Using growth band autofluorescence to investigate large-scale variation in growth of the abalone <Emphasis Type="Italic">Haliotis midae</Emphasis> |
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Authors: | Lee-Anne Proudfoot Sven Kaehler Christopher D McQuaid |
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Institution: | (1) Zoology and Entomology Department, Rhodes University, Grahamstown, 6140, South Africa;(2) Biotechnology and Environmental Specialist Consultancy, PO Box 8241, Nahoon, East London, 5210, South Africa |
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Abstract: | Growth of the abalone, Haliotis midae, was investigated at Port Alfred, on the south coast of South Africa, using both new and established techniques. A new method
for aging animals is described, which makes use of shell autofluorescence under UV light to visualise internal growth bands.
The deposition of growth bands was validated using measurements from shells of known age and, at one site, comparing growth
estimates to those from cohort analysis undertaken at the same site. The new technique is far less time consuming and labour
intensive than previously described methods; it is also non-destructive and proved to have potential for the reliable and
rapid assessment of growth in large-scale studies. Growth of H. midae was also investigated at nine other sites, incorporating the full distribution range of the species. Systematic geographic
variation in growth was observed along the South African coastline. Statistically significant differences existed among sites
in growth rates for animals <4 years and between 4 and 6 years and in the mean maximum sizes attained. Generally, H. midae from the south/southeast coast were found to have faster growth rates, smaller mean maximum sizes and were assumed to attain
sexual maturity (determined in previous studies) earlier than those along the southwest/west coast. The geographic differences
in estimates of growth observed have significant implications for future modelling approaches and indicate that present national
management strategies are not appropriate as they fail to take regional variability into account. |
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