However, quota shares are not rights to particular fish. Consequently, quota holders have no assurance that other quota holders will refrain from practices that prevent the sustainable use of fish stocks. Some argue that precisely because IFQ management provides an opportunity to conduct fisheries more slowly, selective harvesting of higher-value fish (highgrading) may occur. Highgrading is most likely to occur when catch rates are high and there is a significant price advantage to fish of a particular size, gender, or spawning condition. The incentive to highgrade is also increased when the TAC is expressed in the total number of fish rather than their total weight. Some also believe that because monitoring and enforcing harvests is difficult, the incentive to misreport catches, also known as quota busting, is sufficiently high to outweigh the potential risk of being caught. Individuals practicing stewardship may incur the full marginal cost of forgone catches and receive only the average of the increased future benefits. This illustrates the phenomenon of externalities, situations in which the costs or benefits are not fully borne by the individual user. Therefore, IFQ holders may have an incentive to conserve at less than the socially optimal level, especially when there are large numbers of them (and hence a smaller average benefit). This rationale demonstrates that IFQ fisheries require effective monitoring, enforcement, and penalties to achieve their benefits.
The net effect of IFQs on conservation will depend on the relative strength of the stewardship effect balanced with enforcement and the incentives for each individual quota holder to cheat. Sorting and discarding fish to high-grade costs money and will occur only if the expected benefits exceed the cost of sorting and the cost of catching replacement fish (including the opportunity cost of time and the expected cost of penalties and sanctions). The general conclusion of a 1990 workshop on the effects of different fishery management schemes on bycatch, "joint catch," and discards was that IFQ programs are no better or worse than other fishery management schemes in relation to these factors (Dewees and Ueber, 1990). Beyond the theories, few data exist regarding the positive or negative stewardship effects of IFQs, although there are some indications in the Pacific halibut fishery (Gilroy et al., 1996) that IFQs decrease regulatory discards and ghost fishing.
The third rationale for implementing an IFQ program is to improve safety in a fishery, a goal of the new National Standard 10 (Sec. 301[a]). It is argued that because an IFQ program allows greater freedom for the individual to choose when to fish, weather conditions, the condition of the vessel, or other safety factors can be considered and hazardous conditions can be avoided. Although empirical evidence suggests that safety has improved in some IFQ-managed fisheries, it is not clear that safety has improved in all fisheries managed using IFQs.