Биология окуня бассейна верхнего течения реки Лены

Abstract

Lena River is the largest watercourse in Eastern Siberia. The upper reaches of the river, 1600 km long, starts from the source to the mouth of the Vitim River. We collected data on perch biology in different seasons: in the Lena River in the section from the mouth of the Tutura River (right tributary 3,812 km from the mouth) to the mouth of the Ichora River (left tributary 2,973 km from the mouth) in different seasons from 2007 to 2022; in the Kuta 10-km section from 10 to 20 km from the river mouth in August 2011; Kirenga River from the mouth of the Marekta Brook (400 km from the mouth) to the mouth of the Garynya Brook (379 km) in April 2016, June 2013-2014, September 2014 and October 2015, at 217 km, the mouth of the Cherepanikha River (144 km) and Ichikta River (82 km), June 2022; the Piljuda (left tributary 3050 km from the mouth), April 2010, May 2017 and June 2019; Vitim River. In rhe Vitim river main channel (582 km from the river mouth) to a nameless creek (551 km from the river mouth), June, September 2010 and June, August 2012; in four lakes in Okunayka River – Kirenga River basin: Lake Blizhnee, July 2012; Lake Dal'nee, July-August 2012, July and September 2015; Lake Durgan, July and September 2012, August 2012, July, 2017 and September 2015; Lake Podkova, September 2015; Lake Golubtsovskoe (Vitim River along the right bank 5.5 km upstream Labazny Brook (561 km from the mouth)), June and September 2010, August 2012. The perch in the investigated sites is one of the most numerous in the composition of fish fauna, occupying from 8.29 % to 61.43 % in catches. In the sections of the Lena and Kirenga rivers where the least anthropogenic load is observed, in the Dalneye and Durgan lakes a complex age structure is characteristic, consisting of more than 10 age groups, with the predominance of fish of 4-5+ age in catches. The lowest age range is observed in the reservoirs where active fishing is observed; in the Kuta River and the Piljuda River the age range in catches is represented by 4 and 6 age groups, with predominance in catches of fish of 1+ age. The highest rates of linear weight growth among riverine populations are characteristic of fish from the main channel of the Lena River and the Kirenga River, slightly lower from the Vitim River. The lowest rates were recorded for perch from the Kuta and Peluda rivers. Among lacustrinal populations, the greatest growth is characteristic to perch from Dal’nee Lake and nearby Podkova Lake, the smallest being demonstrated by fish from the small floodplain lake Golubtsovskoye. Sex ratio of perch population in the main channel of Upper Lena is characterized by the change in the ratio of males and females with age from 1:0,69 in younger age groups to 1:1,9 in older age groups. In the Vitim River it is 1:1.55. In the Kirenga River it is 1:1.2 with an almost threefold superiority of females at age four. In the Dal’nee Lake, the proportion varies from 1:0.75 to 1:2.5 with age. In lakes Durgan, Blizhnee and Golubtsovskoe an essential prevalence of females over males in all age groups is observed; on the average it is 1:3.6, 1:1.4 and 1:1.7, respectively. Maturity in the Lena’s main channel occurs sporadically in males at the second year of life, in females one year later; in the Kirenga River at the age of three years; in the Vitim River, in males at the third year of life, in females at the fourth. Spawning takes place in the second half of May to early June. The absolute individual fecundity of perch from the Lena River averaged 27,200 eggs, 12,053 in the Peluda River, 32,400 in the Kirenga River, 30,780 eggs in Lake Dal’nee, 23,329 eggs in Lake Durgan, and 27,923 eggs in Lake Podkova. Perch is a predator by nature of feeding, the gudgeon and river minnow are the main food items in the Lena River, river minnow and Amur minnow in the Kirenga River, ruff, river minnow and young of their own species in the Vitim River, benthic organisms in the majority of lake reservoirs.