Abundance and demography of a seasonal aggregation of zebra sharks Stegostoma fasciatum

Dudgeon, C.L., Noad, M. J. and Lanyon, J.M. (2008) Abundance and demography of a seasonal aggregation of zebra sharks Stegostoma fasciatum. Marine Ecology - Progress Series, 368 : 269-281.


Author Dudgeon, C.L.
Noad, M. J.
Lanyon, J.M.
Title Abundance and demography of a seasonal aggregation of zebra sharks Stegostoma fasciatum
Formatted title Abundance and demography of a seasonal aggregation of zebra sharks Stegostoma fasciatum
Journal name Marine Ecology - Progress Series  (ERA 2012 Listed)    (ERA 2010 Rank A)   Check publisher's open access policy
Publication date 2008-09
Sub-type Article
DOI 10.3354/meps07581
Volume number 368
ISSN 0171-8630; 1616-1599
Start page 269
End page 281
Total pages 23
Place of publication Germany
Publisher Inter-Research
Collection year 2009
Language eng
Subject C1
960808 Marine Flora, Fauna and Biodiversity
060205 Marine and Estuarine Ecology (incl. Marine Ichthyology)
Abstract Seasonal aggregations commonly occur in the marine environment where typically wide-ranging organisms come together to exploit temporary resources or find conspecifics for mating events. The zebra shark Stegostoma fasciatum is a demersal carpet shark that aggregates over the austral summer months in the coastal waters of southeast Queensland, Australia. This study employed photo-identification and mark-recapture methods over a 3 yr period (2003 to 2006) to investigate the population size and structure of this aggregation. In total 327 individual zebra sharks were identified from 570 photographs. Numbered dart-tags on 15 zebra sharks were used to confirm that pigmentation patterns were unique and persistent in wild zebra sharks for up to 810 d. Pollock’s robust design resulted in an annual population estimate of 458 individuals (95% CI = 298–618). The mean number of zebra sharks observed on a single day was 8 (± 8 SE) and the maximum number of zebra sharks seen on a single day was 34. In total, 27% of the sharks were sighted in more than one summer aggregation period and males had greater re-capture probabilities than females. The aggregation consisted exclusively of large (>1800 mm total length) adults with an overall female sex bias of 3.8:1 though sex-ratios varied temporally. Predictable visitation of large, presumably mature individuals to the site raises conservation concerns if aggregations of similar size and structure occur in regions where zebra sharks are fished.
Formatted abstract Seasonal aggregations commonly occur in the marine environment where typically wide-ranging organisms come together to exploit temporary resources or find conspecifics for mating events. The zebra shark Stegostoma fasciatum is a demersal carpet shark that aggregates over the austral summer months in the coastal waters of southeast Queensland, Australia. This study employed
photo-identification and mark-recapture methods over a 3 yr period (2003 to 2006) to investigate the population size and structure of this aggregation. In total 327 individual zebra sharks were identified from 570 photographs. Numbered dart-tags on 15 zebra sharks were used to confirm that
pigmentation patterns were unique and persistent in wild zebra sharks for up to 810 d. Pollock’s robust design resulted in an annual population estimate of 458 individuals (95% CI = 298–618). The mean number of zebra sharks observed on a single day was 8 (± 8 SE) and the maximum number of zebra sharks seen on a single day was 34. In total, 27% of the sharks were sighted in more than
one summer aggregation period and males had greater re-capture probabilities than females. The aggregation consisted exclusively of large (>1800 mm total length) adults with an overall female sex bias of 3.8:1 though sex-ratios varied temporally. Predictable visitation of large, presumably mature individuals to the site raises conservation concerns if aggregations of similar size and structure occur in regions where zebra sharks are fished.
Keyword Mark-recapture
Seasonal aggregation
Zebra shark
Stegostoma fasciatum
Photo-identification
Abundance
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Mon, 02 Feb 2009, 12:21:23 EST by Gail Walter on behalf of School of Biological Sciences