Skip to main content
Open Access Publications from the University of California

UC Davis

UC Davis Previously Published Works bannerUC Davis

Modeling Red Sea Urchin Growth Using Six Growth Functions


ABSTRACT The growth of red sea urchins, Strongylocentrotus franciscanus, was modeled using tag/recapture data from northern California. Red sea urchins (N = 211) ranging in test diameter from 7 to 131 mm, were examined for changes in size over one year. We used the function Jt+1 = Jt + f(Jt) to model growth, in which Jt is the jaw size (mm) at tagging, and Jt+1 is the jaw size one year later. The function f(Jt), represents one of six deterministic models: Logistic dose response, Gaussian, Tanaka, Ricker, Richards, and von Bertalanffy with 3, 3, 3, 2, 3, and 2 minimization parameters, respectively. We found that three measures of goodness of fit ranked the models similarly, in the order given. The results from these six models indicate that red sea urchins are slow growing animals with a mean of 7.2 1.3 years to enter the fishery. We show that poor model selection and/or data from a limited range of urchin sizes produces erroneous growth parameter and years to fishery estimates. Individual variation in growth dominated spatial variation at shallow and deep sites (F = 0.246, N = 199, p = 0.62). We summarize the six models using a composite growth curve of jaw size, J, as a function of time, t J = A(B – e-Ct) + Dt in which each model is distinguished by the constants A, B, C, and D. We suggest that this composite model has the flexibility of the other six models and could be broadly applied. Given the robustness of our results regarding the number of years to enter the fishery, this information could be incorporated into future fishery management plans for red sea urchins in northern California.

Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies. Let us know how this access is important for you.

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View