Coral reef fish – Butterflies of the oceans

Butterfly fish (Family Chaetodontidae) are one of the most conspicuous of the fish species inhabiting coral reefs worldwide, due to their beautiful colour, distinctive markings, morphology and interesting social behaviour. Butterfly fish species remain close to coral reefs all their lives as research shows these fish depend on coral species and other reef organisms for food, habitat and protection from predators. Generalist feeders (that rely on a variety of food sources in addition to coral species) are less common than butterfly fish that consume only corals and experience slower growth rates than their corallivorous counterparts.

Butterfly fish swimming in its coral reef habitat. Photo © Anje Ranneberg

Interestingly, some butterfly fish species have a preference for a particular species of coral so their habitats location might be linked to the type and amount of coral substrate present at various locations along the reef. The reefs exposure to the currents and the protection it provides against egg predators might also be reason’s influencing fish preference for a location over other sites. Studies have revealed some butterfly fish species have a home range they explore to forage for food.

As juveniles, butterfly fish have been observed to find a monogamous mate. This type of pairing early in development decreases the stress levels experienced by these fish, for example, they expend less energy defending their home range or competing with other butterfly fish to reproduce. The constraints that solitary fish or fish living in a harem experience, may play to their favour. Female territories have been observed close to the male, which allows the male to protect and maintain his territory, resulting in less energy being used, much like the monogamous pairs but with multiple chances for fertilising opportunities.

Coral reef habitat. Photo © Vincenzo Piazza 

Butterfly fish use complex forms of social and mating behaviour to exploit the ecological advantages available on the coral reef. Their courtship patterns are an interesting window to their survival. Some butterfly fish mate before sunset. This timing reflects their natural behavior but also increases the chances of egg survival from predation by other fish. Some rogue male butterfly fish are opportunistic and intrude on a spawning monogamous pair by attempting to fertilise the female’s eggs with their own gametes.

Once the eggs of butterfly fish hatch, larvae usually settle close to their native spawning grounds, but this can be a temporary strategy to avoid predators or to find food quickly while migrating to another site. Many view habitat destruction from storms and cyclones negatively, but in the marine environment they have a positive affect, because the amount of coral reef refuge for butterfly fish larvae to settle in increases.

Colour might also be a reason for the success of butterfly fish in coral reef environments. Butterfly fish species are well known for their beautiful markings, which might protect individuals from attack by their counterparts or assist mate recognition. Other cues butterfly fish use to identify their mates from other fish are the sounds they make, for example, some make grunting noises while others slap their tails. So a combination of colour and sound cues improves the success of mating, territorial protection and defence against predators. 

Butterfly fish are linked to coral reefs through their colour, morphology, social behavior, courtship, mating patterns and the sounds they make. Their dependence on coral species for food, protection and recruitment, highlights their potential as a coral reef health indicator species. Coral species are experiencing declines from the effects of warmer oceans, smothering from sediment, disturbance from infrastructure development and fishing pressures.

Green sea turtle swimming off the Hawaii Islands. Photo © Chris LaCroix

A combination of all these factors and pressures from the natural environment are creating extreme conditions coral species cannot withstand for long periods of time. Although present studies are working to identify tolerant species of coral that cope with more hostile environments, alternative methods can also be pursued, by protecting coral reefs through expanding marine parks and reducing the activities that are causing their decline both in the marine and terrestrial environments.

Research studies provide evidence of how coral reefs, other marine habitats and associated plants and animals are being affected. These studies have not just been completed in the last few years but over centuries. Considering the weight of evidence that is available to read; and the benefit provided by the natural environment, you have to wonder why the facts presented by scientific research to reduce negative activities are continually being ignored.

Butterfly fish are more than just a fish species swimming around coral reefs, they have developed different ways to communicate with one another, using colour, movement and sound, creating an unforgettable panorama of beauty on many levels.

Written by Gabrielle Ahern

Salty Wave Blue – Into all things ecology.

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