Otoliths (asteriscus) have been validated as an accurate structure for estimating age of common carp Cyprinus carpio. However, extraction and processing of common carp otoliths are time consuming and require sacrifice of fish. Therefore, we analyzed age estimation precision of four alternative structures relative to otolith age for 139 common carp collected from five eastern South Dakota lakes. All common carp were collected using daytime electrofishing. Each fish was assigned an identification number and measured to the nearest millimeter total length, after which aging structures were removed. Age was estimated from scales, vertebrae, opercles, pectoral fin rays, and asteriscus otoliths by methods similar to those recommended by previous researchers. Relative to otolith age, average percent error was 6.8% for scales, 15.4% for vertebrae, 9.9% for opercles, and 1.2% for pectoral fin rays. Compared with all other structures, ages from pectoral fin ray sections were nearly as precise as otoliths through age 13 (lowest average percent error); however, fin rays consistently underestimated the ages of fish older than 13 years. In most cases, pectoral fin ray ages matched otolith ages, thereby providing similar age estimates. We conclude that pectoral fin rays provide a precise, economical, and nonlethal alternative for estimating common carp age structure. Accuracy of common carp ages estimated from pectoral fin rays still requires evaluation.

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Gizzard shad, Dorosoma cepedianum, have generally been restricted to the lower Missouri River impoundments in South Dakota. In recent years, gizzard shad numbers have increased in Lake Oahe, marking the northernmost natural population. These increases could potentially affect recreational fishes. Specifically, questions arise about larval gizzard shad growth dynamics and if age-0 gizzard shad in Lake Oahe will exhibit fast or slow growth, both of which can have profound effects on piscivore populations in this reservoir. In this study, we evaluated larval gizzard shad hatch timing, growth, and density in Lake Oahe. We collected larval gizzard shad from six sites from May to July 2008 and used sagittal otoliths to estimate the growth and back-calculate the hatch date. We found that larval gizzard shad hatched earlier in the upper part of the reservoir compared to the lower portion and that hatch date appeared to correspond to warming water temperatures. The peak larval gizzard shad density ranged from 0.6 to 33.6 (#/100 m 3 ) and varied significantly among reservoir sites. Larval gizzard shad growth ranged from 0.24 to 0.57 (mm/d) and differed spatially within the reservoir. We found no relationship between the larval gizzard shad growth or density and small-or large-bodied zooplankton density (p 4 0.05). As this population exhibits slow growth and low densities, gizzard shad should remain a suitable forage option for recreational fishes in Lake Oahe.