Measuring fish condition: an evaluation of new and old metrics for three species with contrasting life histories

Measuring fish condition should link ecosystem drivers with population dynamics, if the underlying physiological basis for variations in condition indices are understood. We evaluated traditional (K, Kn, hepatosomatic index, gonadosomatic index, energy density and percent dry weight of muscle [%DWM] and liver [%DWL]) and newer (bioelectrical impedance analysis [BIA] and scaled mass index [SMI]) condition indices to track seasonal cycles in three flatfishesâ winter (3 stocks), yellowtail (3 stocks), and summer flounder (1 stock) â with contrasting life histories: in habitat, feeding, and reproduction. The %DWM and %DWL were good proxies for energy density (r2 > 0.96) and more strongly related to K, Kn and SMI than to BIA metrics. Principal component analysis indicated many metrics performed similarly across species; some confounded by size, sex, and maturity along PC1, others effectively characterizing condition along PC2. Stock differences were along PC1 in winter flounder, reflecting different sizes across stocks, whereas in yellowtail flounder differences occurred along PC2 related to condition. These comparisons, within and across species, highlight the broad applicability of some metrics and limitations in others.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author