Precision and Bias of Three Bigmouth Buffalo Aging Structures

Abstract

AbstractThe Bigmouth Buffalo Ictiobus cyprinellus is a long‐lived catostomid with ecological and commercial harvest value. Management of Bigmouth Buffalo relies on accurate age data for population dynamic assessments (recruitment, growth, and mortality), but between‐reader precision of nonlethal aging structures compared to otoliths has not been assessed. We analyzed age bias and between‐reader precision of ages estimated from pectoral and dorsal fin rays relative to lapillus otoliths for Bigmouth Buffalo (n = 115) captured from shallow natural lakes in Iowa. Maximum agreed age was 21 years for otoliths, 15 years for pectoral fin rays, and 14 years for dorsal fin rays. Ages estimated from pectoral fin rays were the most precise (CV = 12.6%; average percent error [APE] = 8.9%), followed by dorsal fin rays (CV = 16.1%; APE = 11.4%) and otoliths (CV = 21.5%; APE = 16.5%). Pectoral fin rays also had higher exact agreement between readers (37%) and higher agreement within 1 year (77%) compared to dorsal fin rays (35% exact; 69% within 1 year) and lapillus otoliths (17% exact; 61% within 1 year). Both dorsal fin rays and pectoral fin rays underestimated age relative to otoliths, which resulted in younger population age structures and larger mean length‐at‐age estimates. Our results suggest that biologists can use dorsal and pectoral fin rays as viable nonlethal structures for younger fish (up to 10 years for dorsal fin rays; up to 13 years for pectoral fin rays), whereas otoliths can be difficult to age but are necessary to accurately determine age for older individuals.