Preserving the natural structure of fish populations within the reserve area can, ultimately, enhance the resiliency of these populations to outside pressures. Marine reserves increase the individual size and abundance of fish both inside and outside their borders. There is evidence from around the world that marine reserves support fish populations of increased abundance, density, size, and age classes within their borders. These benefits allow protected populations to increase their reproductive output and potentially replenish fisheries outside their borders through dispersal of eggs and larvae. Marine reserves may also replenish nearby fisheries through direct migration of adult fish.
Marine reserves provide insurance against scientific uncertainty.
One of the greatest challenges in fishery management is the uncertainty associated with setting safe and appropriate catch levels for individual fish stocks and trying to predict variations in natural conditions. Marine reserves can protect a portion of fish populations from potentially irreversible damage resulting from erroneous fishery management decisions. Marine reserves provide scientific research opportunities. Marine reserves can improve the scientific basis for fishery management decisionmaking by offering scientists ecological benchmarks against which fishing impacts can be measured, as well as baseline data on the age, growth, life history parameters and ecological interactions of marine communities. Marine reserves are difficult to properly design and site.