sentences:  The program introduced individual fishing quotas based on each crab fishing boat's previous catches and a requirement that a percentage of the catch be offered for sale in the regions where it was caught.This program was popular with environmental and conservation groups, although some small-scale crab fisherman complained that it placed them at a disadvantage as they could never catch more than their allotted share even if there were more crab available.In addition to overfishing, researchers from the School of Fisheries and Ocean Sciences have hypothesized that prevailing winds may affect crab population numbers from one year to the next.