most common methods used to control fishing effort. Temporal closures are also implemented to protect fishery resources at times when they are particularly vulnerable, such as when fish are aggregated on spawning grounds.
MPAs will also shift patterns of fishing effort, and management plans should be designed to take these expected changes into account. Temporal closures aimed at limiting fishing mortality can be effective if regulators correctly anticipate or control the fishery's reaction to time (and area) closures. A closure in one area will typically result in increased effort elsewhere.
In some cases, rotating areas of closure for specified periods has been used to promote growth of young animals, allowing them to reach more valuable sizes. This approach combines temporal and spatial closures to regulate fishing and could supplement benefits from fully protected reserves. As an example, the State of Washington has instituted rotating closures in its sea urchin fishery to control effort and allow populations to recover to marketable sizes and quantities. Rotating closures may help protect habitat and biological communities in addition to target species by allowing areas altered by fishing gear to recover during respites from fishing. However, if the period of closure is short, the area may have insufficient time to recover, jeopardizing the full recovery of the target stock.
Longer-term closures may be instituted as single-species refuges from fishing. In this approach, the goals focus on rebuilding or restoration, with long-term success dependent on more precautionary management after the stock recovers. One recent long-term closure in California, implemented for chinook salmon (Oncorhynchus tshawytscha) in the Klamath River area, closed the entire (mixed-species) salmon fishery off the coast to allow recovery. In another example, closure of the severely depleted striped bass (Morone saxatilis) fishery along much of the east coast of the United States in the 1980s was effective in promoting recovery of the species and reestablishment of the fishery (Field, 1997; Richards and Rago, 1999). Unfortunately, there are few alternatives to long-term closures of large areas when fish populations have collapsed, and restoration of the abundance and age structure of the depleted population may require many years. One goal of MPAs is to provide insurance against stock collapse (Chapter 5), reducing the need for such drastic measures.
Single-species closed areas lack many of the key conservation benefits of permanent reserves, but they provide an important tool to control fishing effort and supplement more comprehensive MPAs. There are some examples of temporal closures to address multispecies or ecosystem concerns rather than single-species fishery management. For instance, closure of large areas in the Bering Sea around Steller's sea lion (Eumetopias jubatus) habitat during the walleye pollock (Theragra chalcogramma) fishing season is an example of the use of temporal area closures with broader conservation objectives.
Although temporal closures have value as a tool for fishery management, this approach does not yield the benefits sought with the establishment of MPAs.