In a study published in the current issue of the journal Science, a team of researchers warn that if current fishing trends continue, the world’s commercial fish and seafood stocks will collapse by 2048. This will cause widespread hunger, economic hardships and more polluted oceans. Imposing strong limits on how much fish can be caught and increased fish farming can help remedy the problem.

The percentage of ocean species populations that have collapsed increased dramatically in the 1900s as technical advances made it easier to catch fish and other seafood. In 2003, 29 percent of the world’s currently fished species were considered collapsed.

These species can no longer be caught to feed people and they also leave a hole in the ecosystem. This loss of biodiversity can trigger a cycle where fewer animals are available to filter pollutants from ocean water, leading to algal blooms and fish kills.

University of Maine marine sciences professor Robert Steneck found such a situation in the Gulf of Maine. For thousands of years cod, a top predator, dominated the gulf, keeping other species in check, allowing kelp forests to flourish. In the 1960s, improved fishing techniques allowed fishermen to catch most of the cod, triggering a boom in sea urchins. The urchins cleared entire areas of the gulf of kelp, destroying habitat for young fish such as cod. Once a market for urchins developed, they were harvested in huge numbers and crustacean such as crab and lobster took over. Today, lobsters account for 70 percent of Maine’s seafood harvest, a situation Prof. Steneck warns is not sustainable.

The solution for Maine, and the rest of the world, is strict limits on what can be caught. The Senate has passed a strengthened version of the Magnuson-Stevens Act, the country’s fishery management law. The bill sets clear catch limits for all fisheries and would deduct catches beyond the limits from the next year’s limit. The bill allows for the creation of quota systems to divide up the allowable catch among fishermen.

Because this is a global problem, the Senate bill authorizes the administration to close U.S. ports to countries that allow unregulated and unreported fishing in international waters. The United States did this in the 1990s to control driftnet fishing.

Farming fish, particularly on land, is another promising avenue. However, such operations must focus on fish, such as carp and catfish, that are not carnivorous. Maintaining farms of carnivores like salmon often mean that more fish have to be killed for feed than are produced. Problems with fish waste, disease and parasites must also be addressed for aquaculture to become a viable replacement for ocean fishing as a means of feeding millions of people.

This study, along with ones that preceded it, warn that current fishing practices are not sustainable. Now is the time to restrict catches and improve aquaculture before there are no fish in the sea.