players in controlling algal growth on the reefs. Following the die-off of the urchin population and damage to the reefs from two hurricanes, algal growth smothered the remaining coral (Hughes, 1994). A similar occurrence in St. Lucia confirmed that overfishing led to algal overgrowth on the reefs. In St. Lucia, shifts from coral to algal domination occurred only in fished areas, while in reserves, higher densities of grazing parrotfish controlled algal growth and prevented coral losses (Hughes, 1994). At a broader scale, coral cover in the Caribbean appears to be increasing only where there are well-managed marine parks and reserves (Ogden, 1997).
The above examples illustrate how reserves can prevent or reverse indirect fishing effects on habitat. Of greater concern in some regions are the direct and indirect effects of mobile fishing gears such as trawls and dredges (Safina, 1998a; Watling and Norse, 1998). This gear can destroy delicate biogenic habitats that may have taken centuries to develop (Dayton et al., 1995; Koslow, 1997). Most of the Oculina coral reefs of southeastern Florida have been reduced to rubble by trawling (Scanlon, 1998; Koenig et al., 2000). To avoid a similar fate, Norway established two reserves to protect deep-water Lophelia coral beds that recently became vulnerable after the introduction of “rock-hopper” trawls for fishing on rough seabeds. Also, there have been proposals to establish reserves on the Scotian Shelf off Nova Scotia to protect stands of deep-ocean soft corals that are vulnerable to damage from trawling gear (Kenchington et al., in press; Willison et al., in press).
Marine reserves clearly offer a reliable means to protect habitat, especially where fishing gear has been shown to destroy fragile, slow-growing, biogenic habitat such as corals. Often, there are no clear alternatives for protecting spawning sites and nursery grounds (Minns et al., 1996), although gear restrictions might be effective in some situations.
Research in marine reserves is now a fast-growing field of endeavor. Although they rarely appeared in the literature previously, the terms “marine reserves” and “marine protected areas” have increased dramatically in frequency in journal articles since 1993 (Conover et al., 2000). Studies evaluating reserve effects can be found in Roberts and Polunin (1991, 1993a); Dugan and Davis (1993); Rowley (1994); Bohnsack (1996); Allison et al. (1998); and Guénette et al. (1998). However, in the United States, there are very few closed areas that can be studied. The recent executive order from President Clinton ( Appendix E), directing the Departments of Commerce and Interior to establish a national system of marine protected areas, could change this significantly.