How Reef Fish Defend Against Predators

The coral reef is a dangerous place for all its inhabitants; most animals live in close proximity to a host of dangers and different kinds of predators. Their survival depends on their defenses and their ability to break the predation cycle. For reef fish, self-preservation tactics range from keeping alert and learning the lay of the land to anatomical adaptations. Reef animals show an incredible array of anti-predator defenses, including spines, agility, camouflage, self-inflation, poisonousness, and mimicry.

How have fish got better at fighting back?

Only fish that are successful in dodging predators get the chance to breed and pass on their genes. Those characteristics that enabled the parent fish to survive are then passed on through the genes to their offspring and so the process of evolution advances in tiny incremental steps. But while successive generations of prey fish become fractionally better able to avoid their predators, the predators respond in kind, producing an “arms race” of adaptation and counter-adaptation. The astonishing adaptations that reef fish show are the results of this process, spanning millions of years and countless generations of fishes.

How do fish break the predation cycle?

Fishe's defenses against predation can kick in at any stage of the so-called predation cycle. Some try to avoid detection by predators in the first place using camouflage or by hiding. Others try to deter predator attack by bluff, by being poisonous or through their behavior. Most fish remain highly alert in the presence of predators, ready to dart away at speed. And if the worst comes to the worst others have evolved armor and spines so that a predator is unlikely to be able to devour them. Here, we consider each of these strategies, looking at the diverse ways in which fish attempt to overcome their hunters.

What about predation in the aquarium?

If all runs to plan, predation ought not to be a concern for domestic animals — or should it? Although this is true, fish in the home aquarium still display the behavior and appearance of their wild ancestors — what may be called the “ghost of predation past.” Clownfish still seek shelter in their home anemone, shrimps still hide among the aquarium decor, and porcupinefish retain their spiky wardrobe. As more and more marine animals are bred and raised in captivity to supply the aquarium trade, we should expect to see some slight changes in behavior.

For example in tropical freshwater fish, which have been cultivated for much longer than most tropical marines, domestication produces fish that are bolder than their wild counterparts and less likely to take fright. Even so, we should remember that predation has had a huge influence on fish for millions of years and it takes more than a few generations for the ghost of its effect to depart.