Growth and mortality of red sea urchins Strongylocentrotus franciscanus across a latitudinal gradient

Growth and survival of the red sea urchin Strongylocentrotus franciscanus w ere studied at 18 sites from southern California to Alaska, USA. Growth was determined using tetracycline tagging and was modeled using the Tanaka gro wth equation. Survival rates were estimated using size-frequency distributi ons and growth parameters. Using log-linear analysis, it was determined tha t growth transitions differed among sites (p much less than 0.001) but ther e was no north-south difference (p > 0.80). Parameters for the Tanaka growt h function were estimated for all data combined (N = 2714). Residuals for s ites showed no latitudinal trend and so results were consistent with the lo g-linear analysis. Relative jaw (demi-pyramid) size, measured as the allome tric exponent beta in jaw length as a function of test diameter, has been s hown to be responsive to available food. For red sea urchins, beta was nega tively correlated with growth but there was no correlation of relative jaw size with latitude, which suggests that latitudinal differences in food ava ilability do not exist. In contrast with annual growth rates, annual surviv al rates were correlated with latitude and were higher in the north. Mean a nnual survival probability was 0.93 yr(-1) from northern California to Alas ka and 0.77 yr(-1) in southern California. Likely causes for changes in sur vival rate with latitude are disease and temperature-related stress. This p aper provides the basis for development of hypotheses for size and survival differences between northern and southern populations of red sea urchins a nd, potentially, for other marine species with planktonic larvae.