In some areas Blackchin tilapia can make up to 90% of the fish biomass.

Bolinopsis, Mnemiopsis, and the tentacle-less Beroe can also be found fairly frequently.

Mnemiopsis is able to eat over ten times its own body weight in food, and to double in size, each day.

In the Black Sea, the filter-feeding North American jellyfish Mnemiopsis leidyi has on occasion reached densities of 1kg of biomass per m2.

One study showed that Mnemiopsis removed over 30 percent of the copepod (small marine crustaceans) population available to it each day.

In the Black Sea, the filter-feeding North American jellyfish Mnemiopsis leidyi has on occasion reached densities of 1kg of biomass per m2.

As an example, she points to a species of jellyfish called Mnemiopsis leidyi that was accidentally introduced into the Black Sea in the early 1980s.

The invasiveness of the comb jelly M. Leidyi in the North Sea in the 80s has led to a major change in the marine ecosystem and economic losses.

The MEMO project (Mnemiopsis leidyi:Ecology, Modelling and Observation), is examining their biology and physiology in an attempt to monitor the impact the jellyfish are having on commercial fish and shellfish stocks.

By 2002 the total weight of Mnemiopsis in the Black Sea had grown so prodigiously that it was estimated to be ten times greater than the weight of all fish caught throughout the entire world in a year.

In the 1990s, another combjelly species Beroe ovata from north-western Atlantic and preying almost exclusively on Mnemiopsis leidyi, was also accidentally introduced in the Black Sea ecosystem.

Introduced in the Black Sea, most likely via ballast waters of cargo ships, Mnemiopsis leidyi feeds on fish larvae as well as organisms that would otherwise feed the anchovy.

This “stealth predation” is a predator of Mnemiopsis very effective generalist, which captures a wide range of microplantoniche prey (ie approximately 50 m),, of copepods (+/- 1 mm) and fish larvae (up to 3 mm or more).

By 2002 the total weight of Mnemiopsis in the Black Sea had grown so prodigiously that it was estimated to be ten times greater than the weight of all fish caught throughout the entire world in a year.