Steven Campana delivers a lecture

The age determination of many long-lived fish species is often based on otolith cross-sections. However, the age determination of Sebastes species (redfish or ocean perch) has been mired in “traditional” methods for decades, some of which produce wildly inaccurate results. Here I report substantial improvements in the tried and true “break and burn” method for ageing Sebastes spp through modern sectioning and image enhancement protocols. Otolith halves sectioned with an Isomet saw allowed routine preparation of completely flat surfaces for charring, while imaging and image enhancements significantly improved the visibility of narrow growth bands in older fish. Bomb radiocarbon assays of the otolith core confirmed the accuracy of the resulting age determinations; redfish can live for at least 70 years. The use of microsatellite DNA to confirm species identity eliminated past confusion due to species mixtures. Even within species and stocks, an individual fish with a fork length of 38 cm could be anywhere between 15 and 50 years of age, highlighting the fact that growth nearly stops after sexual maturation. Modern image analysis techniques can make almost all fish age determinations easier, and some of the same methods are also applicable to recreational photographs.