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Previous experience with M-type dart tags suggested that their implantation causes trauma and retards growth of small sharks. To test this hypothesis, we marked a group of 76 juvenile lemon sharks Negraprion brevirostris of a precaudal length of less than 80 cm with tiny (2 mm × 11 mm), passive integrated transponder (PIT) microtags, implanted intramuscularly. A second group of 563 lemon sharks of the same size range was marked with M-type dart tags, and both groups were released around Big Pine Key in Florida Bay. Growth of 10 recaptured fish with the M-type tag averaged 8.6 ± 2.34 (SD) cm/year, compared with an average of 17.1 ± 4.25 cm/ year for 10 recaptured fish with PIT tags. Growth of the PIT-tagged group was significantly greater (P < 0.001) than that of the dart-tagged group (one-way ANOVA). We recommend that biologists refrain from marking young or small sharks with M-type dart tags, especially for age and growth studies.
Manire et al. (Fri,) studied this question.