The Powerhouse of the Ocean: The plight of the forage fish

A few weeks ago, Leigh introduced us to marine food webs: the who-eats-who of the ocean. She told us about commercially important lingcod and rockfish, both of which are voracious predators – meaning they’re pretty high in the food web.

But we’re fishing for a lot of other species, too. The Food and Agriculture Organization (FAO) estimated that over 93 million metric tons of fish were caught for human consumption in 2014.

But what, exactly, are we catching?

forage fish
Examples of forage fish species. Image: USGS

It turns out, that nearly 30% of global fisheries are targeting species that are considered forage fish. These are the small, open ocean species like anchovies, sardines, and herrings, that play a critical role in the marine food web. They are the species consuming plankton and being eaten by large fish, mammals, and seabirds – a crucial link in the transfer of energy within the ocean.

 

Now, you may be wondering why we’re targeting forage fish. When you go out for a nice meal at a fancy restaurant, you’re probably not going to order sardines if you have the option of salmon or swordfish. And while there is a market for human consumption, much of the forage fish catch is used to create fish meal and fish oil.

Fish meal and fish oil? Why?

aquaculture
Aquaculture tanks for young salmon. Image: USDA

We know fish is very nutritious – that’s why we eat it. But it turns out that it’s not only good for humans, it’s also nutritious for livestock and farmed fishes, as well. With the decline of wild fisheries in recent years, increasing attention is being paid to aquaculture – the farming of fish– and for good reason. The global human population is expected to reach 9 billion by 2040. And there is growing concern over how will we feed that many people.

 

fish oil supplementMany, including the Food and Agriculture Organization, believe aquaculture may be the key to providing long-term food security for the world. And currently, fish meal is one of the most nutritious feeds for farmed fish. NOAA estimates that globally, for every 1 metric ton of farmed fish, a ½ metric ton of wild fish was used for its production. That’s a lot of fish meal.

In recent years, we’ve also seen an increase in the use of fish oil supplements. Due to its high concentration of Omega-3 fatty acids, many medical professionals encourage the use of fish oil nutritional supplements. And that oil is predominantly coming from forage fish.

But what does that mean for the fish?

The problem with targeting forage fish is that they’re incredibly difficult to manage. Characterized by boom-or-bust cycles (frequently resulting in population collapses), the population dynamics of these species are notoriously difficult to predict and extremely sensitive to changes in the environment. In a 2015 study, researchers tried to determine how fishing affects these natural cycles and found that when fishing pressure was applied, population collapses were larger and occurred more frequently.

And remember, because these species represent a critical link in the marine food web, what happens to forage fish affects the entire ecosystem.

But it’s not all bad news. The researchers identified a series of management tools that could be used to identify when populations are at risk of collapse. This would allow fishing to continue when stocks are healthy, and prevent fishing-caused collapse when they are at risk.

The punchline: Forage fish are an extremely important component of our ocean ecosystems and can be incredibly difficult to manage effectively. If you eat farmed fish or take fish oil supplements, make sure those fisheries are using sustainable practices. The whales will thank you for it.

whales feeding.jpg
Image: NOAA Ocean Service

For more information on sustainable fishing practices, check out the Marine Stewardship Council or the Monterey Bay Aquarium’s Seafood Watch program.


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