It's not the rich or poor that poses the greatest threat to the survival of coral reef fishes, but the middle class, according to research published in a recent issue of the journal Current Biology.
The study, by Joshua Cinner and coauthors, found that there was a correlation between low populations of reef fishes and communities that are relatively middle class in Eastern Africa.
At the same time, communities at either end of the socioeconomic spectrum had up to four times larger fish populations.
The authors examined complexity of reef habitats, human population densities, and socioeconomic development among villages in 19 fished and 11 un-fished study sites in five countries along Africa's Indian Ocean coast.
Basing their results on a statistical analysis of the data obtained, the authors explain this trend by the interplay between customary cultural institutions such as taboos and the effect of economic growth on the social fabric of communities.
In poor communities, exploitation of marine resources is kept in check by technological constraints and social institutions.
With increased economic growth comes a reduction in dependency on marine resources, but at the same time, increasing access to technologies (such as engines and spear guns) coupled with an erosion of customary management institutions results in a decrease in reef fish biomass.
One such example is in Kenya, where the breaking down of customary institutions in recent years has led to the adoption of destructive fishing techniques.
The most affluent communities have further decreased their dependence on marine resources and high levels of engagement in salaried employment.
At the same time, access to even more technology such as larger boats that enable fishing much further afield and an adoption of more benign technologies (such as reef handlines) over more destructive ones (such as gill nets) have allowed fish populations to recover.
For more information, see the paper: Cinner, JE, TR McClanahan, TM Daw, NAJ Graham, J Maina, SK Wilson and TP Hughes, 2009. Linking social and ecological systems to sustain coral reef fisheries. Current Biology 19, pp. 206"212.