Morphometric variation, length-weight relationship and growth pattern of Pontastacus sp. (Decapoda) from Uzbekistan

The freshwater crayfish of the genus Pontastacus are ecologically and commercially important components of inland water ecosystems, yet the populations inhabiting the water bodies of the Fergana Valley remain poorly characterised. This study examined the morphometric characteristics, length and weight parameters, length-weight relationship, and allometric growth pattern of Pontastacus sp. collected from a lake in eastern Andijan (Khodjaabad, Uzbekistan). A total of 42 crayfish specimens were analysed in April and May of 2025 and 2026, comprising 8 males and 34 females. Total body length of the examined specimens ranged from 44.7 to 95.0 mm and body weight from 2.0 to 11.0 g, with mean values of 70.51 ± 12.39 mm and 5.83 ± 2.37 g, respectively. The highest individual variability was recorded for body weight and for the lengths of the left and right chelae. Although certain morphometric differences between the sexes were observed, they were not statistically significant; because of the strongly unbalanced sex ratio and the limited number of males (n = 8), this result should be interpreted with caution. The length-weight relationship was estimated by linear regression of logtransformed data. In females the relationship was described by the equation W = 0.0643L2.284, and in males by W = 0.0228L2.797. Negative allometric growth was statistically confirmed for the pooled sample (b = 2.378; t = −5.43) and for females (b = 2.284; t = −5.89), whereas in males the growth type did not differ significantly from isometry, most probably because of the small sample size (n = 8). Total body length showed strong positive correlations with body weight and with the other principal morphometric characters. Fulton's condition factor averaged 1.62 ± 0.31 and did not differ between the sexes. These results provide the first morphometric and growth data for this lake population of Pontastacus sp. and may serve as a baseline for further taxonomic, ecological, and monitoring studies of astacofauna in the eastern Fergana Valley.

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