Aquaculture, the practice of cultivating aquatic animals for food, like agriculture, is not inherently “evil.” The problem arises when these operations become highly industrialized and intricately connected to the global resource flow. The “problem” with industrialized aquaculture is its negative effects to both human and environmental health.

Aquaculture comes in many forms, and marine aquaculture is a small subset. Of them all, shrimp farming results in arguably more negative externalities — both social and environmental — than any other form of aquaculture. Shrimp is cultivated in earthen ponds filled with seawater. The pond water is kept clean to prevent mortality by regular flushing with freshwater. The majority of the shrimp we eat today are farmed in the coastal areas of developing countries in the tropics — for example, Bangladesh, Thailand, Indonesia, Ecuador, Brazil, Madagascar … and the list goes on. In everywhere it occurs, shrimp farming is wreaking havoc.

The externalities are multiple: coastal habitat conversion (mostly mangroves), depletion of wild population of larvae for stocking, salinization of surrounding soils and water; competition for freshwater; transfer of alien species; eutrophication; misuse of treatment chemicals and more. The largest shrimp farm in the world is in Indonesia — it is the size of Hong Kong and has 1600 kilometers of canals running throughout for water exchange.

The aim of shrimp farming in these countries is not for a protein source but for foreign exchange with the US and Europe. In places where technology is limited and environmental laws are lax, shrimp farming is a lucrative business. The United States imports more than $3 billion of shrimp annually. No other marine aquaculture product comes close. The second most economically important product is salmon, which has a trade deficit of around $500 million.

The externalities caused by salmon and other marine finfish aquaculture are less pervasive, when compared to those of shrimp aquaculture. This is due to several factors: First, marine finfish aquaculture requires less coastal land, thereby reducing user-conflict and habitat alteration. Second, it does not use endless amounts of freshwater, which further reduces competition for resources. Next, it is of lower consumer demand. And last, it requires a greater technological infrastructure, which limits participation in the industry to a selective population.

However, biological pollution, fish for fish feed, eutrophication and chemical pollution are still appreciable environmental externalities of finfish aquaculture. Escaped cultured animals can alter the local biological populations and community, as in the 2000 case in Maine where 100,000 salmon escaped. Using fish protein to cultivate fish can lead to bioaccumulation of PCB, dioxins and other toxins in the fish that we eat. In many cases, the concentration of these chemicals is four or more times greater in farmed salmon than in wild salmon.

In addition, in concentrated animal production operations, antibiotics and other treatment chemicals are administered to keep the animals growing quickly without dying from the pathogen that spreads in the crowded farm. These chemicals find their way not only into the environment but also into the human consumer. Finally, the release of excessive organic materials into a water body can drastically alter the ecology.

So, what seafood is safe to eat and environmentally “friendly” at the same time? Wild-caught fish (or shrimp) from well-managed fisheries, of course.

The problem here is that well-managed fisheries are hard to find. Traditional fishery management in the United States has led to the collapse of many fisheries, such as the infamous New England cod. Fisheries have been managed based on the maximum sustainable yield (MSY), which recommends harvest levels based on historical and non-existent conditions and assumes that the current population size has no effect replacement rate of the stock.

The MSY also fails to account for spatial variability, differential responses in multispecies fisheries and other important and complex ecological interactions. Moreover, extensive monitoring of fishing activities is needed to manage a fishery well, unless you have very honest and regulation-abiding fishermen. Monitoring is expensive, and the quality of data collected is often dubious, as the majority of fishery observers do not fully appreciate the impact of their work.

To manage a fishery sustainably, different maximum sustainable yield charts must take into account the realities of wild fish populations. Academics have been talking of ecosystem-based fishery management (EBFM), where the total biomass removed by all fisheries in a given ecosystem does not exceed the total amount of system productivity. How to delineate an ecosystem and measure system productivity are two issues yet to be answered.

The good news is that the current political climate favors an ecosystem-based fishery management. In fact, Obama’s Ocean Task Force is using ecosystem-based management as the guiding principle in a new era of coastal and ocean management. But fisheries are highly complex, and only time will tell whether EBFM works.

Until then, eat seafood at your own risk.