© 2006 International Council for the Exploration of the Sea
Preliminary observations of tag shedding, tag reporting, tag wounds, and tag biofouling for raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa
a Port Elizabeth Museum PO Box 13147, Humewood 6013, South Africa
b Department of Ichthyology and Fisheries Science, Rhodes University PO Box 94, Grahamstown 6140, South Africa
*Correspondence to M. L. Dicken: tel: +27 41 584 0650; fax: +27 41 584 0661. e-mail: raggedtoothshark{at}bayworld.co.za.
A double-tagging experiment and integrated on-site questionnaire and telephone survey were used to investigate aspects of tag shedding, tag reporting, tag wounds, and tag biofouling for the raggedtooth shark (Carcharias taurus), tagged off the east coast of South Africa. Between 2002 and 2004, 84 juvenile (<1.8 m total length, TL), and 24 adult (>1.8 m TL) C. taurus were double-tagged. Of these, 11 juvenile and six adult double-tagged sharks were recaptured. Significantly, more tags were shed from adult than from juvenile sharks, and there was also a significant difference between the number of anterior and posterior tags shed. Rates of tag reporting were estimated from a survey of 477 randomly selected shore-anglers, and they varied both temporally and spatially from 27% to 100%. In all, 93 tag recaptures were reported in the survey, most (75.3%) with some biofouling. Tag-inflicted damage was reported in 35.5% of recaptured sharks, and the incidence of tag-inflicted damage was greater for disk (77.8%) than for dart tags (25.3%).
Keywords: biofouling, Carcharias taurus, South Africa, tag reporting, tag shedding, tag wound
Received 10 February 2006; accepted 22 June 2006.