An increase in the ocean's carbon dioxide levels is stressing out fish.
The man-emitted carbon is causing the ocean's pH to drop, which results in increased acidity, a Scripps Institution of Oceanography news release reported.
A research team observed these environmental changes increased anxiety in juvenile rockfish. The team watched captive fish with a camera-based tracking software system. They compared rockfish kept in in normal waters to those whose environment was more acidic.
The team looked out for whether the rockfish chose to swim in light or dark areas, which is an indicator of stress. They found the rockfish in less acidic water swam freely between light and dark water while the other group spent most of their time in the dark. The fish remained "stressed out" for about a week after they were placed back in normal water.
"These results are novel and thought-provoking," Martín Tresguerres, a Scripps marine biologist and study coauthor, said. "Because they reveal a potential negative effect of ocean acidification on fish behavior that can possibly affect normal population dynamics and maybe even affect fisheries."
Tresguerres believes this type of timid behavior could be a handicap for the rockfish, which live in "dynamic" environments such as kelp forests.
"If the behavior that we observed in the lab applies to the wild during ocean acidification conditions, it could mean that juvenile rockfish may spend more time in the shaded areas instead of exploring around," Tresguerres said. "This would have negative implications due to reduced time foraging for food, or alterations in dispersal behavior, among others."
This type of response to stress is believed to link to the the fish's "GABAA" (neural gamma-aminobutyric acid type A) receptors , which also play a role in human stress.
"Behavioral neuroscience in fish is a relatively unexplored field, but we do know that fish are capable of many complicated cognitive tasks of learning and memory. Increased anxiety in rockfish could have a detrimental impact on many aspects of their daily functioning," Trevor James Hamilton, a neurobiologist at MacEwan University and coauthor of the study, said.
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