Results of comprehensive work to assess the effectiveness of natural fish reproduction in the Astrakhan region

 

The research was conducted to monitor and assess the effectiveness of natural reproduction of anadromous, semi-anadromous, and riverine fish species in inland waters and the coastal zone of the Volga-Caspian fishery subarea. The study subjects were larvae and juveniles of sturgeon, anadromous herring, semi-anadromous fish (roach, bream, pike-perch), and inland fish species such as carp, crucian carp, rudd, white bream, blue bream, pike, and other species.

 

During the low-water flood in 2025, the indicators did not meet fisheries requirements. The first month of summer was practically excluded from the flood period. Of the 73.1 km³ of Volga River discharge in the second quarter, bioproduction flow accounted for 41 km³. Flooding of spawning areas for semi-anadromous and non-anadromous fish began 25 days later than the onset of spawning temperatures of 8.0°C for certain fish species, which had occurred abnormally early – in mid-April of this year. Under these conditions, larval feeding in temporarily flooded areas lasted 25 days, a week less than in the previous, also low-water year of 2024.

 

Water temperatures in the Volga River for certain sturgeon species reached spawning levels by the middle of the second ten-day period of April. Spawners reproduced primarily in channel spawning grounds, where spawning conditions are characterized as less favorable than in spring-flooded (more coastal) rocky ridges. According to estimates, nearly 1.7 times more sturgeon larvae migrated downstream in the spring and summer of 2025 than in 2024 (traditionally, sterlet larvae predominated), but their quality was lower than the previous year.

 

Water temperatures in the Volga River (16.0°C) near the Astrakhan waterway reached spawning levels for anadromous black-backed herring spawning during the first five days of June. Downstream migration of their larvae was observed from the beginning of the first ten days of June to the end of the first ten days of August. The number of downstream-running black-backed herring larvae decreased this year, being 1.3 times lower than in 2024.

 

The most favorable conditions for pike spawners developed at the end of the first five days of April, when the temperature in the Volga River exceeded 4.0°C. Early spawning of crucian carp, Caspian roach, roach, bream, and carp was observed in the eriks of the western and eastern Volga River Delta. A few larvae of certain species were discovered in the third ten-day period of April. The ban on Caspian roach fishing this year has had a positive impact on the duration of spawning migrations, allowing Caspian roach and pike-perch spawners to migrate to more distant water bodies in the lower zone of the Volga-Akhtuba floodplain, including areas of highly productive spawning grounds located there (eight spawning areas with a maximum flooded area of ​​60,000 hectares).

 

A sharp increase in water releases from the Volgograd Hydroelectric Power Plant in the first ten-day period of May and a simultaneous rise in the river water level. The Volga River's rise (2.4 meters in almost a decade) also disrupted the temperature regime during the incubation period of the laid eggs. As a result, clutches with partially dead eggs (usually infected with saprolegnia) were observed on the substrate. This, in turn, caused a slight decrease in the spawning efficiency of roach, bream, and also the most abundant crucian carp. The early decline in the flood level in 2025 prevented the catfish spawners from fully spawning, while also providing satisfactory feeding conditions for their young.

 

The abundance of the majority of larvae, at the fry stage by the end of the flood, was estimated to be almost 2.2 times lower than the level of the previous low-water year of 2024.

 

The results of this year's comprehensive studies were used to assess juvenile yields, the abundance of species generations, and stock sizes, as well as to calculate the TAC and recommended catch of individual aquatic biological resources for the Volga-Caspian fisheries subregion.

 

 

VNIRO Press Service