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Do dart tags suppress growth of dusky kob <i>Argyrosomus japonicus</i>?


MH Griffiths
CG Attwood

Abstract

Growth rates of dusky kob Argyrosomus japonicus calculated from mark-recapture and otolith-reading methods were compared. Mark-recapture data showed that A. japonicus are resident in an area between the Breede River Estuary and Cape Agulhas on the southeast coast of South Africa. Maximum recapture length was 1 150mm. A von Bertalanffy growth curve, fitted to length-at-age data derived from otolith sections of 168 specimens (1–42 years) from the Breede Estuary and adjacent marine environment, was differentiated to provide instantaneous length-based growth rates. Comparison of mark-recapture and otolith-based growth rates revealed that external dart tags suppress growth of A. japonicus <750mm, but do not affect the growth of larger fish.

Keywords: growth rate; mark-recapture; movement; otolith sections

African Journal of Marine Science 2005, 27(2): 505–508
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eISSN: 1814-2338
print ISSN: 1814-232X