Growth, Diet and Fatty Acid Composition of Gibel Carp Carassius Gibelio in Lake Shira, a Brackish Water Body in Southern Siberia

Abstract

For the first time the presence of gibel carp Carassius gibelio has been detected in the brackishmeromictic Lake Shira (Southern Siberia, Republic of Khakassia). Lake Shira has been continuouslystudied since the late 19th century, and it has been considered so far that there is no ichthyofauna inthe lake. This work investigates the growth and population characteristics, as well as food spectraand fatty acid composition of C. gibelio specimen at different ages that were fished out in the summersof 2007 and 2008. The water salinity at the fishing point was 15 g l-1. The food spectrum of one- andtwo-year old C. gibelio was dominated by diatomic, green and blue-green algae, while four- to sixyearold species had an increased share of copepods, beetles and chironomids in their food spectrum,and beginning from the age of six years the amphipods Gammarus lacustris consisted significant partof gibel carp diet. Thus, it was shown that C. gibelio is a carnivore with regard to the population ofamphipods Gammarus lacustris, which have been regarded so far as the upper link in the trophiccascade of Lake Shira. One of the possible reasons for appearance of fish is the decreased water salinitycaused by rising of the lake level. In the recent years, the level of Lake Shira exceeded all the valuesthat had been registered since the late 19th century, and the lake’s salinity decreased correspondingly to its smallest value for the whole period of observation.