Bumphead parrotfish 'like elephants'
Researchers have compared bumphead parrotfish to elephants in that both species can be destructive to ecosystems, but also reshape them.
Asking whether bumphead parrotfish had a positive or negative impact on coral reefs, University of California Santa Barbara's Douglas McCauley, Assistant professor in the Department of Ecology, Evolution and Marine Biology, observed and tracked bumphead parrotfish at remote locations in the central Pacific Ocean.
He spent up to six hours a day swimming with the fish. 'It was one of the more exhausting but wonderful experiences I've had as a field scientist,' he said. The result, which found the parrotfish had both a positive and negative affect on coral reefs, was published in the journal Conservation Biology.
Eating more than 2 tonnes of coral a year, bumphead parrotfish can reduce coral's abundance and diversity, leaving huge scars on large corals and completely devouring smaller colonies. A school of the fish can also excrete up to 50 tonnes of sediment a year, which can contribute to smothering corals.
On the other hand, bumpheads reduce the prevalence of fast-growing algae that can compete with coral for light and space. And when feeding, the parrotfish can disperse coral fragments around the reef, which grow into large colonies - much like birds dispersing seeds.
'The case of the bumphead parrotfish is analogous in interesting ways to the African elephant,' McCauley said. 'African elephants are a vulnerable and imperiled species that can be agents of deforestation and reduce regional biodiversity. These effects are particularly strong in areas where elephants have been artificially confined in high-density aggregations. Science that describes how elephants reshape ecosystems can help managers more effectively approach the complicated task of reversing severe global elephant declines while protecting local ecosystems. Bumphead parrotfish are to coral reefs what elephants are to African savannas.
'Most species do things to ecosystems that we would construe as both positive and negative. Endangered species are no different from their more abundant counterparts.' So just because these fish can be destructive, that doesn't mean we shouldn't protect them.
'We can, in fact, strengthen the integrity of the field of conservation biology by being rigidly objective about the observations we make in nature – even if this means reporting occasionally that rare species can damage ecosystems,' he said. 'If anything, better understanding the full complement of ways that at-risk species use and affect their environment empowers us to more effectively protect them.'
Bumphead parrotfish: The facts
- Can grow to more than 1.3m (4ft) long
- Weigh more than 46kg (100lb)
- Live between 1m and 30m deep in the western Pacific and Indo-Pacific
- Sleep in caves at night
- Schools of bumpheads can contain up to 75 individuals
- One fish eats 2 tonnes of coral a year
- Fish use their heads to ram coral to break it into small pieces