engleski

YEAR CYCLE OF ASTACUS LEPTODACTYLUS IN TWO CROATIAN RIVERS

Astacus leptodactylus is one of four native freshwater crayfish inhabiting Croatian inland waters. Comparing data on its distribution from historical sources and recent research, it seems that narrow-clawed crayfish is spreading from the east to the west and south of Croatia. As little is known about its life cycle, therefore the aim of our research was to gather data on narrow-clawed activity throughout a year. The research was conducted in Dobra and Mrežnica rivers (continental Croatia). Crayfish sampling was carried out with baited LiNi traps twice a month, and different physiological crayfish functions and morphometrical characteristics were recorded, as well as physico-chemical parameters of the water. Altogether 311 crayfish were trapped (180 males, 131 females). Sex ratio fluctuated throughout the year, depending on their physiological cycle. The heaviest male was 113 g, and female 125 g, while the longest male was 14.78 cm, and female 16.71 cm. Animals were active all the year around, with the peak of activity in April and June. Preparation for mating started at the end of August and in September (developed glair glands and enlarged gonopods) and juveniles hatched in mid-May. Freshly moulted animals were found from mid-April until September. Main injuries were claw and limb loss, and there were no signs of diseases or epibionts within the studied populations. Correlation of crayfish activity and different physico-chemical parameters of water are discussed in details.

Astacus leptodactylus; year cycle; Croatia

nije evidentirano