The new Observer Program restructures and replaces what was originally considered an "interim program," which lasted for 23 years. Broadly speaking, under the interim program, vessels and plants paid for observers by the day at coverage rates specified in law based on days in a calendar quarter at-sea (not fishery as is often assumed) and on tons processed for shoreside processors. Under the interim program, catcher vessels between 60 and 125 ft in overall length were allowed to self-select which trips were to be observed. Because vessels less than 60 ft or those targeting Pacific halibut were not observed, the former static regulatory structure of observer coverage created not only an incentive for owners to change the length of their vessels (indeed a disproportionately high number of 124 ft and 58 ft vessels exist in the fleet), but also created a mechanism for owners, because of self-selected trips, to skew observer coverage towards trips with lower bycatch rates (e.g. pollock) and away from those with higher bycatch rates (e.g. most flatfish fisheries).