Ludoga Sig. Family: Salmonidae.
Representatives of this family are widely distributed in the basins of rivers flowing into the Arctic Ocean. Similar to salmon, the sig family, being fish of northern origin, inhabit water bodies with clean, clear water and sandy-stony bottoms. These are generally cold-water bodies with a rich content of dissolved oxygen in the water. Among the sig fish, there are typically migratory and resident forms capable of living in closed lakes.
In terms of feeding habits, they are also diverse: some feed exclusively on benthic organisms (benthophages), others specialize in feeding on planktonic organisms inhabiting the water column, while others have adapted to predation or exhibit the ability to be polyphagous, meaning that at different stages of their lives they can feed on both planktonic organisms and benthos, and even engage in predation.
The history of the formation of fish populations in the water bodies of Kyrgyzstan has been such that neither salmon nor sig have penetrated the rivers and lakes of our region, although some species of fish from northern latitudes have appeared in the water bodies of Northern Kyrgyzstan (such as elcy, pike, and loach).
In the lakes of Kyrgyzstan, sig have been artificially bred. Following the recommendation of Professor F. A. Turdakova, in the 1960s and 70s, ludoga sig, peled, rypushka, and Baikal omul were introduced into Lake Issyk-Kul by workers from the Main Fishery Management of the USSR, while peled, chir, and presumably accidentally a batch of ludoga sig eggs from the Velikoluksky hatchery were introduced into Lake Son-Kul.
Of the listed species of sig fish, only sig and Baikal omul have acclimatized in Issyk-Kul, with the latter becoming quite rare since the early 1980s. Peled and rypushka did not survive in Issyk-Kul due to the lack of spawning conditions and extremely low biomass of plankton, their main food source. In Son-Kul, sig and peled acclimatized well, while chir, being a migratory fish, could not find suitable conditions for reproduction, and the last specimens were caught by fishermen in the early 1980s.
Ludoga Sig
In Lake Issyk-Kul, sig was introduced from Lake Sevan (Armenia) in the form of fertilized eggs. From 1966 to 1982, a total of 90.8 million larvae and 21.9 million juvenile sig were released into the lake. Currently, sig can be found everywhere in Issyk-Kul, but the highest concentrations are formed in the freshened areas of the eastern part of the lake — in the Tyup and Jergalan bays, where the largest rivers of the lake basin — Tyup and Jergalan — flow in.
According to M. N. Alpieva, with the onset of autumn cooling, when the water temperature in the lake drops to 10-11°C, the concentration of sig schools in the shallow zone sharply increases. From about mid-October, they approach the mouths of the Tyup and Jergalan rivers, where they concentrate at depths of 1-10 meters. By mid-November, the concentration of schools of this species sharply increases.
Spawning of Sig
At the beginning of the approach of sig to the shallow zone (until mid-October), males predominately make up the schools, while by mid-November, the sex ratio becomes equal. No one has yet succeeded in observing the spawning of sig in Issyk-Kul and its tributaries, although there are places at the mouths of rivers and in freshened areas of bays and backwaters where sig could potentially spawn.
The absolute individual fecundity of sig in Issyk-Kul, according to M. N. Alpieva, varies from 26.5 to 99.0 thousand eggs depending on the size and age of the females. According to M. N. Alpieva and S. S. Lysenko, sig grow quite quickly in the lakes of Kyrgyzstan, especially in Lake Issyk-Kul.
It should be noted that sig, like other representatives of this genus, exhibit a high degree of morphological and ecological variability, both within their range and beyond it during artificial dispersal. Long-term observations by M. N. Alpieva and S. S. Lysenko have established that in the lakes Issyk-Kul and Son-Kul, ludoga sig has formed two well-distinguishable growth forms — fast-growing and slow-growing. Additionally, in Lake Son-Kul, two varieties of sig have emerged — low-spined and multi-spined, among which there are individuals with both fast and slow growth rates.
In Lake Son-Kul, sig feeds on the amphipod Gammarus, mollusks, chironomid larvae, and loaches, while in Issyk-Kul, the main part of this fish's diet consists of crustaceans (mysids and Gammarus), mollusks, chironomid larvae, and small non-commercial fish (loaches, nase, etc.).
In the deep waters of Lake Issyk-Kul, two more or less well-defined migrations of sig are observed from the deep-water zone (60-150 m) to shallow waters — in April-May and September-October. The spring migration is for feeding, while the autumn migration is for spawning. In April, sig, leaving their wintering grounds, move into shallow waters, spreading out alone or in small groups across the bays and in the pre-mouth areas of rivers, where they feed intensively on mollusks, mysids, and small fish. In the shallow zone, at depths of 5-30 meters, sig remain until the end of June — early July, after which they migrate to deeper parts of the lake.
The autumn approach of mature sig to the shallow waters is driven by the instinct to reproduce. Sig move into the most freshened areas, to the mouths of rivers (Tyup, Jergalan, etc.) or to regions where springs are observed in the shallow zone, for example, in the southwestern part of the lake near Ula-Khol — Ak-Ulyon. Despite the fact that sig began to be introduced into Issyk-Kul in 1966, their numbers in the lake remained insignificant for many years, as their stocks are mainly formed through artificial reproduction.
It should be mentioned that the rampant poaching in Issyk-Kul is also a negative factor in the formation of stocks of commercial fish, especially valuable species like trout and sig. Experimental fishing for sig in Issyk-Kul was only opened in 1980, when 40 quintals were caught. In the following years, catches of sig began to increase.
“Fish of Kyrgyzstan,” I.A. Pivneva
Fish