Overfishing leads to fewer reef fish species


Fishing for the table and the ornamental fish trade have led to an alarming decline in coral reef fishes in the central Philippines, an area that was once considered the richest in reef fish species.

This conclusion was drawn from a study conducted by scientists from the Philippines and the USA that is to be published in a forthcoming issue of the journal Environmental Biology of Fishes.  
Cleto Nañola, Porfirio Aliño and Kent Carpenter carried out visual censuses in the Philippines from 1991 to 2008 and compared their results to historical records of the region.  
They found that while the historical data showed the Visayas Region (VR) in the central Philippines to be the richest in fish species, this was not supported by their survey data.  
There is indirect evidence to suggest that the VR has undergone recent losses in species richness. The lower species richness counts in the VR occur despite this region having, by far, the greatest number of marine protected areas (MPAs) and a very high percentage of the surveys were conducted in close proximity to the MPAs.
Capture data supports the hypothesis that over-exploitation for both the food and ornamental fish trade have led to this loss in diversity.  
Overfishing for the ornamental fish trade in the central Philippines has also led to a geographic shift in effort to Palawan and Tawi-Tawi provinces in recent years.  
In addition to regular fishing methods with nets, destructive fishing methods (e.g. blast fishing and fishing with cyanide) have further compounded this decline. Both destructive and normal fishing patterns across the Philippines clearly indicate that the VR experiences the most intense exploitation levels in the country. The significantly lower fish species richness further suggests reef degradation.
Another indication that the VR suffers from unusually high habitat degradation is from the high frequency with which the Brown-barred rockcod (Cephalopholis boenak) was encountered, this being a species particularly adapted to disturbed coral reefs. The authors estimate that half a century of exploitation has led the VR to lose an average of 2% of reef fish species richness per decade.
Unless there is a significant change to the current management practices, the authors predict further loss of fish biodiversity in the "centre of the centre" of marine biodiversity.
For more information, see the paper: Nañola CL Jr, PM Aliño and KE Carpenter (2011) Exploitation-related reef fish species richness depletion in the epicenter of marine biodiversity. Environmental Biology of Fishes DOI: 10.1007/s10641-010-9750-6