Effects of subcutaneous microtags on the growth, survival, and vulnerability to predation of small reef fishes

Marking reef fish with small, subcutaneous tags has proven to be a useful technique in ecological studies in both temperate and tropical systems. However, such tags may have adverse impacts on tagged individuals, possibly biasing estimates of demographic rates. We used field experiments on natural and artificial patch reefs to test for effects of subcutaneous acrylic paint and visual implant (VI) tags on the growth and mortality of the tropical goby Coryphopterus glaucofraenum (Gill). Growth of small (< similar to 35 mm TL) C. glaucofraenum marked with acrylic paint was slower than that of similarly sized fish marked with VI tags, but growth of larger (> similar to 35 mm TL) fish was unaffected by tagging method. Neither acrylic paint, nor VI tags, influenced the mortality of C. glaucofraenum. We also conducted experiments in large outdoor tanks to test whether visual implant fluorescent elastomer (VIE) tags increased the susceptibility to predation of two temperate gobies, Coryphopterus nicholsii (Bean) and Lythrypnus dalli (Gilbert). For both goby species, tagged fish were no more susceptible to predatory kelp bass, Paralabrax clathratus (Girard) than untagged fish. Overall, with the exception of the slight reduction in growth of small C. glaucofraenum caused by acrylic paint tags, our results indicate that internal microtags can provide an effective means of marking small reef fish without introducing significant artifacts. (C) 1999 Elsevier Science B.V. All rights reserved.