PRELIMINARY OBSERVATIONS OF AN AMERICAN CRAYFISH PACIFASTACUS LENIUSCULUS (DANA) POPULATION AT A NEW SITE IN THE MAZURIAN LAKE DISTRICT
Tadeusz Krzywosz, Wanda Krzywosz
The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
ABSTRACT. A population of Pacifastacus leniusculus was encountered in a river flowing from a Mazurian lake. It probably originated from individuals that had escaped from a farm where they were reared in 1979-1981. During a single night sampling (June 17-18), 104 crayfish individuals were caught. The sex ratio was 1:1, the males were molting, and the females were bearing offspring. The maximum male body length was 12.7 cm, and that of the females was 12.2 cm. Males over 8 cm in length participated in breeding. The lake and the river have been inhabited for years by Orconectes limosus. However, the presence of that expansive species did not disturb the fairly numerous population of Pacifastacus leniusculus in that section of the river.
Key words: PACIFASTACUS LENIUSCULUS, ORCONECTES LIMOSUS, RIVER, INTRODUCTION, COMPETITION