Kimbe Island. The research was carried out in Kimbe Bay, New Britain in Papua New Guinea, a region of relatively pristine coral reefs where it is proposed to set up a network of marine reserves. IKONOS-2 image
New evidence that networks of marine protected areas (MPAs) can play a big role in protecting threatened coral reef fish and other marine species from local extinction has been found by an international research team.
In a world-first experiment, the researchers used DNA fingerprinting to show that baby orange clownfish have remarkable homing abilities, with many finding their way back to home reefs after being swept out to sea as hatchlings.
In the process they discovered some baby clownfish had travelled to reefs as much as 35 kilometres distant from the reef where they were spawned – a spectacular feat considering they were only a few millimetres in length.
The research was carried out in Kimbe Bay, New Britain in Papua New Guinea, a region of relatively pristine coral reefs where it is proposed to set up a network of marine reserves.
'Basically, we found that MPA networks can help sustain resident fish populations both by local replenishment and by fish larvae coming in from other neighbouring reserves,' says Professor Geoff Jones of ARC Centre of Excellence for Coral Reef Studies (CoECRS) and James Cook University.
'Using their parent’s DNA to identify where they had come from, we have been able to show that about 40 per cent of baby clownfish that settle in a marine reserve are those that have returned home. In addition, the parents within one marine reserve can explain up to 10 per cent of the baby fish settling in reserves 20-30km away.
'This shows not only how effective a marine protected area can be for conserving the breeding stock on a particular reef – but also how important it is to have a network of protected reefs at the right distance which can help to re-stock one another.'
In another first, the team has demonstrated the power of parental DNA analysis for measuring the health and viability of fish populations in marine protected areas.
Because orange clownfish live in sea anemones and because the locations of all the anemone clumps around Kimbe island were known, the team was able to collect DNA from 506 adult clownfish living around the island – which they believe to be its entire population.
They then tested juvenile fish which had recently returned from the open sea and settled on the reef in order to establish their parentage, finding that about 40 per cent were locally-bred while the remainder had come from other reefs.
'This level of recruitment to the home reef was remarkably stable over time. It shows both the value of having a protected area to maintain the local fish population – and also the importance of having a network of protected areas within a range that allows them to replenish one another’s fish populations,' Professor Jones says.
After they are hatched from the egg, the baby clownfish are swept out to sea on the local currents and then spend an average of 11 days trying to make their way back to their home reef or find a new one to settle on. In this time they may travel 20 or 30 kilometres from their home reef as the crow flies – and in one remarkable case, 35 kilometres. This indicates a tiny fish only 5mm long can travel 3km or more a day.
Other species, such as butterflyfish, spend up to 35 days at sea as babies and can potentially cover even greater distances. However, many butterflyfish babies also return to home reefs.
Clownfish eggs are tended by the male until they hatch. After hatching the tiny larvae spend 11 days in open water before they settle into adult habitat on the reef. Photo courtesy of Gerry Allen
The project’s findings support the growing view that a network of marine reserves is more effective for maintaining a diversity of fish and other marine species than a single, isolated park or no-fishing area.
'The current theory holds that even quite low rates of migration between reefs are enough to prevent certain fish species from becoming locally extinct – and this research bears that out,' Professor Jones says.
'Given the mounting evidence worldwide that populations of many small reef fish are under threat, we think parental DNA analysis offers a new tool to help protect them.'
The research was conducted around Kimbe Bay in Papua New Guinea. Photo courtesy of Dr Glenn Almany, ARC Centre of Excellence for Coral Reef Studies
The tiny larvae of marine species such as the orange clownfish use their sense of smell to help find suitable adult habitat. Scientists from James Cook University have found that ocean acidification will impair this sense of smell, which could affect the ability of larvae to find the best habitat to live in. Photo courtesy of Dr Simon Foale, ARC Centre of Excellence for Coral Reef Studies
The report Larval dispersal connects fish populations in a network of marine protected areas by Serge Planes (Perpignan University), Geoff Jones and Simon Thorrold (Woods Hole) is published in the latest edition of the Proceedings of the US National Academy of Sciences (PNAS).