Welcome to our blog series, Research Highlights! On the second Monday of each month, we 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, submit a nomination form!

This Month’s Research Highlight:
Nadler, L.E., M.I. McCormick, J.L. Johansen, and P. Domenici. Social familiarity improves fast-start escape performance in schooling fish. Communications Biology 4, 897 (2021).

Studies have shown that having good friends can benefit our wellbeing by helping us to feel a sense of belonging and purpose, improve our confidence and self-worth, cope with life’s stressors, and a host of other reasons. As a result, people with good social connections tend to live longer, happier lives than those lacking those connections.

But what about fish? 

This month’s research highlight focuses on the social behavior of fish and the influence of “friends” when responding to a predator. Of course, we don’t really know if fish have friends, but we can look at social structure in terms of “familiarity” or how closely fish are associated with each other. To do this, Dr. Lauren Nadler, Assistant Professor at Nova Southeastern University and lead author of the study, chose to work with the blue-green chromis (Chromis viridis). This made for a great study species for several reasons: 1) They are easy to maintain in aquariums only requiring some simple artificial habitat; 2) They are abundant in the Indo-Pacific region and can easily be obtained from different areas, which ensures both familiar and unfamiliar groups of fishes could be collected; and 3) They do not have a hierarchical social structure, with some fish dominating other members of the group. That’s right, no “bullies” allowed here!

In the study, Dr. Nadler and her colleagues, introduced two different groups of blue-green chromis – in essence one group of “friends” and one group of “strangers” – and observed how members of each group reacted to the presence of a predator. The results were very interesting. It turns out that the more familiar group members (the “friends”) responded quicker to the predator, but they also became more uncoordinated than the group of “strangers.” So, I asked Dr. Nadler to explain why. Does it become an “everyone for themselves” scenario, are they in effect working together to confuse the predator, or something else? She explains it like this. “First, when the individuals in familiar groups did their big, dramatic escapes away from the threat, they were swimming at incredibly fast speeds. At these faster speeds, it would be much harder to maintain coordination and cohesion with their buddies, and they may need to spread out a bit to avoid colliding with each other. The unfamiliar groups executed such paltry, slow responses overall that they may not have needed to spread out and do their own thing to avoid collisions. Second, this “everyone for themselves” strategy could work to enhance what we call the “confusion effect”, in which rapidly moving social animals can avoid predation through their rapid movements that make it hard for the predator to hone in on one particular prey to attack. This more disorganized school structure could in theory create even more confusion for the predator than maintaining their organization.” At this point, we don’t know, but these ideas are certainly fodder for future work.

From this research, it is clear that familiarity is an important factor in a social species’ response to an outside threat and likely their survival. Like humans, fish in these social groups rely a lot on their “friends” to alert them more quickly to real outside threats. A lot of energy would be wasted if they (and we) had to assess every threat on our own, real or perceived. If we could focus only on the real, immediate threats and rely on our friends to help us do that, we can spend our energy and time on more important things. Still, there is so much more we can learn about social behavior from fish, including aspects of social communication and preferences and factors influencing them. Specifically, Dr. Nadler plans to continue her social behavior work by investigating some of the theories why fish respond the way they do. “In particular, I would love to better understand how the presence of familiar fish versus strangers alters individual physiology,” stated Dr. Nadler. For example, her previous research found that social fish are calmer when they are with other fish than when they are alone. Would the presence of other fish in general do the same, or do the fish need to be “friends” or familiar with these fish to get that benefit?

Many questions remain in the realm of social behavior, but one overarching theme is that social beings – from fish to humans – are bound by the need of community for survival. As the famous Beatles song “With a Little Help from My Friends” from 1967 plays in my head, I smile in agreement as I sing that line over and over again. Indeed, we all get by with a little help from our friends.

The full manuscript can be found and downloaded here:
https://doi.org/10.1038/s42003-021-02407-4