This last week I’ve been in Cairns, Australia, in tropical Northern Queensland. I’ve been searching for a prime invasivore target: Tilapia. Tilapia mariae and Oreochromis mossambicus where introduced into Australia several decades ago, and started becoming a problem about 20 years ago. In many areas, these tilapias have come to dominate native fish communities. Alas, it remains a crime in pest-aware Australia to possess tilapia, dead or alive.
In the Cattana Wetlands, both T. mariae and O. mossambicus are well established. Catching tilapia is, unfortunately, not allowed.
I’m not here to harvest tilapia, but instead test a new method for detecting them, environmental DNA, also known as “eDNA.” Using eDNA, it’s possible to detect the presence of invasive species much faster and at much lower densities than is possible using standard methods like nets or electroshocking. This method has recently been used with much success to detect the spread of Asian Carp up the Mississippi river and approaching the Great Lakes via the Chicago shipping and sanitary canals.
We’re testing this new method to try and better understand the distribution of tilapia in Queensland, and hopefully help target control efforts to prevent this species from establishing in Australia’s grand Murray-Darling Basin and the Gulf of Carpentaria, and evaluate how well previous eradication attempts have succeeded.
I’ve just finished up in Cairns, and now I’m off to Brisbane, another epicenter of the tilapia invasion.
Omega-3 fatty acid content of some edible invasive fish compared to other commonly consumed fish. Data compiled from the NYT, Morris and others 2011, and Karapanagiotidis and others 2006.
On the front page of Monday’s New York Times, a remarkable amount of real-estate was was dedicated to “Another Side of Tilapia, the Perfect Factory Fish.” This article does a great job highlighting some of the unintended consequences of the massive surge in tilapia production around the world in the last ten years or so.
In the article, one of author Elisabeth Rosenthal’s main points is that farmed tilapia isn’t as chock-a-block full of heart-healthy omega-3 fatty acids as, well, pretty much all other types of fish people consume. And it got me thinking: What about some of the edible invasive fish we’ve highlighted?
Frankly, the raw omega-3 fatty acid numbers are not encouraging for tilapia and lionfish, but looking great for salmon. It does not mean that tilapia and lionfish are unsafe, only that they are less than optimal. There’s other issues though too. Researchers say the ratio of mega-6:omega-3 fatty acids is a more important measure, which tends to make wild fish more beneficial than farmed fish in general. So it’s more difficult to compare than either my figure, or Rosenthal’s, suggest.
One of the things we can hope comes from this news is that the enormous demand for tilapia, which drives it’s world wide invasion, may begin to abate.
Due to the seasonality of our last featured species, Brassica rapa, it may take me a few weeks to procure some field mustard as it is the end of winter and things have yet to germinate here in northwest Indiana. In the meantime, here’s something tasty you can do with a previously-featured species, invasive tilapia.
Ingredients
2 cups all purpose flour
1 teaspoon salt
1 teaspoon paprika
12 oz (1 can) beer; any kind will work, I used a pale ale from a local microbrew
8 portions of tilapia filets
Salt and pepper
Extra flour for dredging
1 pot of canola oil (sorry, had to sneak this week’s species in here)
Instructions
Heat pot of canola oil to 375⁰F
Combine 2 cups of flour, salt, and paprika
Add beer slowly (it will froth up) and mix (it’s okay if there are a few lumps)
Rinse tilapia and salt and pepper both sides of filet
Lay fillets on a plate of extra flour to dredge, repeat with the other side of filet so that both sides are lightly coated in flour
One at a time, dip fillets in batter and then place in pot of hot oil
Flip after 1-2 minutes or until one side is golden brown (you may allow more time for thicker fillets)
Note: The oil will lower in temperature when things are placed in it so you may have to turn the heat up a little. Remove from oil when both sides are golden brown. Serve with either chips for a fish and chips meal or dirty rice, lime, garlic sour cream, and cabbage for a fish taco feel.
Beer-battered tilapia with dirty rice, garlic sour cream, cabbage, and lime. Photo credit: Sheina Sim
7 – Minimum cold tolerance (in degrees celcius) of the blue tilapia Oreochromis aureus, the most cold-tolerant Tilapia species. Accordingly, Tilapia invasion primarily threatens tropical and sub-tropical ecosystems.
17 – Chapter of the Bible’s Gospel of Matthew (verses 24-27) in which Peter catches a fish with a coin in its mouth. Speculation that this (unnamed) fish was a species of Tilapia has earned the nickname, “St. Peter’s Fish.”
128 – Approximate calories in one tilapia fillet.
322,000,000 – Pounds of tilapia exported from China to the US in 2009.
Far more in the spirit of invasive species awareness than direct management, I bought tilapia for today’s recipe. And in this confession lies the crux of eating invasive species.
Finished Almond Tilapia. Photo A. Deines
Should consumer demand for edible invasives ever reach the fervor required to drive harmful populations to extinction, that same economic force would provide incentives to farm and/or further spread the species in new locations. Much touted as a sustainable alternative seafood, tilapia is a good example of market demand for an invasive species driving it’s invasion.
Without good legislation combating the spread of harmful species like tilapias, invasions will continue to be substantial economic externalities for meals like this. Good legislation, however, begins with awareness. So in that spirit…
Recipe: Almond tilapia
Ingredients
Almond tilapia ingredients. Photo A. Deines
2 tilapia fillets, about 150g (5 oz) each
1/4 cup olive oil
1/4 cup slivered almonds
1/2 cup whole wheat flour
1 lemon
salt and pepper to taste
Directions
Heat olive oil in a large skillet at a medium temperature. While the oil heats, lightly coat the tilapia fillets in whole wheat flour. Briefly saute the slivered almonds, then lay the floured fillets directly on top of the almonds (see picture below). Drizzle lemon juice and some salt onto the fish and cover with a lid.
Tilapia fillets cooking over almonds. Photo A. Deines
Cook for 3-5 min based on thickness of the fillet. The almond slivers should begin to turn brown. Using a wide flat spatula, flip the fillets over while being sure to hold the almonds together with the fish. Cover the skillet again and cook another 3-5 mins, until the thickest portion of the fillet flakes when probed with a fork. Remove the fillets onto serving plates, and drizzle with some more lemon juice.
Finished Almond Tilapia. Photo A. Deines
I sprinkled some parsley onto the finished product for show, and added some salt and pepper to taste. I recommend a steam or stir-fry vegetable side dish, which seasonally offers great potential for it’s own invasivory. White wine is traditional with a white fish, but I had a Bota Box malbec, which was perfect with the earthy tones of the vegetables and the dark roasted almonds.
It’s the middle of winter here in Indiana, making hunting and gathering difficult. So to kick off a week of tilapia, this is one of my favorite traditional Zambian dishes from my time in the Peace Corps and more recently for my PhD research. It’s salty and delicious, but not typically how Americans cook fish.
Pan Fried Tilapia, Traditional Zambian Style
Tilapias are a diverse group of African cichlids. In the last 60 years, many of these species have been moved around the world for stocking, mosquito and aquatic weed control, and aquaculture. The most common tilapia on menus and ice at the grocer is Nile tilapia, Oreochromis niloticus. Increasingly common at meal time, under many circumstances tilapias are considered highly invasive. Native only to Africa, it’s actually very likely that the tilapia Americans consume are farmed in Central America, or China.
Tilapia at the local grocery. Photo credit A. Deines
Indeed, the global market for tilapia is booming. It shouldn’t be surprising then that tilapias have escaped these farms and established feral populations in many countries far outside of their native ranges.
The global tilapia market has also caused Nile tilapia to be translocated within Africa, to regions where it is not native, but where related species do occur naturally. For example, the Three-spot tilapia, Oreochromis andersonii, the focus of my PhD research, which I blatantly plug:
Collection
While I had to go to Zambia to collect tilapia, you can get tilapia at the grocery store, though the economics of this actually promotes tilapia invasion. As an invasivore it’s much better to catch it yourself if you live in some of the many locations where it’s known to have feral populations. For instance, the Mozambique tilapia is essentially the only fish surviving in California’s Salton Sea. Tomorrow we’ll be rolling-out an interactive map to help invasivores find their query.
Tilapia can be caught with a fishing pole using worms but I’ve also had success with spinners. Cast-nets can be effective in areas where tilapias build nests, which are easy to spot. A tilapia nest looks like a mud volcano or caldera sometimes up to meter across. In Zambia, the most effective (but illegal) method of harvest is known as “kutumpula”, where fishermen beat the water to scare the fish into gillnets. Be sure to check into and abide by local fishery rules when you harvest.
Recipe: Traditional Zambian Pan Fried Tilapia
Ingredients:
Frying small tilapia in Zambia. Photo Credit A. Deines
1 whole tilapia, about 100-300g (~1/2lbs)
1 cup vegetable oil
1 cup corn flour
1tb salt
1 tomato
1 onion
Directions
After gutting and scaling the tilapia, make two or three shallow cuts into the flanks of the fish running diagonally down from the base of the dorsal fin towards the belly of the fish (see picture for example). Sprinkle some salt into the cuts, and then lightly coat the tilapia in corn flour. Heat about ½ cm of oil in a frying pan at medium heat until it crackles when a small amount of water is dripped in.
Carefully place the fish into the oil. Fry for up to 10 minutes on the first side, carefully watching the heat, so as not to burn. Yes, this seems a very long time to fry a fish, until the outer layer of flesh is brown and crispy. While the fish is frying on the first side, dice the onion and tomato. Soon after turning the fish, slide the tomato and onion into the oil, alongside the fish and continue frying. Remove the fish from the oil when it is brown and crispy on the second side.
Continue to cook the tomato “soup” and add about ½ tbs salt. Stirring often with a wooden spoon, cook another 5 minutes, homogenizing the soup by gentle mashing. Pour the soup over the fish, and serve. Nshima and “rape”-the leaves of the canola oil plant, Brassica, also invasive in the US- make excellent accompaniments. Though in Zambian culture, it’s always the fish and vegetables that accompany the staple Nshima.
