You could compare mismanaging fish stocks to mismanaging your credit. Spending more money than you make as a regular practice is like regularly over-fishing to catch more fish and make more money than the fish stocks can normally produce. Sooner or later your standard of living will start to decline just as the number of fish caught will start to decline as you continue overfishing. In extreme examples one can go bankrupt and fish stocks can collapse. For many of the world's fisheries we are borrowing against the future, and while there may be social or economic pressures to continue to over fish, we will just be postponing the pain if we don't limit our killing of the fish to the amount of fish their stocks can sustain.
Marine reserves are one of the answers to get back on track.
To be sure we use this management tool wisely, we need to be clear about what we are trying to accomplish. In thinking this through, we should recall that there are two basic reasons for establishing marine reserves. First, as discussed above, a prime reason is to use reserves as a fishery management tool to restore and maintain fish stocks. As such, marine reserves may be established on a temporary, seasonal or spatial basis, or they may essentially be permanent. Fishery managers in fact have used closures as part of their tool set for a long time, so marine reserves are not a new concept.