According to a recent study published in the journal Global Change Biology, rising CO2 levels in the ocean can disrupt the sensory systems of fish and can even make them swim toward predators and ignore the sounds that normally deter them from risky habitats.
According to the marine biologists who performed the study, these abnormal behaviors have been linked to the effect of CO2 on how the brain processes signals from sensory organs. The study was looking into the long-term impact of rising CO2 levels on marine life because current predictions are that levels in the oceans will be 2.5 times higher by the end of this century.
An important element of the study was the fact that the captive fish living in fish farms can serve as a giant long-term laboratory experiment. As a result of the very high stocking densities achieved in most aquaculture settings, along with the methods employed to control pH and oxygen levels, CO2 levels tend to increase dramatically in fish farms – sometimes reaching 10 times higher than that of the wild. Thus, the multiple generations of fish growing in high CO2 farms can offer valuable insights into the potential for aquatic species in the wild to adapt to the changing conditions in the oceans.
The aquaculture industry may actually benefit from these studies by climate change scientists. The abnormal behavior already being seen in wild fish may not matter in farmed fish, as they are provided with abundant food and shelter and have no predators to avoid. The continuing research may allow fish farmers to optimize conditions to improve the growth and health of their fish and to enhance the long-term sustainability of the industry.
Photo, posted September 24, 2007, courtesy of Carrie Kellenberger via Flickr.