To support scientific evaluation of the effects of exploitation, STACRES considered the following: landed weights by year, area and species for at least five principal species; by size; annual fishing effort; and estimates of discards, for the development of means for maintaining maximum sustained yield. Thus, the concept of MSY (maximum sustainable yield) was expressed early on by ICNAF as a management objective. This concept was broadened in 1971 to one of achieving optimal utilization.