Choosing between wild and farmed fish is often a dilemma for consumers because wild-captured fish cost twice as much as their farmed counterparts — a difference that many believe is justified by the better taste and nutritional properties.
However, with wild stocks declining, fish farming, or aquaculture, provides not only a cheaper but also a seemingly more sustainable alternative to open-sea fisheries.
Personal preferences rule at the fish counter. However, experts have used objective methods to judge the taste and nutritional qualities of farmed fish, and their results may surprise some people who spend more for the wild-caught version.
“Fish coming from aquaculture can have more fat, but that’s because they move less and eat more regularly than what they would do in the wild. Apart from that, the nutritional profiles can be indistinguishable,” said Sadasivam Kaushik, founder-director of Fish Nutrition Laboratory at the National Institute of Agronomical Research (INRA) in Bordeaux, France.
When it comes to taste, wild fish usually have more diverse and distinct flavors, depending on the compounds they absorb from the environment, such as bromophenols, which give a distinct “sea” aroma. Many people swear to be able to distinguish wild fish once they are on the plate, but it’s not always the case.
Emilio Tibaldi, a professor of aquaculture at the University of Udine who co-authored a report for the Italian Ministry of Agriculture, added that a panel of tasters he put together for the study could not distinguish between wild and farmed sea bass.
"The most important factor affecting the taste and smell of fish is freshness, which has to do with their storage rather than their origin," Tibaldi explained.
The taste and texture of fish can vary depending on the age and environment. Each species has an optimal age and weight for consumption, and to follow the market’s demand for smaller portions, some aquaculture fish are sold before they develop a full taste. At the counter, therefore, it’s better to spend a little more and buy fully grown individual fish.
Cultured fish have a slight advantage in safety because their life cycle is too short to accumulate marine pollutants such as methylmercury. However, Tibaldi and Kaushik emphasized that both wild and farmed fish undergo rigorous controls and are safe once they reach consumers.
Waste management can be a problem for aquaculture. For example, European Union regulations oblige farmers to follow strict standards to protect the environment and the quality of products as well as regarding the use of antibiotics.
Many people who eat fish may be interested in the content of omega-3 fatty acids. These compounds are essential to the integrity of the cells' membranes and in many other physiological processes, and they are considered beneficial to health.
Some of these “good” fats come from plants. Oilseed crops, for example, are rich in alpha-linoleic acid (ALA), an omega-3 compound. Other essential omega-3s, like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are found only in the aquatic environment and can be obtained from algae — the primary producers — as well as fish and other seafood.
To preserve the natural content of omega-3 oils in fish, farmers need to balance the diet of their stock carefully throughout the life cycle, Kaushik said. Typically, feeds are a mixture of vegetable proteins, with fish meal and fish oil obtained from capture fisheries. Fish oil, which provides the omega-3s, is becoming a precious, limited resource.
Worldwide, close to 18-20 million tons of fish (about 12% of the global fishery production) are captured each year and transformed into fish meal and fish oil, contributing significantly to reductions in wild stocks. With double-digit growth in demand from the aquaculture sector every year, this rate is hardly sustainable.
The European project ARRAINA, which Kaushik coordinates, is testing ways to lower the amount of fish-derived feeds in aquaculture. Among other things, the researchers found that it is possible to reduce fish meal and fish oil in diets by as much as one-fifth — by substituting them with vegetable feeds — without affecting the health, growth and nutritional value of many species commonly farmed in the EU.
These results are important, but they may not be enough, given the staggering growth in global aquaculture. Therefore, researchers worldwide are trying different ways to substitute fish oil entirely with other sources.
In 2014, the U.K. government approved a trial to feed salmon camelina seeds genetically modified to produce EPA and DHA. Another alternative is growing microalgae to extract the omega-3s, although the costs are still prohibitive, Tibaldi said.
A further strategy is to genetically modify fish so they can produce EPA and DHA starting from ALA, which can be supplied by terrestrial plants. “Freshwater species can naturally synthesize EPA and DHA from ALA. This capability is lost in marine species, but it's still coded in their genome,” Kaushik added. "The technology to induce this production is within reach. However, many people still oppose (genetically modified) products."