BIOLOGICAL ASPECTS OF PLESIONIKA-ANTIGAI (ZARIQUIEY ALVAREZ, 1955) (CRUSTACEA, DECAPODA, PANDALIDAE) IN CENTRAL-WESTERN MEDITERRANEAN

From a series of samples collected in 1995 by fishing trawlers it was possible to establish the distribution areas of Plesionika antigai (Za riquiey Alvarez) in the seas around Sardinia. P. antigai was generally found from 200 to 600 m depth and was most abundant between 400 and 4 50 m. It was found in different proportions together with Plesionika h eterocarpus (A. Costa) in 16 of the 120 castings, between 380 and 500 m of depth. The specimens examined were in the following CL ranges: ma les 2.4-16.9 mm, females 2.5-17.5 mm. On the whole the sex ratio (m/f) was 0.6 in favour of the females; this value, however, seems to decre ase according to increasing depth, with a reduction in the number of m ales with respect to females. Ovigerous females were present all year round with particularly high percentage frequency values between June and November. Calculated size at first maturity in these months was 10 .0 and 9.7 mm CL, respectively. The stage immediately before hatching is most common in June. Finally, the value obtained from the yearly su mmation of the relative monthly frequencies of stage three ovigerous f emales, which was 200, agreed with the values reported for other decap od crustaceans that spawn more than once a year.