Can Carnivorous Fish Become Vegetarians?

Written by on October 6, 2012 in Marine Life
Steelhead or Rainbow trout (Oncorhynchus mykiss). Photo credit: USFWS.

Steelhead or Rainbow trout (Oncorhynchus mykiss). Photo credit: USFWS.

A recent study has determined that carnivorous fish are capable of becoming vegetarians.

Aquaculture is growing in order to meet the increasing demand for seafood.  One of the biggest problems with aquaculture is that most of farmed fish are carnivores and require fishmeal and fish oil as feed.  These fish can’t be fed a plant-based diet because they don’t grow as much, are not as healthy and can’t produce healthy offspring.

“The availability of products for animal feed will be a central issue in the coming years,” the author wrote.

In this study, the researchers attempted to turn rainbow trout (Oncorhynchus mykiss) into vegetarians.  To do so, they immediately switched the trout to a strictly plant-based diet and through selective breeding, were able to successfully convert them to a vegetarian lifestyle after only one generation.

The authors wrote that “domesticated populations of rainbow trout have the genetic potential to adapt to major dietary changes.”

They conclude that by combining environmentally friendly and nutritionally balanced vegetarian diets with selective breeding programs, “it would be possible to improve fish welfare and to ease the transition towards a more sustainable aquaculture production.”

To learn more:
Find the results, published on Sept 28, in the journal PLoS ONE: Selection for Adaptation to Dietary Shifts: Towards Sustainable Breeding of Carnivorous Fish

Steelhead/Rainbow trout. Photo credit: NMFS/NOAA.

Steelhead/Rainbow trout. Photo credit: NMFS/NOAA.

Copyright © 2012 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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