets, they methodically scooped scores of goldfish out of the pool next to the spring.

The fishing expedition was part of an operation to remove invasive fish species that people have tossed into dozens of springs. The SPNI's Alon Rothschild says these fish threaten the springs' native crab, fish and amphibian populations, competing with them for food or eating their eggs.

According to Rothschild, it has become a serious problem in several parts of the country. "There are groups of people whose hobby is restoring springs, including building pools to collect the spring water. Part of the restoration includes putting goldfish into the ponds," Rothschild says.

Some of the fish are introduced by people who want to get rid of them, while others come from people who believe putting goldfish in a pool brings luck. A group calling itself Abarbanel, or the Abarbanelim, specializes in restoring springs, usually without any authorization. Its "trademark" is "liberating" goldfish by introducing them into the pools.

At least 10 invasive fish species - mainly various species of carp, including goldfish - are thought to have been introduced into springs around the country. Another prominent invasive species is the mosquitofish (Gambusia affinis ), first introduced in the 1920s to eat the larvae of malaria-bearing mosquitoes. In a laboratory setting, at least, the mosquitofish has also shown a taste for the tadpoles of certain endangered amphibian species.

Filber and Galdor have removed fish from more than a dozen springs in Samaria and in the Jerusalem vicinity since they began, around a month ago.

"We come to a spring, check the depth of the pool and then wade in with the net," Filber explains. "We're careful to release back into the pool anything that belongs there naturally." They put the invasive individuals into a container containing water and try to find homes for them with fish breeders. Filber says that one of the springs contained more than 100 small fish and 10 large ones.

Hikers coming to the springs are generally surprised at the site of two young men scooping fish out of them, assuming that they are bent on harm. SPNI has published informational literature explaining the ecological implications of releasing non-native fish into natural springs. "We know that a lot of the time, the people putting the fish into the pools are not aware of the implications," Rotshchild stresses.

He says people must be made aware not only of the importance of not introducing invasive species into the springs, but also of the problems associated with building artificial pools in or near natural springs. These, he says, can change the circulation of the water and disturb the development of plant and animal life. Rothschild emphasizes that diverting a water source without permission is a criminal offense.