Fish introductions in the former Soviet Union: The Sevan trout (Salmo ischchan) - 80 years later.

Area of Science:

• Conservation Genetics
• Population Genetics
• Ichthyology

Background:

• The Soviet Union extensively introduced fish species across Eurasia, with limited commercial success.
• Sevan trout (Salmo ischchan), endemic to Lake Sevan, Armenia, was introduced to Central Asia, with the Kirghiz population persisting.
• Previous studies lacked extensive molecular data on Sevan trout populations, hindering conservation assessments.

Purpose of the Study:

• To conduct the first extensive molecular study on Sevan trout (Salmo ischchan).
• To compare genetic diversity and differentiation between native Armenian and introduced Kirghiz populations.
• To assess the impact of past introductions, hatchery practices, and environmental factors on Sevan trout genetic variability.

Main Methods:

• Analysis of 11 nuclear microsatellite markers.
• Sequencing of a 905 bp fragment of the mitochondrial control region.
• Sampling from native Lake Sevan, Armenian hatcheries, and the introduced Lake Issyk Kul population in Kyrgyzstan.

Main Results:

• The introduced Kirghiz population is genetically differentiated from native and hatchery populations.
• Hatcheries appear to maintain genetic diversity through translocations, while wild populations show signs of past bottlenecks.
• The introduced Kirghiz population exhibits unique morphological and biological traits and a larger effective population size than the native stock.

Conclusions:

• Introduced Sevan trout in Kyrgyzstan have diverged significantly, potentially adapting to new environments.
• Past environmental pressures like water manipulation and poaching likely impacted native Sevan trout genetic diversity.
• Urgent conservation measures are recommended for the native Lake Sevan population due to its lower effective population size.