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Reef Fish populations recovering on Mafia Island

News item submitted by Emily Lewis
News item dated 29 Jul 2010

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Coral reefs are some of the most diverse ecosystems on earth and are home to a great variety of fish. However, many of these species are threatened by destructive fishing practises and over-fishing, as well as the physical destruction of their habitats. Since the film ‘Finding Nemo’ there has also been an increase in demand of many coral reef fish for aquariums. The extreme colouration and patterning on many species of reef fish, which are used for a variety of reasons including camouflage, mating, and protection against predators, unfortunately also makes them extremely attractive to aquarium collectors.

Frontier volunteers who have been working on Mafia Island, Tanzania, have been collecting data on the diversity and abundance of reef fish within the Marine Park. This has been used to compare the effects of the Marine Protected Area (MPA) with the Intensely Fished Areas (IFA) on the west coast of the island. The first results are very encouraging, as they show that fish diversity is higher and fish abundance is almost double within the MPA. This is great news because it shows that the park is having a huge positive impact on the marine environment.

The most abundant fish species were from the Zanclidae family, which includes the surgeonfish, and the Chaetodontidae family, which includes the butterflyfish; both of which are popular aquarium fish. The Chaetodontidae were nearly three times greater within the MPA compared to the IFA. In addition, the Balistidae family, which includes the triggerfish, was found to be six times more abundant within the MPA than in the IFA. Members of this family are key predators of urchins and sea cucumbers, and are therefore critical controllers of bioeroders such as sea urchins. The fact that the abundance of Diadema urchins is much lower inside the MPA is therefore a good sign for the coral reefs.

 

Emily Lewis

Research and Development Intern