TitleMortality estimates from age distributions: Critique of a method used to study seagrass dynamics
Publication TypeJournal Article
Year of Publication2002
AuthorsEbert, TA, Williams, SL, Ewanchuk, PJ
JournalLimnology and Oceanography
Keywordsflorida bay USA thalassia-testudinum population-dynamics growth productivity demography biomass decline forest

Age structure of seagrass samples has been used to estimate survival and recruitment and then used to estimate population growth rate. Survival rate can be estimated from age structure only if the population is neither growing nor declining (r = 0), so the age distribution is both stable and has stationary structure. If survival is estimated from age structure, it must be assumed that r = 0 or additional information about the population must be known. If a decaying exponential model is used for number (N) in each age class, In N versus age has a slope of -(M + r), and so an incorrect survival rate, exp (-M), would be estimated if r not equal 0. Simulations show that when r > 0, the slope of the regression of In N versus age is too steep and hence mortality rate would be overestimated, and the reverse when r