UK: Exploring fish invasion

Bournemouth University Professor Rudy Gozlan (pictured) is leading an Anglo-Chinese expedition through remote parts of China to discover the origins of a global fish invasion.

Together with colleagues from the university and the Chinese Academy of Science, Gozlan will travel more than 10,000 kilometres along two major rivers - the Yellow and the Yangtze - to collect samples of a species of Topmouth gudgeon.

Gozlan, of the university's Centre for Conservation Ecology and Environmental Change, is producing a blog of his journey.

The expedition represents a scientific, cultural and historical journey as Gozlan traces the historic movement of the gudgeon from its native East China to become one of the world's most prolific invasive species with populations extending as far as Europe and North Africa.

Gozlan has identified that populations of the Topmouth gudgeon outside China are healthy carriers of a deadly non-species specific parasite Sphaerothecum destruens. These parasite-carrying gudgeons pose a threat to fish diversity, particularly in Europe where invaluable salmon stocks important to Britain's aquaculture industry are at risk.

"This is the story of an innocent movement of fish from the East coast to the West part of China which has rippled all the way to Britain some 50 years later," said Gozlan.

"The Topmouth gudgeon is small in size with a maximum length of about nine centimetres, highly fecund with batch- spawning and nest- guarding behaviour and highly tolerant to environmental changes giving it all of the attributes of a successful invader."

The Topmouth gudgeon's first introduction outside China was in reservoirs and ponds around the Black Sea as part of a fish- farming agreement between China and the former Eastern bloc. Following long distances and hitchhiking cross country with movements of carp, it rapidly escaped and colonised local waters, dominating communities in ponds and lakes.

"The gudgeon's stealth invasion of the world started in the 1950s with the end of the Chinese civil war (from around 1840 to 1949) which had restricted human population mobility and trade," said Gozlan.

"At that time, there was an increasing need for developing new sources of animal protein and black carp, grass carp, silver carp and big head carp were rapidly introduced from East China especially from the middle and lower reaches of the Yangtze River basin to many other places including Yunnan, Qinghai, Gansu and Xinjiang.

"This species had been cultured traditionally in East China for a long time with specific culturing techniques," he continued. "These carp introductions for aquaculture, however, have been the beachhead of Topmouth gudgeon's great escape."

During the expedition, Gozlan is gathering material including live samples of Topmouth gudgeon from 33 locations covering nine major catchments. The samples will be compared to material collected from populations established from the first introduction in each country within the non-native range.

Populations will be compared for their life history traits and parasitic communities as well as their population genetic structure within the native range but also across the introduced range.