Rising CO2 levels could be making fish stupider, causing them to swimtowards predators rather than away from them, a recent study suggests.
The study used farmed fish that live in concentrations of CO2 that are up to 10 times higher than their free swimming, ocean dwelling brethren. Given that CO2 levels in the Earth’s oceans are expected to be 2.5 times higher by the end of this century, the study represents an important insight into what our oceans may look like in the not too distant future. And it seems them may well be full of fish that are just dying to get eaten.
A guy holding a fish. Fish accounts for around 17% of global protein according to the FAO.
Photo by WorldFish/Flickr CC
According to the study’s authors the smell, hearing and vision of fish are all affected by CO2, making the scent of a predator appealing rather than frightening. By disrupting the brain’s signals from sensory organs the fish are left a little confused as to what is friend and foe. Climate driven CO2 also leads the fish to ignore sounds which under normal conditions would warn them of danger.
It seems CO2 turns fish into masochists.
Aquaculture is an increasingly important global food source, particularly given that the oceans are quickly emptying and fisheries are under severe stress. Farmed fish contributed almost half of all the fish consumed in the world in 2012, a figure that’s due to rise to around 60% by 2030.
Although this may seem traumatic for the fish, living a semi-free life only to be eaten, it also presents opportunities for understanding how climate change may affect free swimming fish in the ocean. One of the scientists who conducted the study, Dr. Robert Ellis of Exeter University, says that aquaculture provides an “accidental” long-term experiment to study the effects of climate change on fish populations.
“There is the enticing possibility that fish and shellfish previously grown in high CO2 aquaculture conditions over multiple generations can offer valuable insights regarding the potential for aquatic animals in the wild to adapt to the predicted further increases in CO2,” Ellis explains.
But the study may also be of interest to those in the aquaculture industry, its authors say, as slight increases of CO2 have been shown to stimulate growth in some species of fish.
“This is really important given that aquaculture is the only way we will increase seafood production to feed the growing human population, particularly given wild fish stocks are overexploited.” Dr. Rod Wilson, another member of the research team said.
So as the CO2 in the Earth’s oceans rises the fish may that live there well become stupider, something that their predators will not mind at all. And those condemned to a life in aquaculture may well have their respective containers’ CO2 levels tweaked so that they grow to their optimum size, something that their predators will also not mind. Oh, to be a fish!