Density of Undaria pinnatifida in the Mar Piccolo of Taranto

Data report density values (number/0,25 mq) of Undaria pinnatifida thalli in two different study periods: December 2000-November 2002 and December 2006-November 2007. The number of thalli for eight size class in cm (1-3; 4-10; 11-20; 21-30; 31-40; 41-60; 61-80; >80), monthly counted in the field in 30 random squares 50X50 cm, are reported.