Comparison of Calcified Structures for Aging Spotted Seatrout

Abstract

Aging structures for spotted seatrout Cynoscion nebulosus have been compared for the first time by using sectioned pectoral fin rays, sectioned dorsal fin spines, scales, and whole and sectioned otoliths from 50 fish of 300 to 731 mm total length. We considered the following criteria: processing time, reader confidence, reader agreement (precision), agreement of mark counts between structures, and growth with presumed age. Processing time—more than 1 h per fish—was unreasonably high for sectioned pectoral fin rays, so we did not evaluate their use further. Sectioned dorsal fin spines were clear and easy to read, but mark counts disagreed with those of other structures and were not significantly related to the growth of the fish or that of the aging structure. Scale marks often were inconsistent, which led to low confidence and low agreement between readers. Scale ages also showed systematic disagreement with sectioned-otolith ages. Reader confidence was relatively low for whole-otolith age readings in comparison with sectioned readings of the same otolith, and whole-otolith ages showed systematic disagreement with sectioned-otolith ages. Sectioned otoliths were far superior to all other structures in all criteria: marks were clearest, reader confidence was highest, agreement was 100% both within and between readers, and both fish size and structure size increased significantly with presumed age. Consequently, we recommend that sectioned otoliths be the preferred structure for determining the age of spotted seatrout.

Notes

¹ Brown (1981), using scales, reported a 15-year-old spotted seatrout from the Chesapeake Bay that measured 776 mm TL and weighed 5,443 g. This scale age may be inaccurate, however, since a fish this length and weight would correspond to only an 8.7-year-old spotted seatrout aged with sectioned otoliths in our 1996–1999 collection from the Chesapeake Bay.