|The ecological implications of small body size among coral-reef fishes|
Munday, P.L.; Jones, G.P. (1998). The ecological implications of small body size among coral-reef fishes. Oceanogr. Mar. Biol. Ann. Rev. 36: 373-411
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
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Small species (<100 mm total length) are a diverse and abundant component ofcoral-reef fish assemblages. However, difficulties identifying and estimating theabundance of small species has meant that they are often ignored or undersampled in community level studies. We use studies that sampled whole assemblages inorder to examine size/diversity and size/abundance patterns within coral-reef fishassemblages. We then examine body size in relation to patterns of habitat use, species interactions (competition and predation) and life histories of coral-reeffishes. Species diversity (typically peaks in small size classes (<100 mm) and thereare many low diversity larger size classes. In some assemblages, diversity alsodeclines among the smallest species (<50 mm). the high diversity of smallcoral-reef fishes may partly be attributed to the complex structure of coral reefs.However, we find no evidence that diversity/size distributions are controlled byincreased availability of niches or greater living space for small fishes.Regional-scale processes also influence local diversity of coral-reef fishes. Inparticular, high rates of speciation among small species might contribute to theobserved diversity/size distributions. Declines in abundance with increasing bodysize have been attributed to equal partitioning of energy among species of differentbody sizes ("energetic equivalence rule"). We find no support for the "energeticequivalence rule" in assemblages of coral-reef fishes. Although body size wasgenerally a poor predictor of abundance for coral-reef fishes, the upper bound ofthe size/abundance distribution was very uniform among the assemblage weexamined. This upper bound may prove useful for selecting species most likely tobe resource-limited. Small species of coral-reef fishes are more closely associatedwith the reef matrix than their larger counterparts. We propose that this is largelythe result of high predation risk for small species. It is generally believed thatsmaller species and smaller size classes within species are subject to highermortality rates. However, further studies are required to test this assumption. Thediversity and abundance of small reef fishes, and their restriction to specializedhabitats may increase the likelihood of competitive interactions. There is ampleevidence of intraspecific competition among individuals of similar size in smallcoral-reef fishes. There is less evidence of interspecific competition amongcoral-reef fishes. However, the outcome of interspecific interactions will, in part,depend on the relative size of species. Because body size can influence theintensity with which predation and competition act, consideration of populationsize-structure may help develop multifactorial models of population dynamics ofcoral-reef fishes.