This study takes short-term fish social behavior into models, which is an encouraging step in the direction of better understanding how fish populations and the ecosystem respond to pressures such as fishing and may ultimately improve decision-making about how to maintain healthy fish populations.
Characterizing such subtle dynamics is a departure from the way ecologists typically model ecosystems, tending to treat on-the-minute decision making as inconequential for long timescales. Gil says: “Under this convention, we tend to treat wild animals as some sort of dumbness “ Wir really buck tradition kind of. And we found that this convention could be far off.”
Gil and his colleagues created mathematical simulations based on the data they’ve gathered from the reef to show how these seemingly inconsequential interactions actually have serious effects on the reef health over long timescales. Gil explains : “You can play with that ecosystem like you would a game. You can put different human-driven pressures on it and observe how it responds. These ecosystem models are extremely valuable because they enable us to understand how these gigantic, complex ecosystems grow and change really long timescales, from decades to centuries, even millennia”
The results are a bit worrying and promising at the same time. In their simulations, the researchers discovered that it is not only the magnitude of a threat like overfishing that damage a reef ecosystem, but the rate of the damage itself. When people remove fish, they remove an invaluable algae control that can go out of hand, entrap corals and kill them. Gil explains that we are also disabling the social influence that these fish had on the other fish in their social network. So those fish then get less information about when it’s safe to go and eat and control these algae. And this feedback has these consequences on the ecosystem level.”
The models of the researchers find that those consequences include ecological collapse if rapid overfishing occurs. On the other hand, you could get to that exact same target level, but slower—and perhaps even slightly slower in some cases, and you can actually preserve the whole system,” says Gil. The whole system can be supported for centuries in the absence of other drivers such as climate change. This whole phenomenon occurs again because of simple individual decision making made by these fish.”
Simply put, numbers provide security in numbers. If you quickly lose these numbers, you quickly lose that security. For herbivores, the more individuals there are, the bolder they become and the more they feed,” says Luiz Rocha, fish curator at the California Academy of Sciences, who studies reef ecosystems but was not involved in this research. If you remove a group of individuals—by fishing or anything else—the fish left will be shyer and less likely to feed, eventually causing the ecosystem to collapse faster than if we considered population numbers only.
Therefore, this new research could help create more sustainable fishing which is good for everyone. If ecosystems are preserved and the species that live there are, you do not destroy a critical source of protein for many people around the world. “In fisheries, a challenge is that our models make long-term assumptions about fish populations that aren’t well matched with the longer timescales of management actions or with the many timescales of fish ecology and biology,” says Meredith Moore, Director of Fish Conservation at the Ocean Conservancy who was not involved in this new work. This study brings short-term fish social behavior into models, which is an encouraging step in the direction of better understanding how fish populations and the ecosystem respond to pressures like fishing, and could ultimately help improve decision-making about how to maintain fish populations healthy.
So that finding Nemo shark Bruce had it half right – fish are friends, not food. Fish are friends with each other by necessity – but only to form a social network that protects them from sharks like Bruce. Maintain those social networks intact, and we might also protect fish from human contact.
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