October is National Seafood Month and this week we're exploring aquaculture - also known as fish farming - through the lens of sustainability. Aquaculture has been around for centuries and, in some locations, has grown into an unsustainable industry. If, as predicted by the UN, we're going to increasingly turn to fish to meet the protein needs of our rapidly growing, global population, it's time to take a fresh look at how we can produce fish in a way that is safe, plentiful and less damaging to the environment. This week's Real Food Right Now is focused on tilapia, a fish that is common in aquaculture systems.
If tuna is the chicken of the sea, then tilapia must be the instant ramen. Tilapia, the common name for nearly a hundred species of cichlid fish, is seemingly everywhere. Over the past decade, this inexpensive mild white fish has popped up on grocery store shelves, restaurant menus, school lunch lines and hospital trays all over the country. Sales of the fish quadrupled from 2003-2007, making it the 4th most consumed seafood in the US. But where did these fish come from? Are they healthy? Sustainable?
A Brief History
Tilapias are native to Northern Africa and the Levant region and have been an incredibly important fish for small-scale fishermen there for millennia. Known as musht or St. Peter's Fish in ancient Israel and the surrounding area, they were one of the three main types of fish caught by artisanal fishermen in Biblical times in the Sea of Galilee.
Tomb paintings dating back to 2,500 BC tell us that tilapias have been farmed and harvested from ponds in Egypt since the beginning of written history. Tilapia mothers carry their babies in their mouths after hatching to protect them from harm, leading the Egyptians to associate them with reincarnation and fertility goddess Hathor. Ancient Egyptians also believed tilapias accompanied and protected the sun god on his daily journey across the sky. As a result, tilapia imagery can be found all over Egyptian artifacts from hieroglyphics on tomb walls, vases and other tilapia shaped amulets and even on burial shrouds.
- Tilapia appear in spell 15 of the Book of the Dead which reads, "You see the tilapia in its [true] form at the turquoise pool", and "I behold the tilapia in its [true] nature guiding the speedy boat in its waters."
- The name "St. Peter's Fish"comes from the story in the Gospel of Matthew about the apostle Peter catching a fish with a coin in its mouth in the Sea of Galilee. The passage reads, "But, lest we cause them to stumble, go thou to the sea, and cast a hook, and take up the fish that first cometh up; and when thou hast opened his mouth, thou shalt find a shekel: that take, and give unto them for me and thee." (Matthew 17:27)
- The word "tilapia" comes from a Latinization of the Tswana word thiape which means "fish."
- Commercial tilapia farmers use testosterone to reverse the sex of newly spawned females to eliminate their presence in the population and ensure that all their fish are male. Because tilapias are prolific breeders, having females in a tank leads to rapid increases in the number of small fish, rather than allowing farmers to maintain a stable population of more robust, harvest-size fish.
Several different species of tilapias are cultivated for commercial use. Larger species of tilapias from North Africa like Blue Tilapia and other wild hybrids like the Rocky Mountain Whites are generally raised in tanks, ponds and aquaponics systems as a food source because they grow quickly and can be densely stocked. Smaller West African species are generally raised to be decorative aquarium fish because they have attractive patterns and tend to play well with other types of fish, unlike their larger northern cousins.
In nature, tilapias are mainly freshwater fish that live in shallow streams, ponds, rivers and lakes. The hardy fish are also able to survive in brackish bodies of water like the Salton Sea, a long forgotten lake in California that's so salty that it kills marine fish.
Today, these fish are of increasing importance in aquaculture and aquaponics. Tilapias eat mostly plant-based diets which make them incredibly inexpensive to farm. Their vegetarian diet also takes the pressure off of wild caught prey species and eliminates the risk of the fish accumulating high levels of toxins like mercury that concentrate in fish higher up in the food chain. Larger species of the fish are often raised for food in large tanks because they grow rapidly and tolerate crowded conditions and poor quality water. Because of these characteristics, tilapias have become the focus of large scale commercial fish farming operations in Papua New Guinea, China, Egypt, Indonesia, Vietnam and the Philippines.
Tilapias are second only to carp as the most commonly farmed fish in the world. In 2012, over three and half million metric tons of tilapia were produced worldwide (that's almost eight billion pounds). Today, 78 percent of the tilapia imported to the US comes from large-scale farms in China. The US produces around 28 million pounds of tilapia per year, about a billion dollars worth.
Tilapias are warm water fish and can't survive in outdoor ponds in places with cold winter months. In the southern United States, tilapia production in outdoor ponds begins in the spring and ends in the fall when the fish are harvested. Tilapias can be harvested at the end of the season or whenever the fish get to a desirable size. Indoor cultivation of tilapias in warm water recirculating tanks can extend the growing season of the fish throughout the year.
Tilapias' scrappy nature and preference for weeds, algae and insect larvae have made them the perfect biological weapon against other aquatic pests. In Kenya, tilapias were introduced as a biological control for malaria-infected populations of mosquitoes. The fish consume mosquito larvae, helping to reduce the number of adult insects carrying the deadly disease. In Israel, hundreds of thousands of tilapias have been introduced into local freshwater lakes where they are expected to act as bio-filters that boost diversity and balance out the lakes' ecosystems by clearing out toxin-producing weeds. In Phoenix, Arizona and Thailand, tilapias have been introduced into ponds and canal systems as a means to control the growth of algae and purify the water without the use of harmful chemicals and herbicides.
However, according to WWF biologist Aaron McNevin, the widespread use of tilapias in poor countries to control weeds and mosquitoes "may not have been the best idea." Tilapia's aggressive feeding and breeding have made them a problematic invasive species. They've spread widely beyond their points of introduction in many fresh and brackish tropical and subtropical habitats around the world and often significantly disrupt native species. This has earned tilapia a spot on the International Union for Conservation of Nature's 100 of the World's Worst Alien Invasive Species list. In the US, invasive tilapias are found all over the south, especially in Florida, Texas and North Carolina where they survive in lakes, streams and the warm waters around power plant discharge zones.
In addition, there's a lot of concern over the environmental impacts of poorly regulated large-scale tilapia farms in China and Central America. Tilapias in China are sometimes raised in water that is contaminated with raw sewage, industrial waste and pesticide-filled agricultural run-off. To make matters worse, these farms turn around and discharge polluted wastewater, further contaminating the local water supply. Farmers in China have been documented mixing illegal veterinary drugs and pesticides to deal with the toxic water, and these pharmaceuticals leave carcinogenic residues in the seafood, posing a serious health risk for consumers. Researchers studying a small tilapia farming operation in Nicaragua found that one pen full of the fish destroyed the entire ecosystem of a pristine lake, killing all of the important aquatic plants other fish species relied on.
When shopping, Monterey Bay Aquarium recommends selecting tilapias raised on farms in the United States and Canada or from closed tanks and in ponds in Ecuador as they tend to be the most sustainable production methods. If those aren't available, tilapias farmed by Regional Springs in Mexico and Indonesia in net cages are good alternatives. The Monterey Bay Aquarium also saysthat typically, tilapias raised in ponds in China and Taiwan are also ok to purchase from a sustainability perspective, as long as you are aware of the concern over the use of chemicals and waste management at those facilities.
What to look for
If possible, it's best to purchase live tilapias from clean clear tanks, so you know they are fresh. Pick one that looks lively, not one that's floating or motionless. If live fish aren't available but the store is selling whole fish, check out the eyes to make sure they look clear - slimy, filmed-over eyes are a sign that the fish isn't fresh anymore. Also, the gills should be clear of dirt and bright red in color, and the scales should be clean and shiny.
If live or whole fish aren't for sale in your area, purchase tilapia fillets that have been recently harvested, look moist and ideally are packed in thin layers of ice. Make sure to smell the fish before buying it - if it has a fishy or musty smell, it's probably not fresh. Tilapia should smell slightly sweet and appear uniformly white or have a slight pink tinge. Also, make sure the fillets aren't sitting in excess water because the fish will absorb flavors from any liquid it's sitting in. Seem like a lot to remember? Here's a handy guide that summarizes all this info with nice illustrations.
Nutrition and effects on the body
There's been a lot of discussion about the nutritional value of tilapias over the last few years, with some even declaring that the fish is worse for your health than bacon. Like all fish, tilapias are low in saturated fat, calories and carbohydrates. However, unlike predatory fish like salmon and mackerel, farmed tilapias eat mostly corn and soy which lacks the fish oils and healthy omega-3 fatty acids that medical research has shown improves heart health and assists in brain development. According to Edgar R. Miller of John Hopkins University, these nutrients are the main reason that doctors and nutritionists are recommending people eat more fish in the first place. Farmers can add omega-3 supplements to their feed to increase levels of these compounds in the fish, but the additives tend to be expensive and can create more pollution.
On the bright side, tilapias do have higher levels of omega-3s than either mahi mahi or tuna and tends to have very low levels of mercury because they are fast growing, have short life spans and eat a vegetarian diet. The fish also offer 26 grams of protein per serving, about half your daily requirement. Tilapias also contain important nutrients like calcium, magnesium, phosphorous and potassium.
What to Do with It and Cooking
If you aren't able to use your tilapia within a day or so of buying it, you can freeze it to extend the fish's shelf life. Just make sure you remove all the air around the fish by either glazing it with water, wrapping it tightly in saran wrap or vacuum sealing it. For the best flavor, try to use the fish within 6 months of freezing.
Tilapias are very versatile and work well in almost any recipe calling for a mild white fish. We've included a list of delicious tilapia recipes below that will warm you up this fall. Bon appetit!