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specific location is often controlled through the specification of a fishing season. Seasonal closures are temporary in nature and are often used in conjunction with area and gear restrictions. Seasonal restrictions have been used extensively throughout the United States and internationally (Rettig, 1991). A single season may be used, or multiple season openings may be set to spread out landings over time. Seasons can vary in length from months to several minutes as in the case of the fishery for herring roe in the North Pacific region (Hourston, 1980). The typical result of time limits is that the length of the season declines over time as fishing effort increases, so without other management measures, time closures lead to a less efficient and more costly race for fish. The use of seasons or time-area closures generally is not effective in meeting either efficiency or conservation goals (OECD, 1997), although time limits can help processors regulate the flow of product more efficiently, as was the case in the surf clam/ocean quahog (SCOQ) fishery management regime prior to IFQs (Appendix G).
Time limit measures may also specifically limit the number of days at sea. In the SCOQ fisheries prior to IFQs (in 1990), each vessel was allocated a number of hours per week or quarter that it was allowed to fish. In the New England and Mid-Atlantic groundfish and scallop fisheries, time limits are now being imposed through limits on days at sea per vessel (NEFMC, 1996).
Time limits are an attempt to control the effect of excess fishing capacity indirectly. They are only indirect controls because, like other input control measures that limit one dimension of fishing effort, they create incentives to develop other dimensions of effort, such as the fishing power of gear and vessels. Time and season controls can be useful, however, to protect spawning stocks, encourage harvesting at times of peak value, and reduce the effects of localized depletion on forage opportunities for marine mammals and seabirds. However, time limits do nothing to prevent overcapitalization; rather, they encourage it.
Output controls are management techniques that directly limit catch and hence a significant component of fishing mortality (which also includes mortality from bycatch, ghost fishing, and habitat degradation due to fishing). Output controls can be used to set catch limits for an entire fleet or fishery, such as a total allowable catch. They can also be used to set catch limits for specific vessels (trip limits, individual vessel quotas), owners, or operators (individual fishing quotas), so that the sum of the catch limits for individuals or vessels equals the TAC for the entire fishery. Output controls are commonly used in recreational fisheries, taking the form of bag and possession limits that constrain an individual's daily or annual catch.
Output controls rely on the ability to monitor total catch. This can be achieved by either (1) measuring total landed catch with reliable landings records, port-sampling data, and some estimates of discarded or unreported catch; or