Size‐Dependent Effects of Coded Wire Tags on Mortality and Tag Retention in Redtail Culter Culter mongolicus

Abstract

AbstractRedtail culter Culter mongolicus, a threatened piscivorous fish species in China's inland waters, has exhibited serious population decline. As part of a stock enhancement research project in shallow lakes of the Yangtze River basin, China, we evaluated the performance of coded wire tags (CWTs) for marking juvenile redtail culter. Through a short‐term indoor experiment, we marked hatchery‐reared juveniles from three size groups (mean ± SE, small: 46.85 ± 0.67 mm, intermediate: 53.76 ± 0.62 mm, large: 63.42 ± 1.05 mm) in the dorsal muscle with CWTs and tested whether marking effects on tag retention and mortality were size‐specific. Tag retention was more than 98% in all the three size groups and appeared to be unaffected by fish size. Tag losses were found only within 3 d of marking. Tagging‐induced mortality of small marked juveniles (58%) was significantly higher than those of intermediate (5%) and large (1%) marked juveniles and was also significantly higher than small unmarked ones (17%). The relationship of marked mortality and total length was quantitatively described by an exponential decay model. Mortality in small marked juveniles occurred mainly within 24 h after marking, which accounted for 71% of the mortality in this marked size. In order to avoid high posttagging mortality and biases in stocking assessment programs, we suggest it is worth the extra fish‐culture costs to use juveniles of at least 57 mm (which displayed 90% survival in our experiment) for stocking assessment programs that utilize CWTs for a handling‐sensitive species like redtail culter.Received December 1, 2011; accepted June 28, 2012