In June 2002, a pilot tagging experiment has been conducted by Ifremer on the “Grande Vasière', a nursery area situated in the northern part of the Bay of Biscay. 1307 hakes in the size range 13-58 cm (with a mode at 28 cm) have been tagged and released (de Pontual et al., 2003). To date, 40 have been recovered with a time at liberty from 1 to 440 days. Preliminary results from this experiment indicate that growth could be under-estimated (see poster CM 2004/K:66 ). In this poster, we look at the potential effects changes in growth rates may have on the northern stock assessments of hake and management conducted by ICES. This is carried out by a simulation approach.