The findings of four echo-integration surveys are available, three carried out by the same scientific team (Table 22). These data are unfortunately difficult to use since the biomass is insufficiently or not at all separated by species and secondly there is no observation for depths less than 15 or 20 metres. Despite these limitations, it appears that the total biomass is relatively constant whereas it is likely that the relative size of the different stocks has varied considerably, judging from the data available elsewhere (Table 22).
