Aquaculture 2.0

Earthworms are the future of seafood. Not yet, but they will be.

This future is aquaculture. I don’t aim to offend and befuddle fisheries’ scientists and sustainability czars. By free admission, aquaculture’s nasty reputation as a polluting and destructive industry is in many cases deserved. The feces and antibiotic clogged pools of intensive shrimp farming along the coasts of Central America and Southeast Asia, which often supplant great swaths of typhoon-protective mangroves, embody environmentally irresponsible food production. My argument addresses not crustacean but finfish aquaculture, an industry beset by problems similar to those of shrimp farming. What is broken, can and must be fixed. In the optimistic spirit of reform sweeping through American politics, it’s time to reexamine finfish aquaculture and give the ecologically responsible variety, the earthworm variety, a second chance.

Aquaculture is a booming global industry: from 2002 to 2006, world aquaculture production increased from 40.4 million metric tons to 51.7 million metric tons. Over a three-decade span from 1975 to 2005, aquaculture production grew tenfold. During this same span of time, however, wild capture fell from 93.2 to 92.0 million metric tons. The inherent exhaustibility of the oceans necessitates that economically efficient and environmentally responsible aquaculture fill the gap between supply and demand for finfish and shellfish worldwide.

Genetic contamination and pollution, both chemical and biological, are serious blemishes on the face of responsible aquaculture, however, the solution is simple. Floating or land-based solid-wall tanks, such as those already in use in British Columbia, eliminate escapes altogether. Wastes and uneaten feed, all collected within the tank, are pumped through a filter, eliminating their respective eutrophying and polluting effects. The real problem with status quo aquaculture isn’t genetic contamination or pollution, but rather the inefficiency and unsustainability of fishmeal as used for fish feed

Carnivorous finfish aquaculture, the type employed in salmon and tuna farming, typically depends on fishmeal, an oily paste made from ground fishes such as mackerel and sardines, for feed. Each pound of farmed fish for human consumption demands many pounds of fishmeal throughout the farming process, presenting a serious barrier to the expansion of responsible aquaculture. Tilapia, a onetime dining hall staple, is only 25 percent calorie efficient, meaning that it takes four tons of fishmeal to grow only one ton of tilapia. Sardines and mackerel serve as important sources of protein worldwide and as the diet of larger, commercially valuable stocks. New sources of feed must be developed in order to facilitate industrial expansion and ease aquaculture’s strain on the world’s overfished oceans.

Enter earthworms, the sustainable aquaculture feed of the future.

The key to the multi-pronged success of earthworms as aquaculture fodder is their diet of organic wastes. Land-based pollution, such as festering animal poo, is an enormous problem for coastal fisheries impacted by runoff. Britain alone produces 84 megatons of cow manure, 9 megatons of pig waste and 5 megatons of chicken waste each year, much of which flows to the coast as runoff. This pollution is a significant contributor to the declining productivity of wild fish stocks, as fish struggle to cope with their heavily contaminated environment. Earthworms solve this problem by converting land animal wastes into high-protein aquaculture feed. Earthworms convert cow manure into dry matter at a remarkable 10 percent clip, such that Britain’s 84 megatons of cow manure could produce 8.4 megatons of dehydrated earthworms, delivering a protein punch of 5.9 million tons. The recipe is uncomplicated: find crap, add worms, wait, then harvest, dry and grind.

The rock-solid implications of earthworms for aquaculture have already been verified. Two species of worms were fed to a group of trout, a classic intensive aquaculture species, while another group was fed commercial trout pellets made from fishmeal. The results were splendid: the earthworm-fed fish grew as well or better than their fishmeal-fed counterparts. Another study indicated the effectiveness of earthworm feed on tilapia aquaculture, finding that tilapia actually grew better with earthworm supplements than with fishmeal.

Using earthworms as fish feed presents a truly novel method for reducing the impact of aquaculture on marine ecosystems. The benefits are threefold. Earthworms eat polluting manure, improving water quality of coastal fisheries and aiding in recovery from overfishing. Eliminating fishmeal from aquaculture diets will also significantly reduce overall stress on wild fisheries as well as allow for production cost control independent of the price of wild fish. Thirdly, and not insignificantly, earthworms can be used in place of fishmeal to feed land animals such as cows, pigs and chickens. At present, land animal consumption accounts for a great deal of fishmeal intake, and transitioning livestock to an earthworm diet will take huge pressure off wild fisheries. Earthworms are a triple-win solution to intensive aquacultures’ appetite for fishmeal.

The worms are by no means a silver bullet — they cannot solve all of aquaculture’s problems immediately. Pollution from intensive crustacean aquaculture will remain a serious threat to coastal habitats until the lagoons are either moved inland or farmed less intensively. This is to say nothing of mollusk aquaculture, a genuine champion of sustainable protein production. Yet in the realm of tuna, trout and salmon, aquaculture has a new hope — the earthworm.


  • ES ’13

    Thank you for an informative, interesting, and uplifting article!

    I always appreciate learning about interesting ways to solve problems (rather than 90% of YDN, which simply complains about problems).

  • @ ES ’13

    Why don’t you write for the YDN and make it better?

    Funny how you feel you figured out the best college daily a month after you got your IKEA furniture up the stairs in Lawrence.