Biological characteristics of the Siberian sturgeon catch in the lower reaches of the Lena River near Tit- Ary Island in June 2025

Abstract

The aim: the assessment of the current biological state, qualitative and quantitative composition of the commercial catch and catch per effort of Siberian sturgeon in the lower reaches of the Lena River.

Material: data of the biological analysis of the catch of Siberian sturgeon during the specialized fishery of Nelma and Sturgeon using fixed and drift nets in the second and third ten-day periods of June 2025.

Results: The water level in the Lena River was above the long-term average. The catch per effort was: with set nets –  on average 0.4 specimen/day, with drift nets –  1 specimen/drifting. The size range of Sturgeon varied in total (zoological) length ab from 64.5 cm to 210.5 cm, –  on average 92.2 cm; in length ac (fork length) –  from 56.0 to 160.0 cm, –  on average 82.4 cm. The weight of individuals varied from 1.0 to 31.6 kg. 98 % of the catch corresponded to the commercial measure of 62 cm (fork length) established for this fishery basin. Females and males were equally distributed in the catch. Females are generally larger than males. Females at the III-IV and IV stages of gonad maturity constituted 2/3 of the catch. The size of sexually mature individuals indicates their repeated participation in spawning. This indicates a healthy sturgeon population in the Lena River. The Clarke body condition index (BCI) of Sturgeon averaged 0.46, ranging from 0.36 to 0.69.

Practical value: the research results are applicable to assessing the status of the Siberian sturgeon population in the Lena River, as well as adjusting the total allowable catch of this species.