Was downloaded from ASIH site in Feb 2010~
MOLLET, HENRY F.
Moss Landing Marine Laboratories, Moss Landing, CA 95039-9647, USA
Elasticity patterns for birds, mammals, turtles, and sharks: The importance of age at first reproduction, mean age of reproducing females, and survival in the discounted fertilities of the Leslie matrix
The elasticity pattern (E-pattern) of an age-structured animal comprising the elasticities E(fertility, m), E(juvenile survival, Sj) and E(adult survival, Sa) is determined by age at first reproduction (α) and mean age of the reproducing females at the stable age distribution (A-bar). The E-patterns of sharks, and marine turtles are characterized by A-bar/α ratios < 2.0 [E(Sa)/E(Sj) < 1] and a proportional change in juvenile survival has the largest effect on population growth (α). Marine birds and mammals generally have A-bar/α ratios > 2.0 and adult survival has the largest effect on population growth. Terrestrial birds, mammals, and turtles show a large range of A-bar/α ratios. The fast-slow continuum concept is not useful to understand E-patterns of these animals in the context of a prospective elasticity analysis with the goal of providing management proposals. It is important to include the survival part in the discounted fertilities of the Leslie matrix when calculating the E-pattern, otherwise post- and pre-breeding census will yield different and biased E-patterns. This bias is largest for animals with = 1 yr. The sum of the E-pattern is 1 + E(m) and has to be normalized when graphed in an elasticity triangle for easy interpretation. Assuming age-independent m and Sa, a new 3-term algebraic equation for A-bar facilitates the understanding and interpretation of E-patterns.