Fauna Journal Entry

Jellyfish Invade Caspian Sea (October 27, 2000)

An invading jellyfish species is devouring microscopic food sources in the Caspian Sea. The fist-sized comb jellyfish (Mnemiopsis leidyi) is native to estuaries on the East Coast of North America. The jellyfish likely made their way to Europe in ship ballasts.

They were first discovered in Europe's Black Sea in the late 1980s. They virtually emptied the Black Sea of tiny marine organisms known as zooplankton, an important part of the sea's food chain. The jellyfish also consume fish eggs.

Now, scientists have found that the jellyfish are causing harm in the Caspian Sea to the east of the Black Sea. The invasion is expected to cause great damage to the Caspian fishing industry.

The first victims will likely be kilka, a group of several sardine-like species that feed on zooplankton. The disaster will then affect the sea's larger fish and 100,000 to 300,000 remaining Caspian seals, which feed on kilka. The seal population has already been hurt by pollution and disease.

Some marine scientists have suggested introducing milkfish from North America to the Caspian Sea. Milkfish are a natural predator of the invading jellyfish. They can eat up to ten times their body mass of the jellyfish each day. Another possibility is to introduce another species of comb jellyfish from the Black Sea that preys on the invading species.