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 t echnique in ecological studies in both temperate and tropical systems. Howe ver, such tags may have adverse impacts on tagged individuals, possibly bia sing estimates of demographic rates. We used field experiments on natural a nd artificial patch reefs to test for effects of subcutaneous acrylic paint and visual implant (VI) tags on the growth and mortality of the tropical g oby Coryphopterus glaucofraenum (Gill). Growth of small (< similar to 35 mm TL) C. glaucofraenum marked with acrylic paint was slower than that of sim ilarly sized fish marked with VI tags, but growth of larger (> similar to 3 5 mm TL) fish was unaffected by tagging method. Neither acrylic paint, nor VI tags, influenced the mortality of C. glaucofraenum. We also conducted ex periments in large outdoor tanks to test whether visual implant fluorescent elastomer (VIE) tags increased the susceptibility to predation of two temp erate 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 introduci ng significant artifacts. (C) 1999 Elsevier Science B.V. All rights reserve d.