Tackling the Issue of Seafood Sustainability

By Kim Roth 

If you've ordered salmon or shrimp at your favorite restaurant - or prepared seafood at home - chances are you've eaten catch from an aquatic farm. Nearly half of all seafood consumed today is farmed, in part because the per capita demand has doubled since 1950. (During roughly the same time, the demand for grain has increased 40 percent.) If seafood consumption continues to climb - and there are no indications it won't - increased demand will need to be met by aquaculture rather than natural stocks.

No Easy Answers

Aquaculture, the cultivation of aquatic animals and plants in natural or controlled environments, has a number of potential obstacles, said Jim Diana, the primary investigator and leader of the multidisciplinary team from the School of Natural Resources and Environment and the College of Engineering. (See sidebar: The Multidisciplinary Team.)

"Deforestation of coastal areas, the release of chemically polluted wastewater and the escape of exotic species, for example - all of them can harm native fish stocks," Diana said. "But people need to eat. So we have to ask ourselves some hard questions. For example, is the production of food from aquaculture worse than producing it through other techniques? Which affects the environment less - aquaculture or growing corn in Iowa? Those are hard questions."

Diana and his team plan to find the answers. "We've put together an ideal team for this," Diana said. "To do a good integrated assessment, you have to be careful that each component is being analyzed and analyzed well. So we're involving experts in each area - it's not an option; it's critical in order to make the results realistic."

The group will analyze energy, material and economic characteristics of the lifecycle of shrimp culture and develop mass-balance models for an outdoor pond system (the conventional model) and an indoor, recirculating system. (Mass balance is an accounting of material entering and leaving a system. A fundamental principle of mass balance is that matter can't disappear or be created.) The Graham Environmental Sustainability Institute presented a two-year grant for these studies.

A Multi-Faceted Approach

Diana said that the project has many aspects to it. "We're working to develop results that will give us relatively clear measures of sustainability from a variety of perspectives," he said.

The studies will include an examination of the technology, its energy consumption and the control of metabolites and nutrients in the water, among numerous other variables. The team will take a look at microbes in each system to determine how they maintain water quality. They'll compare the sustainability and environmental impact between two shrimp aquaculture systems suitable for use in the United States, particularly inland areas. One assessment will integrate information about energy, materials and the effect on greenhouse gases. And they'll assess the amount of energy that powers various activities, from shipping feed to the farm, to the marketing and distribution of the shrimp crop.

Lutgarde Raskin said her group of environmental engineers felt that, in thinking about a sustainable aquaculture system, "the logical thing is to focus on a closed-loop system so there's no pollution. There are a lot of similarities to treatment strategies we would use in other systems. (Aquaculture) was a natural for us, although I don't think too many environmental engineers have worked in this area."

Realistic Expectations

Diana acknowledged that putting the team's findings into terms and metrics that can be compared presents a challenge. "If a fish escapes from an outdoor farm, how do you think about that? It's a risk, and it could have an effect on native populations, but how do you put it in terms of financial or energy cost?"

The implications of the methodology they'll develop promise to be significant, however. "What I see as our future is an approach to comparing largely different systems in a way that's more or less objective," said Diana. That might include analyses of aquaculture compared with wild fisheries, the aquaculture of two different fish stocks, or the comparison of aquaculture to agriculture. "All are needed comparisons," he said.

"To think you're going to find the perfect sustainable technology is probably foolish at this point," Diana said. "To think we can make different processes more sustainable - that we can probably do. But it requires an idea of how to compare the possible solutions." - E