Department of Marine Ecology, University of Gothenburg, Sweden.
Ambio. 2011 Feb;40(1):52-9. doi: 10.1007/s13280-010-0091-7.
Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.
丰度估计的时间序列通常用于分析种群趋势和增长率可能的变化。我们研究了年龄结构的趋势是否可以替代丰度估计来检测种群增长的减缓。在波罗的海灰海豹生长的模拟时间序列中，这两种方法分别在两种形式的密度依赖性和不同水平的环境变化下进行了测试。在逻辑斯谛增长下，基于种群数量的统计结果显示，在 16 年后可以确认生长减缓，而基于年龄结构的统计结果显示在 14 年后可以确认生长减缓。当密度依赖性首先在较大的种群规模上出现时，年龄结构法的表现明显优于种群数量法，并且可以在 4 年后（而不是 10 年后）检测到下降。因此，年龄结构分析提供了一种检测密度依赖性的补充方法，特别是在密度依赖性出现较晚的种群中。
