US Fish & Wildlife Service
Validation of three back-calculation models by using multiple oxytetracycline marks formed in the otoliths and scales of bluegill × green sunfish hybrids
Date of this Version
We assessed the accuracy of the Fraser–Lee, biological-intercept, and Weisberg back-calculation models to estimate growth from otoliths and scales of laboratory-reared juvenile bluegill × green sunfish hybrids (Lepomis macrochirus × Lepomis cyanellus). Hybrid sunfish were injected three times with oxytetracycline hydrochloride at 90- day intervals to mark bony structures, creating simulated annuli for model validation. Back-calculated lengths (BCLs) with otoliths were generally less accurate than scales for all three models. Errors ranged from –8.2 to 7.8% for the Fraser–Lee model, from –8.0 to 8.3% for the biological-intercept model, and from –6.5 to 14.3% for the Weisberg model. For all three models, there was no significant difference in BCLs using left or right otoliths, and BCLs using the Fraser–Lee and biological-intercept models were not significantly different from each other. In contrast with otoliths, all three models produced accurate BCLs from scales; errors ranged from –4.3 to 0.1%. For juvenile hybrid sunfish, we recommend using scales for back-calculation of growth. The Fraser–Lee (with zero intercept) and biologicalintercept models produced the most accurate BCLs from otoliths. However, due to potential decoupling of otolith and body growth, caution should be exercised when estimating juvenile hybrid sunfish growth from otoliths.
Published in Can. J. Fish. Aquat. Sci. 58: 352–364 (2001) © 2001 NRC Canada 352 DOI: 10.1139/cjfas-58-2-352