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.

Morris and others 2011
Karapanagiotidis and others 2006

These spicy tacos are sure to be a treat at your next invasivore fiesta!

Ingredients (Makes 6-8 tacos)

1.5 tbsp garlic salt

1.5 tbsp ground cumin

1.5 tbsp chili powder

3 tbsp olive oil

1 small yellow onion, chopped

1 lb wild-caught salmon fillets, skinned and cut into 1″ cubes

1 can (11oz) Green Giant Southwestern Style corn

1 bunch cilantro, chopped

1 lime

1 package tortillas

(Optional) Your favorite taco toppings

Getting ready for some tasty tacos!

Directions

1.  Combine garlic salt, ground cumin, and chili powder in a small bowl; set aside

2.  In a large skillet, cook onion over medium heat for 2-3 minutes or until onion becomes soft

3.  Toss salmon into the spice mix to coat on all sides; add to skillet and increase heat to medium-high

4.  Sear salmon cubes for 3 minutes, being careful to keep cubes moving with a spoon.  After 3 minutes, use spoon to flake salmon apart into large chunks.

5.  Reduce heat to medium, add corn and cilantro, cook for an additional minute

6.  Squeeze the juice of 1 lime into the skillet, mix, and serve in warmed tortillas with your favorite taco toppings.  Suggestions: sour cream, chopped avocado

Completed salmon tacos served with cilantro rice and a lime garnish.

Notre Dame graduate student Peter Levi takes a break from his research on Pacific salmon to tell us about their impacts as well as the impacts of their Atlantic brethren.

Atlantic salmon (Salmo salar) are a popular dinner item from coast-to-coast.  But the number of these fish in the Pacific Ocean may soon outnumber those in the Atlantic Ocean!  That may sound preposterous…or it may simply sound like another case of invasion.

Atlantic salmon are a key aquaculture species, especially off the coast of South America.  Paradoxically, Atlantic salmon are endangered in the Atlantic Ocean, so farming them may be the only way to get them to your plate.  However, these farms come at a cost to native organisms in the Pacific Ocean, including Pacific salmon.

Salmon farms are often densely populated, which may lead to increased diseases and pathogens that could spread to native salmon.  Additionally, escaped Atlantic salmon may bully Pacific salmon out of their native spawning sites.  Finally, although it appears Atlantic-Pacific salmon hybrids are difficult to produce, the fear of genetic interactions between salmon species still looms, especially among locally threatened and endangered Pacific salmon populations.

Why does an Atlantic salmon invasion matter?  Pacific salmon play a key role in their native ecosystems.  When juvenile salmon migrate to the ocean from the stream or lake where they were born, they are often no larger than your finger.  Salmon feed and grow in the ocean for one to six years, depending on the species, putting on many pounds and growing to the length of your arm, but with much more mass.  Pacific salmon only make one return migration to their home stream or lake, dying after spawning and protecting their nests for as long as they still have energy.

Look closely to see hundreds of pink salmon in Maybeso Creek, Alaska. Photo Credit: Peter Levi

Salmon bring literally tons of nitrogen, phosphorus, and carbon with them, which fertilizes plants and animals in and around these freshwater ecosystems, from algae and fish to brown bears and trees (also recall that introduced salmon runs in the Great Lakes can also represent an influx of contaminants).  In contrast to enriching freshwaters, salmon runs can also be a destructive force via upstream migration and digging of nests.  Recent research has shown that stream structure is an important determinant of whether salmon have a net enrichment or disturbance effect on their natal surroundings.  In contrast to native Pacific Salmon, Atlantic salmon will spawn in multiple years before dying, likely having a greater disturbance than enrichment effect since they take their nutrients back to the ocean with them after spawning.  Therefore, if they invade and replace Pacific salmon, the natural ecological dyanmics will be severely disrupted.

With such important ecosystem impacts, it is worth giving some extra thought to sustainable consumption the next time you are planning a salmon meal, whether the Atlantic or Pacific variety.

By far one of the most popular fish consumed worldwide, salmon have been introduced around the world, occasionally reaching invasive status. But not all salmon are created equal.   Below, guest contributor Peter Levi discusses options for sustainable salmon consumption. Peter is a PhD student at the University of Notre Dame whose research focuses on the influence of annual salmon migrations and watershed disturbance on stream ecosystem function.

The many species of salmon

There are seven species of Pacific salmon, five of which spawn in streams and lakes of North America.  These five species have two common names each, which can lead to some confusion (but see table below).  The genus, Oncorhynchus, also includes Steelhead and cutthroat trout.

Pacific Salmon Species; Photo Credit: Wikimedia Commons

Atlantic salmon (Salmo salar) are listed as an endangered species in the United States and Canada.  Despite the listing, Atlantic salmon appear on many menus and fish markets due to their popularity as a farm-raised fish.

Wild-caught vs. farm-raised: it’s all in the label

Salmon are a sustainable fish…for the most part.  Salmon are often well-stocked in grocery stores, from fresh fillets and vacuum-sealed smoked fillets to canned and frozen.  With several species available, being an informed consumer can ensure the salmon fishery continues to be sustainable.

Wild-caught salmon are considered to be the most responsible consumer choice.  Any of the five Pacific salmon species may be wild-caught.  Note that the labels in grocery stores read “wild-caught” and not simply “wild”.  The natural populations of salmon in the Pacific Northwest, British Columbia, and Alaska are intensively managed and supplemented by hatchery-raised salmon (king, sockeye, and coho).  Hatcheries release juvenile salmon into nearby streams and they travel to the ocean, similarly to naturally-spawned salmon.  There is no way to distinguish between the millions of Pacific salmon that were born in a hatchery versus the wild.

Farm-raised salmon are very popular, and their market has been growing along with many other forms of aquaculture in the previous two decades (e.g., shrimp, tilapia).  Since Atlantic salmon are endangered in the US, the fillets on the market are farm-raised.  However, many of these farms are located in the waters off Chile in the Pacific Ocean.  Escaped Atlantic salmon have caused damage to Pacific salmon species and has the potential to establish as an invasive species.

Introduced Pacific salmon also occur in several places around the globe, including the Great Lakes.  King and coho salmon were introduced to the Great Lakes in the 1960s to foster a sport-fishing industry.  The populations are maintained with annual stocking, similar to the wild populations in the Pacific.  Pink salmon also exist in the Great Lakes as an invasive species from an accidental introduction.

As informed eaters, we can choose salmon and other fish species to minimize extinction risk, environmental damage, and by-catch.  For information on salmon and which other fish species are the most responsible dining choices, check out the Monterey Bay Aquarium’s Seafood Watch.