The market for commercial fishes has increased with the growing human population so that there is now a very large demand for resources on the reef (Hughes et al., 2003). A large abundance of coral reefs have degraded over the past 2-3 decades and this is largely due to human disturbances. In Jamaica, overfishing has caused an extreme reduction in coral abundance from 50% coverage to only 5% in less than three decades (Adger et al., 2005). Figure 14 shows fishing activity over a reef.
Chronic overfishing is an increasing threat due to populations of humans in coastal areas increasing. There has been an observed reduction of large, herbivorous fish stocks due to overfishing. This results in a significant increase in macroalgal species as they are not being grazed down by the herbivorous fish.
The increase in macroalgal species suppresses the recruitment, productivity and survival of coral reefs as the increase in algal blooms smother the corals (Hughes et al., 2007). Therefore, we see an ecological shift from coral reef to algal species (Hughes et al., 2003).
Overfishing is a persistent disturbance that reduces the resilience of the corals, causing them to be weaker and the ability to recover from natural disturbances such as bleaching will be reduced (Holling, 1973). Therefore, there are major implications for the conservation and management of coral reefs and the management and understanding of fish stocks are important in preventing a phase shift in the ecosystem (Hughes et al., 2007).