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Beaufort Laboratory Southeast Fisheries Science Center National Marine Fisheries Service 101 Pivers Island Road Beaufort, North Carolina 28516 Abstract—Age determination is import ­ ant for estimating productivity and status in fisheries stock assessments. Aging methods must balance advances in technology with continuity of data for long­ term sampling programs. The long­ term sampling program for Atlantic menhaden (Brevoortia tyrannus) and Gulf menhaden (B. patronus) has resulted in a database of ages that were determined by using an Eberbach projector, a now outdated technology. The objective of this study was to com­ pare ages determined with an Eberbach projector to those determined with a more recent technology, the ste­ reo microscope. Scales from Atlantic (total number of fish [N]=1317) and Gulf menhaden (N=1569) were aged by using both an Eberbach projector and a stereo microscope, and results were compared by using percent agree­ ment, average percent error, Chang’s average coefficient of variation, bias tests, and simultaneous multinomial confidence intervals. The results from these measures for comparing age esti­ mates were generally within standard, expected levels. Some bias was detected between estimates from the use of the 2 devices but was likely due to the use of poorly preserved scales or images of low quality on the Eberbach projector. Our results indicate that the use of a micro­ scope will help maintain continuity in age estimates over time for long­ term monitoring and for stock assessments.

fishery bulletin

Comparison of ages determined by using an Eberbach projector and a microscope to read scales from Atlantic menhaden (Brevoortia tyrannus) and Gulf menhaden (B. patronus): suppl. figs. 1-6