Red sea urchins (Strongylocentrotus Walters, 1992; Congdon et al., 1994; franciscanus) along the west coast of Ebert, 1998). There is also the need to North America, like most large sea understand the evolution of life histo-urchins in temperate waters world-ries of species where long life tends to wide, are the focus of a commercially be an indicator of uncertainty in indi-important fishery. In a review of bio-vidual reproductive success (Murphy, logical data for purposes of fishery 1968; Roff, 1992; Stearns, 1992). management, the life span of red sea Enhanced radiocarbon in the oceans urchins was suggested to be 7–10 due to atmospheric testing of nuclear years (Sloan, 1986) and they have weapons that began in the 1950s (Ny-been included with much shorter-lived dal and Lovseth, 1983; Broecker et species for illustrating complex popula-al., 1985, Duffy et al., 1995) provides tion dynamics (Hastings and Higgins, a permanent marker in carbonate-1994). Recent work with tetracycline based skeletal elements that are not and calcein tagging (Ebert, 1998; Ebert reworked by resorption and deposition et al., 1999), however, has shown that during growth and hence has a long individuals continue to grow through-time period between mark and recov-out life, although at a very slow rate, ery. The enhanced radiocarbon marker and large individuals are estimated to has been used in various studies to be in excess of 100 years old. A poten-validate the periodic (usually annual) tial problem with the studies using nature of growth zones in fish (Kalish, tetracycline and calcein is that one-1993, 1995; Campana, 1997; Campana year time intervals were used between et al., 2002) and invertebrates (Tureki-tagging and recapture and therefore it an et al., 1982; Witbaard et al., 1994; is possible that occasionally there may Peck and Brey, 1996) where validation have been very good years for growth by chemical tags such as tetracycline that were missed. If occasional growth has been impractical. Red sea urchins spurts occurred, largest sizes would lack interpretable growth zones (Breen have been attained in much less than and Adkins, 1976) and therefore there 100 years. The potential problem of is no natural feature to serve as a cross missed good years for growth could be check for studies using chemical tags. resolved with a marker that captures In the present study we present a test a longer period of time. The accuracy and confirmation of age in red sea of age estimates has consequences urchins estimated from tetracycline for resource management where size tagging using an enhanced 14 C signal limits may need adjustment in order to in the ocean from nuclear weapons protect older individuals (Hilborn and testing. Materials and methods Red sea urchins were tagged with tet-racycline from 1989 to 1992 in northern California, Oregon, and Washington and collected after time intervals of approximately one year (details pre-sented in Ebert et al., 1999). It is not possible to determine whether a live sea urchin has a tetracycline mark and therefore large collections had to be made. Skeletal elements were cleaned with sodium hypochlorite bleach to remove all organic material not bound in the calcite of the skeleton, and then skeletal ossicles were exam-ined by using UV illumination to detect the tetracycline marks, which fluoresce yellow. Growth increments were mea-sured in jaws of Aristotle's lantern of 1582 tagged-recovered red sea urchins and used to estimate growth parame-ters. Jaw ossicles, the demipyramids of Aristotle's lantern, are internal skeletal elements that grow around all surfaces but not equally in all directions so that a change in jaw length, ∆J, is mostly at the end closest to the esophagus and there is little growth closest to the mouth, the labial end, where the teeth extend from the jaw. The Tanaka function (Eq. 1) was used to describe growth (Tanaka, 1982, 1988) because it can model data that show an initial lag, an exponential phase with a maximum, and can include continuing growth throughout life. This function is described in greater detail else-where (Tanaka, 1982, 1988; Ebert et al., 1999). The usual formulation of the Tanaka model is ∆size as a function of size at time t and ∆t is assumed to be fixed for all individuals in the sample, usually at ∆t = 1 year (Tanaka, 1982, 1988; Ebert, 1998; Ebert et al., 1999) and not included explicitly in the equa-tion. In the present study we estimated the amount of jaw that would have to be removed to represent the time span from the time of collection in the 1990s with relatively high 14 C levels to the time before atmospheric testing of atomic bombs (relatively low 14 C) and Manuscript approved for publication 10 July 2003 by Scientific Editor.