Do Rockfish Act Like Humans in Stressful Situations?
Authors: Elsie Herman, Kaitlyn Meeks, Ryan Ortiz
Rockfish, a diverse range of fish species found in the Northern Pacific, are facing more than just a dinner plate with the rising threats of climate change. From the coast of California up to Washington, rockfish have a lot to worry about as the pH of the ocean has begun to decline, causing waters to become more acidic. Coastal waters undergo drastic changes in pH due to coastal upwelling, a process that allows cold, deep, and oxygen rich waters to move towards the surface pushing warmer, nutrient rich waters deeper into the water column. This alters the pH of the water throughout the water column affecting bottom dwelling creatures such as rockfish. Ocean acidification amplifies these changes due to the reaction that occurs between carbon dioxide and seawater (2). Seawater breaks down carbon dioxide into acidic compounds called carbonic acid that aid in lowering the pH of the water. When increasing the amount of carbon dioxide burned into our atmosphere, much of those emissions end up in our oceans, increasing the production of carbonic acid and consequently aiding in ocean acidification. These changes can alter bodily function in vulnerable organisms such as juvenile rockfish (4).
You’re Not Alone, Rockfish Also Lose All Motivation During Bad Weather (Water).
When it’s cold outside, we love to stay in and lounge around. Rockfish have a similar tendency to slow down when the water is bad. Because they are still developing, increased pH of the water leads young rockfish to change certain body functions such as their metabolism: the build-up and break-down of bodily compounds to create enough energy for the organism to survive (1). During a combination of upwelling events that decrease the amount of available oxygen in the water and ocean acidification, rockfish find it harder to produce enough energy, increasing their metabolism to compensate. This is both exhausting for the fish and causes them to move slower, which compromises their ability to escape predation threats. While hungry predators love the chance to snag an easy meal, rockfish populations are not so happy with these developments. Rockfish can live to be over a hundred years old and do not reach sexual maturity until late in their life (6). With slower moving rockfish being hunted down to small populations, the future of rockfish in the North Pacific is less certain. A reduction in carbon entering ocean systems could aid greatly in helping rockfishes’ metabolism become motivated once again (1) .
Conservation Physiology Journal: https://watermark.silverchair.com/coy038.pdf?
Rockfish Are Having Trouble Getting Their Act Together.
The environment that you grow up in is important. It determines how you act, how you think, and even your personality. The same can be said for rockfish. The environment that they live in can alter their behavior and physiology. A team of researchers collected juvenile blue and copper rockfish and submitted them to treatments of different pH levels over several weeks (3). After that period of exposure, the rockfish were then put through a number of behavioral and physiological tests. That’s like putting several toddlers in stressful conditions and then testing them. Copper rockfish showed changes in behavioral lateralization, which is a bias between turning their bodies left or right (3). Copper rockfish had a right bias. It may not sound so bad on the surface, but it is critical for escape reactions from predators. Say your being chased by a bear and you can only make right turns when running away. Not very effective is it? Copper rockfish also showed a decrease in critical swim speed. This means that they measured the maximum swim speed the rockfish can sustain before getting tired (3). This is quite problematic if trying to escape from a predator. Finally, the copper rockfish showed a decrease in their aerobic scope. An aerobic scope is an organism’s tolerance range. The smaller the scope, the smaller the range. In Contrast, blue rockfish showed little change in behavior and physiology. This is due to where juveniles can be found, in deep benthic regions of the where pCO2 levels are higher giving it a higher tolerance than its copper counterpart (3).
Feeling the Stress? So are Rockfish!
Studies have shown that other animals, even juvenile rockfish, may experience stress in anxiety-inducing situations in a similar manner to humans. GABAa is a chemical in your brain that is supposed to calm your nervous system by preventing excess information from being processed in your brain, so it can focus on what's important (5). However, when rockfish are exposed to stressful living situations like more acidic ocean water, the GABAa receptor in the brain no longer functions, preventing the nervous system from being calmed down. When these fish experience stress due to the lack of functioning GABAa receptors it is shown that they will move into darker spaces to protect themselves. Does this sound like anybody you know? It sounds a lot like humans to me. When I experience anxiety I know that I want to curl up in a ball and hide in my dark room alone. It has been proven that even if these fish have experienced higher stress levels due to more acidic water they can eventually return to their normal selves. While it may take humans a bit longer, as long as the pH levels return to normal for at least 12 days, juvenile rockfish will return to their normal selves (5).
Royal Society of Publishing: https://royalsocietypublishing.org/
Ocean acidification is having negative effects on rockfish. It makes it difficult to obtain enough energy, alters their behavior, and increases their anxiety. It sounds serious, and it is. However, scientists have but scratched the surface, there is still more to learn and a possible solution to the troubles rockfish face. Say you went in for a check-up at the doctors and they found something wrong with you and were able to treat it before it got worse. That what it is for rockfish. There are signs that these problems can be reversible, like stress (5fin). Scientists have found the problem now, which gives us time to find a solution. In the meantime, instead of waiting, we can try to reduce our own CO2 emissions by carpooling or using reusable items. Every small step is a big movement forward.
We would like to thank Andy Murch, Eiko Jones and Plymouth Marine Laboratory for giving us permission to use their photos.
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2. H. Yoon, C. Park, S. Moon, K. Han, H. Suh, Y. An, S. Choi. Comparative stomach contents and growth of the juvenile black rockfish Sebastes inermis reared in illuminated and unilluminated cages. Fisheries Science. 74, 657-661(2008).
3. S. L. Hamilton, C. A. Logan, H. W. Fennie, S. M. Sogard, J. P. Barry, A. D. Makukhov, L. R. Tobosa, K. Boyer, C. F. Lovera, G. Bernardi. Species-specific responses of juvenile rockfish to elevated pCO2: from behavior to genomics. PLoS ONE. 12, 1-23 (2017).
4. S. J. Bobko, S. A. Berkeley. Maturity, ovarian cycle, fecundity, and age-specific parturition of black rockfish (Sebastes melanops). Fish Bulletin. 102, 418-429 (2004).
5. T. J. Hamilton, A. Holcombe, M. Tresguerres. CO2-induced ocean acidification increases anxiety in rockfish via alteration of GABAA receptor functioning. Proceedings of the Royal Society B: Biological Sciences. 281, 1-7 (2014).
6. W. H. Lenarz, T. W. Echeverria. Sexual dimorphism in Sebastes. Environmental Biology of Fishes. 30, 71-80 (1991).
Jones, E. (n.d.). Copper Rockfish Juvenile . photograph. Retrieved from https://www.eikojonesphotography.com/ngg_tag/juvenile-copper-rockfish/#gallery/juvenile-copper-rockfish/4793/cart
Ocean Acidification . (n.d.). photograph. Retrieved from https://www.pml.ac.uk/Research/Research_topics/