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Caribbean reef fish in decline

Equetus punctatus by Laszlo Photo, Creative Commons.

Scientists have found that the numbers of reef fish are declining in the Caribbean.

By examining data from over 300 different coral reefs they have discovered that densities which have been stable since 1955 have been declining since 1995 at a rate of 2.7%-6% loss each year.

The worst hit groups of fish are the herbivores, invertivores and generalist carnivores - piscivorous, omnivores and planktivores showed relatively little change, if any.

The decline of the herbivorous fish is of special concern as these are the fish that maintain the algae at low levels which in turn helps coral recruitment and survival.

Quoted in Science Daily, Michelle Paddack of Simon Fraser University in Canada said "We were most surprised to discover that this decrease is evident for both large-bodied species targeted by fisheries as well as small-bodied species that are not fished. This suggests that overfishing is probably not the only cause."

Instead the study suggests that the overall cause is the relatively recent degradation of the local coral reef. Coral reefs in the Caribbean have declined massively since the 1970s with an overall 80% reduction in coral cover.

This is due to a number of factors, including the rise in ocean temperatures, coral diseases, and an increase in sedimentation and pollution from coastal developments.

In other geographical areas where there have been coral reef losses, there has been a lag of about 5-10 years from decline of coral to decline in the numbers of the reef fish.

However here we see a lag of at least 15 years. This is probably due to the ability of Caribbean reef fish too use other non-coral habitats for breeding and speciation and the fact that no Caribbean reef fish feed exclusively on coral.

This delayed lag does mean that we now have to deal with problems that occurred years ago.

Paddack said her study, which involved a team of scientists from the UK, Cuba, USA, Costa Rica and the Caribbean, should serve as a call to action.

"If we want to have coral reefs in our future, we must ensure that we reduce damage to these ecosystems," she said.

"On a personal level, this may mean not buying wild-caught aquarium fish and corals, not eating reef fish species that are declining, taking care not to anchor on reefs, and reducing our carbon emissions to help control climate change.

"But importantly, we need to let lawmakers and resource managers know that we care about these ecosystems and we need to push for changes in how they are managed."

Practical Fishkeeping will be covering the plight of coral and reef fish in more detail in the June issue of the magazine.

For further information see: Paddack et al., Recent Region-wide Declines in Caribbean Reef Fish Abundance, Current Biology (2009), doi:10.1016/j.cub.2009.02.041

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