Welcome to our new blog series, Research Highlights! On the second Monday of each month, we will debut newly published fisheries research by our women of fisheries colleagues. If you have research you would like to highlight and share with our readers, please contact us at women.of.fisheries@gmail.com.
Our November Research Highlight:
1Guerra A.S., A.B. Kao, D.J. McCauley, and A.M. Berdahl. 2020. Fisheries-induced selection against schooling behaviour in marine fishes. Proceedings of the Royal Society B 287:20201752.
We’re nearing the end of 2020 and we are still in the midst of a global pandemic. To mitigate the spread of the covid-19 virus, many of us have significantly altered our behavior. Where once we congregated in large numbers to watch sporting events, listen to concerts, and attend gatherings with family and friends, we are now sticking to smaller groupings. We changed our behavior to stay safe.
Well, it turns out fish may not be that much different than us in this regard. They, too, are known to change behavior to better protect themselves. It is estimated that about half of the world’s fish species school for some portion of their lives, primarily as a way to avoid predation. Previous research has shown evidence that this schooling behavior is genetically wired, but new work finds that a fish’s environment may play a significant role as well.
Our world has become increasingly influenced by technology. In many ways, technology has made our lives easier and helped us become more efficient in the work we do. This holds true in the fishing industry as well. Industrial fishing involves large commercial fishing vessels that rely on the use of various technologies, drones for example, to locate schools of fish and gear, such as purse seines, to capture these schools. Often an entire school of fish is captured in a single effort. Although efficient and the source of much of the world’s seafood, there are concerns that this type of fishing may be impacting the sustainability of our marine resources.
Where once schooling was a strategy to reduce predation, technology that helps these fishing fleets locate and exploit large schools has resulted in the opposite. Now, schooling behavior may actually increase predation.
What is a fish to do?
Graduate researcher Ana Sofía Guerra and fellow colleagues at the University of California, Santa Barbara recently published the results of a study1 that modeled the effect of different fishing pressure levels on fish group size. These results provide evidence that group size may be reduced in the presence of mass capture fishing. This could have far reaching consequences to the future sustainability of these fisheries and the marine ecosystems upon which they depend.
Changes in the social behavior of fish, from larger to smaller groups, can result in more time, effort, and money needed to locate and capture enough to sustain the fishery. Over time, the fishery could become less and less profitable, leading to its ultimate collapse. With so many people’s livelihoods dependent on a sustained and thriving fishery, this kind of collapse could be devastating.
From an ecological perspective, change in fish abundance and behavior can also reduce the foraging efficiency of natural predators, from birds to whales and other top predators. In addition to the effects of high fishing pressure on these fishes and ecosystems, there is great concern about significant ecological consequences from fewer fish and smaller group sizes.
The authors, therefore, urge fisheries managers to consider behavioral changes such as sociality in the regulation of these fisheries. We may not know the collapse of the fishery is imminent until it’s too late.
So, to school or not to school?
Until this pandemic is over, I think I will stick to my small group. It may not be a purse seine that worries me, but like fish adapting to mass fishing practices, I am finding there is not always safety in numbers.
The full manuscript can be found and downloaded here: https://doi.org/10.1098/rspb.2020.1752