Calling all Recruits!

Belize has on eof the most diverse fish communities in the world. One cannot even imagine a healthy coral reef structure without the assemblage of vibrantly colored fishes surrounding various corals and associated species. There is no doubt that fishes are the most abundant and conspicuous large organisms inhabiting a reef. How is this possible?

Vibrantly colored fish surrounded by various corals and associated species build a healthy reef.
One of the reasons for the high diversity of species on reefs of course, is the wide range of habitats available in the form of coral, sand areas, caves and crevices, algae areas, shallow and deep areas, as well as different zones progressing across the reef. However, there are four theories claiming that different aspects of recruitment and competition also play a major role in the diversity level of coral reef fishes. These theories are known as the competition model, the lottery hypothesis, the predation- disturbance model, and the recruitment limitation model.

The competition model is the more classical model that states the high diversity is the result of strong competitive interactions that lead to high degrees of specialization. This is to say, that each species has a specific set of adaptations, giving them a competitive edge in at least one scenario on a reef. In other words, these fishes have narrower ecological niches, so more species can be accommodated in a given area.

In contrast to the competition model, the lottery hypothesis insists that fishes are not specialized. Success and persistence results from chance, as to which species of the planktonic larval pool occupies a vacant space. Therefore, competition is unimportant in this case and recruitment dominates.

The third theory, the predation-disturbance model hypothesizes that fish populations do not reach equilibrium at all. Predation, catastrophe, and unpredictable recruitment keep population numbers below the level at which resources or food become limiting. The most recent view, known as the recruitment-limitation model argues that larval supply is never adequate for the adult population size to reach its full potential. The adult population mirrors variation in larval recruitment and not post-recruitment events. Data from an empirical test conducted by Doherty and Fowler in 1994 support this model for the variation in abundance of damselfish. Despite this information however, additional data is necessary for other fishes. As of now, the accuracy in the evidence as to which explanation for coral reef diversity is correct, if any. Although one thing remains clear, fish recruitment to the reef is just as variable as the fish species themselves.

Reef Brief is a weekly column published in the San Pedro Sun

For more information on Green Reef please contact us at (email: or telephone us at 226-2833.

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