Dear colleagues,

A new paper on demographic assessment of California sea lions was recently published in Ecological Applications. [The paper was also featured in the ESA Bulletin art gallery (year 2008, vol 89, pp 221-222)]

You can send PDF requests to: manuela.gonzalez@asu.edu

Jeffrey Wielgus, Manuela Gonzalez-Suarez, David Aurioles-Gamboa, and Leah R, Gerber (2008). A NONINVASIVE DEMOGRAPHIC ASSESSMENT OF SEA LIONS BASED ON STAGE-SPECIFIC ABUNDANCES. Ecological Applications 18 (5): 1287–1296.

Abstract. A pressing need exists to develop new approaches for obtaining information on demographic rates without causing further threats to imperiled animal populations. In this paper, we illustrate and apply a data-fitting technique based on quadratic programming that
uses stage-specific abundance data to estimate demographic rates and asymptotic population growth rates (k). We used data from seven breeding colonies of California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Estimates of k were similar to those from previous studies relying on a diffusion approximation using trends in total abundance. On average, predicted abundances were within 24% of the observed value for the inverse estimation method and within 29% of the observed value for the diffusion approximation.
Our results suggest that three of the seven populations are declining (k , 1), but as many as six may be at risk. Elasticity and sensitivity analyses suggest that population management in most sites should focus on the protection of adults, whose survival generally contributes the most to k. The quadratic programming approach is a promising noninvasive technique for estimating demographic rates and assessing the viability of populations of imperiled species.

Thanks
Manuela

--
"I have never let my schooling interfere with my education"
Mark Twain
Manuela Gonzalez
SOLS Biology Graduate Program
P.O Box 874601 ASU Tempe, AZ 85287-4601
http://www.public.asu.edu/~lrgerbe/manuela.htm