Diversity of fish, population structure and dynamics in Paravani and Sagamo Lake
Sagamo and Paravani lakes are important ponds, by their richness with fishes and for trade fisheries. The lakes are located in Javakheti upland at altitude 2000 – 2100 m and the distance between them is 10 km. They connected with the river Paravani, it is a great possibility to migrate actively for different species. Paravani lake used to be considered as fisheries important water body, however during the Last 40 years, study of Javakheti lakes was not conducted and a condition of the fish fauna is unknown. This time coincide also to the period of gibel carp (Carassius gibelio) invasion, which became one of dominant fish for both lakes and this fact may cause a rapid change of lakes ichtyofauna. To foresee that during the last 20 years intensity of uncontrolled catchments has risen, it’s very important to study and detect a tendencies of the changes in fish population. Study of fish population is important in terms to estimate the tendency of fish population changes and to asses an ecosystem condition. Furthermore, study of fish population structure gives us possibility to define the fish population state after applying management events. Good habitat is vital for fishes, so it is important to pay attention on lake management.
There is no updated data about Paravani and Sagamo lake. Hence the aim of this project is: a) to determine Sagamo and Paravani lakes fish species diversity, their quantitative and sex ratio; b) study of meristic features of fishes based on morphologic study; c) study of age structure; d) assessment of population structure and abundance; e) length-weight relationships.
Samples were collected from Paravani and Sagamo Lake during 2015-2016 year (3 seasons). Totally 8 fish species with 1003 individuals were collected. Fish was investigated in a field and in a laboratory.
The results has shown that fish species diversity and population structure has changed compering to historical data. For example one of the dominant species in the Sagamo lake is an invasive gibel carp. Several species (Cyprinus carpio, Rutilus rutilus) which were inhabiting this lakes are not appearing nowadays. Locals inform us that thay have not seen these species (in addition with Salmo trutta fario) for a long time and it is possible that they become extinct locally. In spite of Paravani lake is several times bigger than Sagamo lake, its ichtiopauna is poor. It may caused by uncontrolled fishing. It should be mentioned that around Paravani lake there are 6 villages located, and unsystematic fishing for its residents is a main activity. They often leave gill nets in the lake, which are staying there during the years and cusses additional mortality of fishes. Comparing to Paravani, ichtiophauna of Sagamo lake is not under the human impact and therefore fish are more diverse and their population is more stable.