August 12, 2013
US scientists develop vegetarian diet for marine fish
Scientists from the University of Maryland Centre for Environmental Science''s Institute for Marine and Environmental Technology have developed a completely vegetarian diet that works for marine fish raised in aquaculture.
The findings were led by Dr Aaron Watson and Allen Place. "Aquaculture cannot sustainably grow and expand to meet growing global population and protein demand without developing and evaluating alternative ingredients to reduce fishmeal and fish oil use," said Watson.
The team has proven that a completely plant-based food combination can support fast-growing marine carnivores like cobia and gilthead sea bream in reaching maturity just as well as - and sometimes better than - conventional diets of fishmeal and fish oil made from wild-caught fish.
Nearly half of the world''s fish and shellfish supply is supplied by aquaculture and scientists have been trying to figure out how to make growing fish sustainable. Many high-value fish such as cobia, sea bream, and striped bass are predators and eat other fish to survive and grow. As a result, their food in captivity is made of a combination of fishmeal and fish oil, and must be caught from the wild to feed them. This is expensive and it further depletes the world''s fisheries.
"This makes aquaculture completely sustainable," said Allen Place. "The pressure on natural fisheries in terms of food fish can be relieved. We can now sustain a good protein source without harvesting fish to feed fish."
The replacement of fishmeal and fish oil in aquaculture diets has been a goal for researchers for decades but has met with limited success. The team''s research centred on replacing fishmeal with a blend of plant protein sources to completely eliminate the need for fishmeal and fish oil in diets for cobia and other high-value marine carnivores.
Fishmeal was replaced with a food made of corn, wheat, and soy. Fish oil was replaced with soy or rapeseed oil, supplemental lipids from algae sources, and amino acid supplements, such as taurine. An amino acid used in energy drinks, taurine plays a critical role in the metabolism of fats, stress responses, and muscle growth, and is found in high levels in carnivorous fish and their prey.
In addition to the potential to turn aquaculture into a more profitable enterprise and ease the pressure on catching wild fish, raising fish on a vegetarian diet also means cleaner fish to eat.