During the expedition, the specialists conducted astaccological studies, including collecting data on the crayfish's habitat, biology, spatial distribution, sex and size structure of the population, and disease prevalence.
Observation results showed that the registered catches were dominated by individuals of the recruitment group (7–9 cm) and crayfish of the first commercial group (9–12 cm), of which 44.56% were females. Scientists noted that the main crayfish stocks were concentrated in the Kulikovo-Ordynskaya and Akhtarsko-Grivena groups of estuaries. Large and select crayfish longer than 12 cm were not recorded in the survey catches.
In order to preserve crayfish populations, a ban on commercial and recreational fishing was introduced in the Azov estuaries of Krasnodar Krai in 2016. However, despite these measures, the crayfish's range and productivity continued to decline.
The main natural factors determining crayfish abundance and biomass in the Azov estuaries include unstable hydrological conditions and increased water salinity above optimal levels for crayfish habitation, a series of low-water years due to low Kuban River runoff and the resulting fish kills, increased overgrowth of soft and hard vegetation, and swamping of the estuaries.
As a result, the Chelyabinsk group of estuaries has completely lost its crayfish harvesting potential over the past 15 years. Due to severe overgrowth, low water levels, and regular fish kills, crayfish remain only in one estuary – Sladky.
Furthermore, due to the decrease in freshwater runoff and the increased influx of saltwater from the Sea of Azov, crayfish have disappeared from the Kurchansky Estuary and the Kulikovo-Kurchanskaya group of estuaries.
Restoring the crayfish harvesting potential of the Azov estuaries, given the current increasing salinity of the Sea of Azov, is only possible with increased freshwater Kuban water supplied through the existing system of water supply channels and enhanced monitoring of crayfish populations.
VNIRO Press Service